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Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001–2008

Victor L Fulgoni III 1 ,
Mark Dreher 2 &
Adrienne J Davenport 3

Nutrition Journal volume 12 , Article number: 1 ( 2013 ) Cite this article

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Avocados contain monounsaturated fatty acids (MUFA) dietary fiber, essential nutrients and phytochemicals. However, no epidemiologic data exist on their effects on diet quality, weight management and other metabolic disease risk factors. The objective of this research was to investigate the relationships between avocado consumption and overall diet quality, energy and nutrient intakes, physiological indicators of health, and risk of metabolic syndrome.

Avocado consumption and nutrition data were based on 24-hour dietary recalls collected by trained NHANES interviewers using the USDA Automated Multiple Pass Method (AMPM). Physiological data were collected from physical examinations conducted in NHANES Mobile Examination Centers. Diet quality was calculated using the USDA’s Healthy Eating Index-2005. Subjects included 17,567 US adults ≥ 19 years of age (49% female), including 347 avocado consumers (50% female), examined in NHANES 2001–2008. Least square means, standard errors, and ANOVA were determined using appropriate sample weights, with adjustments for age, gender, ethnicity, and other covariates depending on dependent variable of interest.

Avocado consumers had significantly higher intakes of vegetables (p < 0.05); fruit, diet quality, total fat, monounsaturated and polyunsaturated fats, dietary fiber, vitamins E, K, magnesium, and potassium (p < 0.0001); vitamin K (p = 0.0013); and lower intakes of added sugars (p < 0.0001). No significant differences were seen in calorie or sodium intakes. Body weight, BMI, and waist circumference were significantly lower (p < 0.01), and HDL-C was higher (p < 0.01) in avocado consumers. The odds ratio for metabolic syndrome was 50% (95th CI: 0.32-0.72) lower in avocado consumers vs. non-consumers.

Conclusions

Avocado consumption is associated with improved overall diet quality, nutrient intake, and reduced risk of metabolic syndrome. Dietitians should be aware of the beneficial associations between avocado intake, diet and health when making dietary recommendations.

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Dietary guidelines around the world recommend increased consumption of fruit and vegetables because they have low-to-medium energy density and are important contributors of major shortfall nutrients including dietary fiber, vitamins A, C and K, magnesium, and potassium [ 1 , 2 ]. Fruit and vegetables contain a diverse mixture of phytochemicals that may help support health and wellness and potentially reduce the risk of chronic diseases [ 3 ]. Data indicate that in the US, <3% of men and <6% of women aged 19 to 50 years consume the number of daily fruit and vegetable servings recommended [ 4 , 5 ].

Hass avocado ( Persea americana ) is a medium-size fruit with a pleasant, creamy, smooth texture. About 90% of the avocados consumed in the US and a majority of avocados worldwide are Hass avocados [ 5 ]. The avocado is a medium energy dense (1.7 kcal/g) fruit because it contains about 80% water and dietary fiber. Unlike other fruits, avocados are low in sugar and contain 15% MUFA rich oil, which helps to increase the bioavailability of carotenoids from salads and salsa often consumed with avocados [ 5 – 8 ]. Avocados also contain a variety of vitamins, minerals and phytochemicals such as lutein, phenolic antioxidants, and phytosterols associated with numerous potential health benefits [ 5 , 7 , 8 ]. Although there are 8 preliminary clinical studies on avocado and cardiovascular health [ 9 – 16 ], research on avocado health benefits is limited. The purpose of this study was to for the first time investigate associations between avocado consumption and diet quality, energy and nutrient intakes, body weight and metabolic syndrome risk factors in a nationally representative sample of US adults.

NHANES is an ongoing initiative conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention to collect information on the health and nutritional status of a nationally represented cross-sectional sample of the total civilian, noninstitutionalized US population. The NHANES design is a stratified, multistage probability sample based on selection of counties, blocks, households, and the number of people within households. In 1999, the survey became a continuous program with a changing focus on a variety of pertinent health and nutrition measurements [ 17 ]. The methods and study design for NHANES have been previously described [ 18 , 19 ]. Data from 24-hour dietary recalls were collected using the Automated Multiple-Pass Method (AMPM) [ 20 ]. The Day 1 interview was conducted in person in a Mobile Examination Center (MEC) and was used for this study.

Energy and nutrient intakes were calculated using the United States Department of Agriculture (USDA) Food and Nutrient Database for Dietary Studies (FNDDS) versions 1.0 [ 21 ] 2.0 [ 22 ] and 3.0 [ 23 ]. NHANES uses the FNDDS to process and analyze dietary recall data. These databases have been previously described [ 24 ].

We used the MyPyramid Equivalents Database (MPED) versions 1.0 [ 25 ] and 2.0 [ 26 ] to examine consumption in terms of MyPyramid now called MyPlate [ 27 ] servings (hand matching foods without values in more recent NHANES surveys). The MPED translates dietary recall data into equivalent servings of the seven MyPlate major food groups and corresponding subgroups. The number of MyPlate servings was based on the 24-hr food dietary recall data from NHANES 2001–2008 participants. Avocado consumers were identified as NHANES 2001–2008 participants who reported eating any amount of avocado during the 24-hour dietary recall.

Diet quality was calculated using the USDA’s Healthy Eating Index (HEI)-2005 [ 28 – 30 ]. The HEI-2005 is a measure of diet quality that indicates how closely diets adhere to the 2005 Dietary Guidelines for Americans, and is primarily used by the USDA to monitor the diet quality of the US population. The original HEI was created in 1995 and revised in 2006 to reflect the 2005 Dietary Guidelines for Americans. Food group standards [ 31 ] and the development and evaluation of the HEI-2005 have been previously described [ 32 , 33 ].

Health indices evaluated included body weight, body mass index (BMI), waist circumference, HDL cholesterol (HDL-C), and risk of metabolic syndrome. The latter was defined as the presence of three or more of the following components: waist circumference ≥ 40 in (102 cm) for males or ≥ 35 in (88 cm) for females; triglycerides ≥ 150 mg/dL; HDL-C <40 mg/dL for males and < 50 mg/dL for females; blood pressure ≥ 130/85 mm Hg; or fasting glucose ≥ 100 mg/dL [ 34 ].

Least square means, standard errors of the mean, and ANOVA were determined for avocado consumption, diet quality, energy and nutrient intakes, and physiological markers of metabolic disease risk (ie, body weight, BMI, waist circumference, and HDL-C) in avocado consumers and non-consumers. The results were weighted using the NHANES examination sample weights to produce national estimates and adjust for the complex sample design of NHANES. Diet quality and food group/nutrient intakes were adjusted for age, gender, ethnicity, poverty income ratio, self-reported physical activity level, smoking status, alcohol intake, and energy intake. Physiological variables were adjusted for age, gender, ethnicity, poverty income ratio, self-reported physical activity level, smoking status, alcohol intake and BMI (for non-weight related variables). Minimal statistical significance was set at p < 0.05. Data were analyzed with the statistical packages SAS version 9.2 (SAS Institute, Cary, NC) and SUDAAN version 10.0.1 (2009, RTI, Research Triangle Park, NC).

The NHANES 2001–2008 sample included 17,567 individuals ≥ 19 years of age (49% female). Data indicate that approximately 2% of individuals were avocado consumers (n = 347; 50% female). Mean avocado intake (Table 1 ) was 70.1 ± 5.4 g/d (approximately one half of a medium-sized fruit), which contains about 114 calories of which 95 calories come from fat [ 5 , 35 ]. Consumption of avocados was higher in males than females.

Compared to non-consumers, diet quality (Table 2 ) was significantly (p < 0.0001) higher in avocado consumers. The latter had significantly (p < 0.05) higher intakes of fruit and vegetables and lower intake of added sugars. There were no significant differences between consumers and non-consumers for intakes of total grains, whole grains, dairy, meat and beans, and discretionary fats (as oil or solid fat).

Compared with non-consumers, those who ate avocados (Table 3 ) had significantly (p < 0.0001) higher intakes of total fat, monounsaturated fat, polyunsaturated fat, dietary fiber, vitamin E, magnesium and potassium, and vitamin K (p = 0.0013). Avocado consumers had significantly lower carbohydrate (p < 0.001). No significant differences were seen in calorie or sodium intakes. Those who ate avocados had significantly (p < 0.01) lower body weight, BMI, and smaller waist circumference (Table 4 ). HDL-C was significantly (p < 0.01) higher in avocado consumers compared to non-consumers. The odds ratio for metabolic syndrome was 50% lower in those who ate avocados compared to those who did not (95% confidence interval [CI]: 0.34, 0.72).

This is the first report to investigate avocado consumption among the US population ≥ 19 years of age, and explore its relationships to diet quality, energy and nutrient intakes, and physiological markers of health. In this report, avocado consumption was associated with significant differences in diet quality and nutrient intakes, higher HDL-C levels, and lower body weight, BMI, waist circumference, and risk of metabolic syndrome. The improved diet quality, nutrient intake, and HDL-C outcomes associated with avocado consumption are consistent with the avocado composition and clinical data [ 5 , 9 – 16 ]. Since energy intake was not different between consumers and nonconsumers, the reported lower body weight, BMI and waist circumference for the avocado consumers needs to be further investigated. The effect of diets on weight control may be dependent of a number of factors such as energy density, macronutrient bioavailability, and potentially other factors such as food physical properties [ 36 – 38 ]. Epidemiological evidence and intervention studies generally support the association between the consumption of energy-dense/high-fat diets with being overweight [ 36 , 37 ]. Insulin resistance, a key pathogenic link underlying the cluster of metabolic abnormalities seen in metabolic syndrome, is adversely effected by saturated fat and improved with MUFA [ 39 – 41 ]. Tree nuts, which are similar to avocado in dry weight composition including dietary fiber and MUFA content, have not been shown to increase body weight or metabolic syndrome risk in numerous clinical and epidemiological studies [ 42 – 46 ].

Epidemiologic studies dating back to the 1970s show the health benefits of MUFAs [ 45 ]. The Seven Countries Study found that death rates were positively related to the average percentage of energy from saturated fatty acids (SFAs) and negatively related to the percentage of dietary energy from MUFAs [ 47 ]. Prospective studies of US nurses have demonstrated an estimated reduction of 19% in the risk of coronary disease when the intake of MUFAs is increased by 5% (as a percentage of total energy intake) [ 48 ]. More recently, Moreno et al. [ 49 ] found that a MUFA-rich diet may have favorable effects on cardiovascular risk by preventing the oxidative modifications of LDL-C and reducing macrophage uptake of plasma oxidized LDL. Studies also suggest that MUFAs may have a modest antihypertensive effect and could improve insulin sensitivity [ 40 ].

Results of this study indicate avocado consumption is associated with improved nutrient intakes including higher intake of mono- and polyunsaturated fat, dietary fiber and several vitamins and minerals; lower body weight, BMI, and waist circumference; higher HDL-C; and decreased risk of metabolic syndrome. These findings suggest a role for avocados in improving dietary quality and possibly reducing the risk of metabolic syndrome in the United States. Further research is needed to verify this epidemiological data and study the potential association between increased intake of avocados and other dietary components.

Limitations of the study

Energy and food group/nutrient intakes, including HEI-2005 scores, in this study were based on single 24-hour dietary recalls. While dietary recalls were collected via AMPM, the best methodology available, there are still limitations to this dietary collection method [ 24 ]. Recalls may be inaccurate and biased due to misreporting or memory lapses. Even though the AMPM method has been validated against weighed food records, energy can be underestimated by 3% for a population of normal weight and up to 11% for overweight and obese persons [ 18 , 24 ].

The present report comes from cross-sectional epidemiological data and thus cannot provide causal evidence between avocado consumption and improvements in diet quality, nutrient intakes, body weight, BMI, waist circumference, or indices of health. The number of avocado consumers was relatively small and while we used numerous covariates in an attempt to remove effects of other variables, residual confounding may still exist. The associations reported here should be interpreted accordingly.

This study is the first to explore associations between avocado consumption and diet quality, nutrient and energy intakes, and metabolic disease risk factors in a stratified random sample of the total civilian, noninstitutionalized US population. Use of NHANES estimates makes it possible to generalize findings to the population at large. The data demonstrate significant associations between avocado consumption and a higher HEI diet quality score and nutrient intakes; lower body weight, BMI, and waist circumference; higher HDL-C levels; and reduced risk of metabolic syndrome. Dietitians can recommend consumption of avocados as part of a healthful diet that focuses on increased fruit and vegetable intake. Avocados can be incorporated into the diets of most adults, and may be of additional benefit to those who have increased risk for metabolic disease risk factors.

This study was supported by the Hass Avocado Board.

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VLF as Senior Vice President of Nutrition Impact, LLC performs consulting and database analyses for various food and beverage companies and related entities. MD is a nutrition science consultant for various food companies and related entities including the Hass Avocado Board. AJD is an analyst for School Nutrition Programs within the Michigan Department of Education and also serves as a freelance nutrition consultant.

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VLF designed the study, was primarily responsible for the data analysis, and provided critical input into the manuscript; MD and AJD helped with data analysis and drafted the manuscript. All authors read and approved the final manuscript.

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Fulgoni, V.L., Dreher, M. & Davenport, A.J. Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001–2008. Nutr J 12 , 1 (2013). https://doi.org/10.1186/1475-2891-12-1

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Tanzania Journal of Science

agnes nyomora , Donatha Tibuhwa , Rodomiro Ortiz

Avocado is a healthy fruit and the consumption is continuously growing worldwide. The fruit contains polyphenolic compounds with antioxidant effects. Globally, research has been devoted to exploring the fruit quality, especially compounds with antioxidant effects, from different avocado-growing sites. However, the fruit quality of the Tanzanian avocado has so far not been investigated. In this study, the contents of polyphenols in peel, pulp and seed of avocados sampled in south-western Tanzania are described. The levels of total polyphenolic and flavonoid contents were measured, and antioxidant activity was evaluated using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The total polyphenolic content was highest in the seed and lowest in the peel (424 and 200 mg GAE/100 g DW, respectively). As for the total flavonoid content, the pulp had the highest value of 36.98 mg RE/100 g DW, while the seed had the lowest value of 32.54 mg RE/100 g DW. The overall average half maximal effective ...

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Perspective article, the forgotten fruit: a case for consuming avocado within the traditional mediterranean diet.

1 Avocado Nutrition Center, Mission Viejo, CA, United States
2 Independent Researcher, Valencia, CA, United States

The Mediterranean diet is rich in fruits and vegetables and includes an abundant intake of oleic-acid-rich olive oil. People who adhere to a Mediterranean diet have reduced risk for numerous chronic diseases. As obesity rates rise globally, people who choose to follow a traditional Mediterranean diet and/or make improvements in food choices may reduce their risk of metabolic dysfunction and disease. Incorporating non-traditional fruits and vegetables into the Mediterranean diet could provide greater flexibility in suitable food choices for people who struggle to adhere to recommended healthy dietary patterns, and it could also provide greater adaptability for people living outside of the Mediterranean region who are interested in adopting the diet. The avocado fruit thrives in a Mediterranean climate, is produced in the region, and is rich in oleic acid and fiber, yet avocados are not commonly consumed within the traditional Mediterranean diet. Based on the existing research studies on the health benefits of avocado consumption and the continued investigation into the nutritional attributes of the avocado, a case can be made for including avocados as part of the Mediterranean dietary pattern.

Introduction

Across the world, countries are experiencing major shifts in their food systems and diets that affect the nutritional status and health of their inhabitants. In the Mediterranean region, the traditional dietary pattern is mainly plant-based with (1) high consumption of vegetables, fruits, legumes, unrefined grains, nuts, and olive oil, (2) moderate intake of fish, wine, and fermented dairy products such as cheese and yogurt, and (3) low intake of meat and processed foods ( 1 – 3 ). Higher levels of adherence to the Mediterranean diet are associated with reduced risk of inadequate nutrient intake, indicating that the diet provides a variety of essential nutrients ( 4 ). However, for decades many Mediterranean countries have been drifting away from this traditional Mediterranean dietary pattern with increased intake of animal products and ultra-processed foods and decreased consumption of plant-based foods ( 5 , 6 ).

This change in diet has health implications for the Mediterranean population because adherence to the Mediterranean diet is associated with numerous health benefits, including reduced risk of several major chronic diseases. There is consistent evidence that better adherence to the Mediterranean diet is associated with clinically meaningful reductions in rates of coronary heart disease, ischemic stroke, and total cardiovascular disease (CVD) ( 7 ). A 2-point increase in adherence to the Mediterranean diet is associated with an 8–9% reduction in overall mortality and a 10% reduction in risk of CVD ( 8 , 9 ). Higher adherence to a Mediterranean diet is also associated with a 19–23% reduction in the risk of developing diabetes ( 10 , 11 ) and a reduced incidence of cancers ( 8 , 9 , 12 ). Adherence to a Mediterranean diet may also reduce the risk of neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease ( 8 , 13 ).

Because the Mediterranean diet describes a general dietary pattern of a large and diverse region, which includes 22 countries, there is no single version of the Mediterranean diet. It varies with geography and historical time, and it is adapted by each specific geographic area and population ( 14 ). As the food systems and availability in a region change, dietary patterns may change to reflect this. The availability and consumption of non-traditional foods have been increasing in the Mediterranean region, and one potential way of shifting the dietary pattern back to a more healthful nutrient profile is to encourage intake of fruits and vegetables regardless of whether they are traditionally consumed in the Mediterranean region. Incorporating non-traditional foods such as avocados into the Mediterranean dietary pattern could provide greater flexibility in suitable food choices, and provide greater adaptability for populations outside of the Mediterranean region.

Nutritional Attributes of Avocados

Avocados ( Persea americana ) are nutrient-dense and botanically considered a fruit, but they are not traditionally included in the Mediterranean diet. Avocados may be pear-shaped, egg-shaped, or spherical, and they consist of a single large seed surrounded by a creamy, smooth textured, edible fruit and are covered by a thick, bumpy skin that turns purplish black when ripe. The Mediterranean diet traditionally includes high consumption of fruits and vegetables, and the World Health Organization (WHO) recommends eating at least 400 g, or five portions, of fruit and vegetables per day to reduce the risk of non-communicable diseases and to ensure adequate intake of dietary fiber ( 15 ). A serving of avocado (50 g or ~1/3 of a medium-sized fruit) contains 3.4 g dietary fiber (11% DV), 44.5 μg folate (10% DV), 0.73 mg pantothenic acid (15% DV), 85 μg copper (10% DV), and 10.5 μg vitamin K (10% DV) ( 16 ). Avocados have a low energy density of 1.6 kcals/g or 80 kcals/serving. One serving of avocado contains 5 g monounsaturated fatty acid (MUFA) and 1 g polyunsaturated fatty acid (PUFA), with the predominant fatty acid being oleic acid at 4.53 g/serving ( 16 ). Avocados also contain numerous bioactive phytonutrients that may impart health benefits ( 17 – 21 ).

Table 1 shows the nutrient composition of avocados compared to other commonly consumed foods which are part of the Mediterranean diet. Both avocados and olive oil are rich in oleic acid, and they have a similar ratio of unsaturated to saturated fat (6:1) while avocados simultaneously provide other important nutrients. Like avocados, nuts are also a source of fiber, potassium, and folate, but they have a high energy density with walnuts providing 185 kcal/serving which is two times higher than the amount of energy provided by a serving of avocado.

Table 1 . Nutrient composition of avocados compared to commonly consumed foods in the Mediterranean diet.

Health Benefits of Avocados

Population data demonstrate the health benefits of consuming more fruits and vegetables. A meta-analysis of 95 unique cohort studies found inverse associations between high intakes of fruits and vegetables and risk of CVD, certain cancers, and all-cause mortality ( 22 ). Fruit intake has also been shown to be associated with reductions in body weight, waist circumference, and risk for obesity ( 23 ). Evidence from randomized controlled trials suggests that increasing the consumption of fruits and vegetables has favorable effects on CVD biomarkers such as blood pressure and lipids ( 24 ). Avocados and olives are unique among fruits in that they contain high levels of fat, specifically MUFA. Numerous organizations, including the WHO, American Heart Association, and 2015–2020 Dietary Guidelines for Americans, recommend replacing saturated and trans fats with MUFA and PUFA to reduce the risk of CVD ( 25 – 27 ). Substituting saturated fats with unsaturated fats is also associated with a significant reduction in total mortality ( 28 ). Previous clinical studies provide evidence suggesting that eating avocados may yield health benefits ( 29 ), and here we provide an update on recent research in the area.

Nutrient Status

Avocado consumption is associated with better diet quality and increased intake of important nutrients. Analysis of data from the National Health and Nutrition Examination Survey (NHANES) revealed that among U.S. adults, avocado consumption was associated with better diet quality, including significantly higher intake of fruits, and vegetables, and a lower intake of added sugars ( 30 ). Avocado consumers also had significantly higher intakes of dietary fiber, vitamins E and K, magnesium, and potassium. The average avocado intake by consumers was 70 g/day, which is equivalent to about half of a fruit.

Avocados can also increase the absorption of lipid-soluble bioactive phytonutrients such as carotenoids. Adding avocado to salsa enhances the absorption of lycopene and β-carotene, while adding avocado to a salad increases absorption of α-carotene, β-carotene, and lutein ( 31 ). Adding avocado to a meal increased the absorption of β-carotene from both tomato sauce and raw carrots, and increased the efficiency of bioconversion (5–13 fold increase) of β-carotene to vitamin A ( 32 ). Thi suggests that consuming a lipid-rich food with vegetables high in β-carotene may be especially important for people with low vitamin A status ( 32 ).

Avocado consumption enhances the absorption of the carotenoids lutein and zeaxanthin, which accumulate in the eyes and brain. Lutein and zeaxanthin accumulate in the macula of the retina and retinal lutein concentrations (macular pigment density) are correlated to brain lutein concentrations ( 33 ). In a randomized controlled trial, eating one avocado per day for 6 months increased serum lutein by 0.93 nmol/L and increased macular pigment density by 0.101 OD compared with the control group which consumed potatoes or chickpeas ( 34 ). Interestingly, previous work from the same authors, found that lutein supplementation of 12 mg/day for 4 months increased serum lutein by 0.22 nmol/L and macular pigment density by 0.041 OD ( 35 ). Therefore, even though avocados contain a small fraction of the amount of lutein found in the supplement, they were far more effective at increasing serum lutein and macular pigment density. This is likely because avocados contain MUFA, which enhance the absorption of carotenoids, and previous data has shown that consuming avocados modulates lipoproteins that are responsible for carotenoid transport ( 36 ). Eating avocados may also contribute to brain and eye health since macular pigment density is related to cognitive function in adults ( 33 ). Specifically, in the 6-months intervention trial participants consumed ~500 μg of lutein daily from avocado, which led to increases in serum lutein and macular pigment density ( 34 ). In the avocado group, these changes in macular pigment density correlated with improvements in spatial working memory and efficiency in approaching a problem. These results align with previous research showing that higher lutein status is related to better cognitive performance ( 33 ).

Cardiometabolic Health

CVD is the leading cause of morbidity and mortality worldwide, but the risk of CVD can be meaningfully reduced by consuming a healthy diet that emphasizes fruits, vegetables, legumes, nuts, whole grains, and fish ( 26 ). Eating avocado as part of a healthy diet has been shown to modify some cardiometabolic risk markers such as lipid profile ( 29 ). In an analysis of NHANES data, avocado consumers had significantly higher high-density lipoprotein cholesterol (HDL-C) levels and a 50% lower odds ratio for metabolic syndrome ( 30 ). Potentially beneficial effects of avocados on lipid profile have also been seen in meta-analyses. Mahmassani et al. conducted a meta-analysis of 18 studies examining avocado consumption and cardiovascular risk factors, and they found that avocado intake was associated with increased HDL-C ( 37 ). A previous meta-analysis by Peou et al. included 10 studies assessing avocado intake and plasma lipoproteins, and found that avocado intake was associated with reduced total cholesterol, low-density lipoprotein cholesterol (LDL-C), and triglycerides ( 38 ). The difference in findings may be due to variations in data analyses. Mahmassani et al. evaluated the net change in serum lipids (change in the avocado arm—change in the control arm) whereas Peou et al. only compared changes in the avocado arms without accounting for changes in the control arms. Though the methods and findings differ somewhat, these studies indicate that avocado consumption likely alters the lipid profile.

Randomized controlled trials have also demonstrated that eating avocado can improve lipid profiles. In a randomized, crossover, controlled feeding study, consuming a moderate-fat diet containing one avocado a day for 5 weeks reduced LDL-C and non-HDL-C more than a moderate-fat diet or a low-fat diet ( 36 ). Moreover, only the avocado-containing diet significantly reduced the number of small dense LDL-C particles, oxidized LDL-C, and the ratio of LDL-C/HDL-C ( 39 ). Another randomized, crossover, controlled feeding study found that consuming a whole avocado (136 g), as part of a breakfast meal, lowered concentrations of triglyceride-rich lipoproteins, and increased larger HDL-C particles, compared to an energy-matched, higher-carbohydrate meal ( 40 ). Eating either a whole or a half avocado as part of breakfast also significantly reduced postprandial glycemic and insulinemic responses compared to a control meal. Similarly, in a randomized, crossover study, Wien et al. compared a control meal to a lunch that included avocado (isocaloric) or avocado added to the lunch (+112 kcal) on insulin and glucose levels ( 41 ). The insulin area under the curve (AUC) was lowest when avocado was exchanged for other components of the meal (isocaloric). These studies suggest that avocado consumption may augment cardiometabolic risk markers.

Weight Management

Obesity rates have been increasing worldwide for several decades, and a healthy dietary pattern is an important component of weight loss and weight management. In the U.S. population, avocado consumers have lower body weight, body mass index (BMI), and waist circumference compared with non-consumers ( 30 ). Avocado consumers are also less likely to be overweight or obese and less likely to have an elevated waist circumference compared with non-consumers. Specifically, analysis of the 2001–2012 NHANES dataset reported avocado consumers were 33% less likely to be overweight or obese and 32% less likely to have an elevated waist circumference compared to non-consumers ( 42 ). Moreover, on average, avocado consumers weighed 3.4 kg less, had a mean BMI of 1 unit less, and had a waist circumference 3.0 cm smaller compared to non-consumers. A longitudinal study of ~55,400 7th-day Adventists in the U.S. in Canada found that avocado consumers gained significantly less weight over time (4–11 years follow-up) than non-consumers ( 43 ).

One possible explanation for these findings is that including avocados may increase satiety and reduced hunger when included in meals. A randomized, controlled clinical trial demonstrated that participants could eat one whole avocado daily without derailing their weight loss efforts ( 44 ). Study participants who ate an avocado daily as part of a hypocaloric diet maintained a similar feeling of satiety throughout the study compared to a reduction in satiety reported by participants on the control diet. Wien et al. found participants reported increased meal satisfaction and reduced desire to eat following a lunch that added half an avocado compared to eating the meal with no avocado ( 41 ). In the study by Zhu et al. participants reported increased satisfaction associated with eating a breakfast meal which included a half or a whole fresh avocado, compared to an isocaloric, high-carbohydrate control meal ( 45 ). Hunger was also significantly suppressed by the whole avocado-containing meal. These studies only examined subjective measures of appetite, and further research would be needed to determine if there are corresponding changes in caloric intake. The body of evidence thus far suggests that avocados could be a good addition to the Mediterranean diet pattern as there is evidence suggestive of health benefits and no evidence of harm.

Observational Datasets to Assess the Role of Avocado, as Part of a Mediterranean Diet, on Health

There are several challenges of using existing observational data to assess the impact of an avocado-containing dietary pattern on health. One challenge is that avocado intake is poorly captured in existing datasets. Countries that historically have consumed the most avocados (Mexico and other Latin American countries) do not have adequately funded federal programs to capture the information. In the U.S., the NHANES dataset uses two 24-h dietary recalls, which fail to adequately capture the intake of foods that are sporadically consumed, like avocados. Other large datasets that capture a range of avocado intakes, such as the Adventist Health Study-2 or the Hispanic Community Health Study/Study of Latinos, do not represent the general demographics of the U.S. population. Another challenge is potential confounding with other commonly co-consumed foods. Avocados are most commonly consumed as guacamole, which may be co-consumed with a dipper such as tortilla chips or vegetable sticks. Avocados are also frequently used in salads or as an add-on to sandwiches. The co-consumption of avocados with other foods and changes in the preferred methods of consumption over time may make data analysis challenging. A final challenge is that a biomarker of intake does not exist for avocados, so there is currently no objective way to validate self-reported consumption; however, given that avocado consumption is associated with better diet quality and avocados also have potential health benefits, adding avocados to clinical food assessments, and diet scores, may improve disease/mortality predictions at the population level.

Model of Avocado Exchanges in a Mediterranean Dietary Pattern

To date, no observational or intervention study has investigated the role of avocados within a Mediterranean dietary pattern. A simple dietary food pattern was developed ( Table 2 ) which represents a typical 3-days Mediterranean diet with or without avocado. In this isocaloric model, avocado was exchanged for fruit, vegetable, oil, nuts, dairy, and legumes in reasonable culinary swaps. In this model, the avocado-inclusive Mediterranean diet provided slightly less sugar (−7 g/d), sodium (−225 g/d), vitamin D (3 IU/d), and calcium (−132 mg/d) with an increase in fiber (+10 g/d), plant sterols (+114 mg beta-sitosterol/d), folate (+124 mg/d), and potassium (+552 mg/d). Nutrient intake would differ in other models which include varying amounts of avocado. Also, nutrient and food group intake would differ with other reasonable culinary exchanges in the food pattern. As an example, a diced avocado relish can be used on top of chicken or fish, or avocados can easily be added to salads and soups. Avocados can replace some spreads and baking ingredients to increase nutrient density and improve the ratio of unsaturated to saturated fatty acids.

Table 2 . Comparison of a 3-days typical Mediterranean dietary pattern compared to a typical Mediterranean dietary pattern that includes one avocado a day.

Production and Consumption of Avocados

While avocados are a healthy and nutritious fruit, they are also well-suited for incorporation into the Mediterranean diet because production and consumption of avocados are increasing in the region. Although production of avocados in the Mediterranean region has historically been low, avocado trees thrive in a Mediterranean climate. Spain has the highest production in the Mediterranean region with ~67,000 tons produced in 2017 compared to 36,000 tons produced in 2014 ( 46 – 48 ).

Avocado consumption is increasing in many countries around the world with approximately half of all avocados consumed in the United States, a third consumed in the European Union, and 20% consumed in other world markets ( 47 ). In areas where avocado intake is increasing rapidly, such as the Mediterranean, fruit needs to be imported from outside the region. Although per capita consumption is still quite low in the Mediterranean region, avocado intake has radically increased in the region over the last 5 years. Between 2013 and 2018, per capita consumption of avocados increased 267% in Spain from 0.3 to 1.1 kg, increased 300% in Italy from 0.1 to 0.4 kg, increased 200% in Greece from 0.2 to 0.6 kg, and increased 50% in France from 1.2 to 1.8 kg ( 49 ). Overall, per capita consumption in the European Union increased 150% from 0.4 to 1.0 kg ( 49 ). In comparison, per capita consumption in the United States increased 28% over the same time period from 2.5 to 3.2 kg ( 50 ).

Finding easy and familiar ways to incorporate avocado into traditional Mediterranean dishes may ease the adoption of the fruit. Incorporating avocados into the Mediterranean diet may also make the dietary pattern more adaptable to populations outside of the Mediterranean region, including those more familiar with consuming avocados.

Conclusions

Avocados are a healthy and nutritious fruit which are well-suited for growth in the Mediterranean region. Consumption is increasing across the Mediterranean region and eating avocados may help people preserve a nutrient profile that is similar to the traditional Mediterranean dietary pattern. Additionally, incorporation of non-traditional fruits such as the avocado may make the dietary pattern more adaptable to populations outside of the Mediterranean region and increase ease of adherence by incorporating fruits that are already familiar. Research is needed to address these hypotheses. Lastly, adding avocados to clinical food assessments and diet scores may improve disease/mortality predictions at the population level.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Author Contributions

NF conceived of the work, contributed to the writing, and offered critical comments. AL wrote the first draft of the manuscript and provided critital revisions to the content. All authors read and approved the final manuscript.

Supported by the Hass Avocado Board.

Conflict of Interest

NF is an employee of the Hass Avocado Board. AL received payment from the Hass Avocado board for writing and editorial services.

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49. Fruit Logistica, Messe Berlin GmbH. European Statistics Handbook. Berlin, Germany: Fruit Logistica, Messe Berlin GmbH (2019).

50. United States Department of Agriculture Economic Research Service. Fruit and Tree Nut Yearbook Tables. Available online at: https://www.ers.usda.gov/data-products/fruit-and-tree-nut-data/fruit-and-tree-nut-yearbook-tables/#General (accessed January 13, 2020).

Keywords: avocado, Persea americana , Mediterranean, dietary pattern, plant-based, oleic acid

Citation: Ford NA and Liu AG (2020) The Forgotten Fruit: A Case for Consuming Avocado Within the Traditional Mediterranean Diet. Front. Nutr. 7:78. doi: 10.3389/fnut.2020.00078

Received: 15 January 2020; Accepted: 04 May 2020; Published: 29 May 2020.

Reviewed by:

Copyright © 2020 Ford and Liu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Nikki A. Ford, nikki@hassavocadoboard.com

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Avocado Seed: A Comparative Study of Antioxidant Content and Capacity in Protecting Oil Models from Oxidation

Francisco j. segovia.

1 Chemical Engineering Department, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona, Spain; moc.liamg@jfaivoges (F.J.S.); moc.liamg@tcatnocimehc (G.I.H.); moc.liamg@etnasallivanailuj (J.V.)

Gádor Indra Hidalgo

Juliana villasante, xavier ramis.

2 Heat Engines Department, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona, Spain; ude.cpu.tmm@simar

María Pilar Almajano

Increasingly, consumers want products containing little or no synthetic compounds. Avocado seeds, which are a residue of the food industry, could be used to obtain extracts with high antioxidant power. In the present study, the most popular radical scavenging methods are presented, establishing a comparison between them, besides working with two different extractions: pure methanol and ethanol–water (50:50 v/v ). The radical scavenging assay methods ORAC and ABTS were performed, as well as a novel method: the reaction to methoxy radical, as determined by electron paramagnetic resonance (EPR). Peroxide value and thiobarbituric acid reactive compounds (TBARs) were used to monitor the oxidation of avocado seed oil, as well as the power of the avocado seed extract (ASE) to delay oil oxidation by oxidation induction time (OIT) and measured by differential scanning calorimetry (DSC). Radical scavenging methods have values between 1310–263 µmol TE/g of mass dissolved for ORAC and ABTS, respectively. The individual contribution of each of the compounds present in the extract was analyzed. The sum of all of them contributed up to 84% of the total radical scavenging activity. The concentration of 0.75% ASE causes a delay in the oxidation that is close to 80%, as measured by OIT. This implies that avocado seed residue may have a use as a natural antioxidant source, providing added value to organic waste.

1. Introduction

Polyphenols are widely recognized to have antioxidant properties [ 1 ]. They are very useful in food preservation to extend the shelf life of products, since they protect against microorganisms and prevent lipid peroxidation due to the attack of free radicals [ 2 , 3 ]. In addition, they protect against direct or indirect oxidation caused by metal cations [ 4 ]. These cations stimulate the creation of reactive oxygen species (ROS), which are harmful to human health. Previous to human studies, the determination of the radical scavenging (ORAC, ABTS, and DPPH methods) are commonly applied for the analysis of many matrices as vegetables [ 5 , 6 , 7 , 8 ], juice fruits [ 9 , 10 ], and vegetables oils [ 11 , 12 ].

The food industry elaborates many by-products and waste due to its normal fabrication of goods. These types of residues have a significant environmental impact due to the great organic charge they contain, as well as their associated handling, transport, and storage costs, among others [ 13 , 14 ]. Therefore, more alternative uses for these wastes are sought, as, for instance, animal feed and fertilizers. Some examples of these [ 15 , 16 , 17 ] are found in the fruit juice industry, where a large amount of oil, skin, and seeds from oranges, apples, and peaches are wasted with a high content of polyphenols. Also, the residues from wine production include phenolic compounds [ 18 ]. Giuffrè showed that the amounts of phenolic compounds that were contained in grape skin changed throughout the fruit-ripening process [ 19 ]. Other studies have focused on the shells of nuts, in which large amounts of tannins are found. There is evidence that the skin may even have a greater amount of polyphenols than the kernel itself [ 20 ]. These by-products are used in the chemistry, cosmetic, and pharmaceutical industries as natural additives [ 13 ].

The avocado ( Persea americana Mill.) is native to Central America. Mexico is the largest producer of avocados worldwide [ 21 ], and the worldwide production exceeds three million tons. In the industry, the pulp is used, while the skin and the seeds are discarded. These residues are rich in polyphenols with antioxidant and antimicrobial power [ 22 ]. Condensed tannins, phenolic acids, and flavonoids were the most representative groups in avocado seed. Among the polyphenols, (+)-catechin, (−)-epicatechin, and 3-leucoanthocyanidins are found [ 23 ]. Recent studies demonstrated that the seed of this fruit presents anti-inflammatory and anti-carcinogenic properties [ 24 ].

It has also been observed that the ASE presents acetogenin, with antimicrobial effect. These properties are stable in complex food systems [ 25 ], being useful in preventing the oxidation of model food systems such as emulsions of sunflower oil in water (10% oil) or meat burgers. They have been shown to be effective in preventing oxidation and microbial growth [ 26 ]. In both cases, it has been found that they can slow down oxidation over 60% [ 27 ].

The goal of this work is wide: (a) to compare different traditional methods of radical scavenging, including the EPR methodology with the real-methoxy radical, (b) to analyze the contribution of each of the components present in the residue, and (c) to compare different techniques where the oxidation of sunflower oil is forced, including the OIT (oxidation induction time).

Avocado seed extract is effective as a natural antioxidant, showing protection against oxidation when added to sunflower oil as a food model. The main antiradical activity is due to several antioxidant molecules such as polyphenols and flavonoids.

2. Results and Discussion

2.1.total polyphenol content (tpc) and radical scavenging activity.

There are various authors working with different extracts from avocado seeds. Table 1 shows the conditions of extraction and the results obtained. The conversion to the same units was done to enable easy comparisons. There is a large scatter in the results, which is difficult to justify. On the one hand, the highest value obtained is in the extraction performed with methanol/water (75:25) by Pahua Ramos [ 28 ], while the lower value with the same kind of avocado ( Persea americana Mill. var. Hass) is obtained in the extraction with methanol/water 80:20 at 60 °C, which is 30 times lower than the value obtained by Kosinska [ 29 ]. On the other hand, López worked with Persea schiedeana, a different species from the same Genus than the avocado, and found lower values [ 30 ]. In the present study, the TPC that was found was 30.98 ± 0.68 mg gallic acid equivalents (GAE)/g DW with ethanol/water 50:50 extraction at 4 °C overnight. It is similar to the amount described by Rodríguez-Carpena [ 31 ] with methanol/water 70:30. In this research, ethanol:water (50:50) was selected due to its Generally Recognized As Safe (GRAS) nature versus methanol.

Different radical scavenging values found in the bibliography.

α [µmol TE/g DW]; β [mmol TE/g FW]; γ IC 50 [µg/mL]; δ [µmol Fe 2+ /g DW]; 1 var. Hass; 2 var. Fuerte.

In Table 1 , four authors reported the results for the ORAC, and the dispersion was similar. Results range from above 600 µmol TE/g DW [ 27 ] when extracting with ethanol down to those values close to 100 µmol TE/g DW [ 35 ] when using methanol. The value obtained in the present study was the highest, which was more than 1300 µmol TE/g DW. No correlation between the two values (ORAC/TPC) was found for any of the displayed articles.

Using the ABTS as a radical, the dispersion is also remarkable. The highest value [ 26 ] is greater by a factor of almost 30 times to the one obtained for the different species, Persea schiedeana [ 30 ]. The value obtained in this study is in the lower range for Persea americana (263 µmol TE/g DW). Apparently, here, the use of ethanol as the extracting solvent yields higher values of antioxidant capacity with ABTS. Regarding DPPH, high variability was also reported amongst studies, concluding that the extraction conditions, the sample origin, and the methodology for radical scavenging determination affect the results obtained to a great extent.

In the present study, the most popular radical scavenging methods are presented, establishing a comparison between them, besides working with two different extractions. On the other hand, a novel method is incorporated, the reaction to methoxy radical, as determined by EPR. Table 2 shows the results with different units. The EPR analyzes a competitive reaction to DMPO [ 36 , 37 , 38 ], which acts also, scavenging the radicals generated “in situ”.

Radical scavenging values of avocado seed extract (ASE) obtained with pure methanol and ethanol/water.

1 g ferulic acid equivalents (FAE)/g DW.

Table 2 shows the radical scavenging values obtained with pure methanol and ethanol/water (50:50). There is not a value for the EPR with ethanol/water, because there is an interference with the water in the determination. The standard used is ferulic acid for a similar reason, in order to avoid interferences and facilitate the solubility in the adequate concentration.

For the EPR determination, the value for the ASE is lower than the other values obtained previously by Azman et al. in white tea (1.33 ± 0.3 FAE/g white tea extract) [ 38 ].

In plant extracts, products are many individual compounds contributing to the overall antioxidant activity. While we would highlight the interactions between them and the synergistic effect, it is also important to consider the individual contribution to the antioxidant activity exerted by the compounds separately. To do this, after the separation by HPLC with a gradient polarity (as it is contained in materials and methods), the injection of the ABTS radical generated “in situ” was performed. Therefore, the negative peak corresponds to the radical scavenging activity, and the higher negative area corresponds to the higher antiradical activity.

In direct chromatogram, prior to the injection of ABTS, (+)-catechin, (−)-epicatechin, and an isomer of chlorogenic acid have been identified at concentrations of 20.10 mg/L extract, 27.89 mg/L extract, and 51.59 mg/L extract, respectively. In addition, there are three peaks belonging to the family of flavonoids. Rodríguez-Carpena [ 26 ] and Kosinska [ 29 ] also found these compounds in amounts of 57.5 µg/g DW and 282.7 mg/100 g DW. Figure 1 shows the HPLC performed to ASE. The chlorogenic acid is the polyphenol that is found in highest quantity. This acid is found in many natural plant extracts, and its influence on the antioxidant capacity and captured hydroxyl radicals has been amply demonstrated [ 39 ], because it contains a catechol group that makes it especially effective for capturing free radicals [ 40 , 41 ].

An external file that holds a picture, illustration, etc.
Object name is molecules-23-02421-g001.jpg

HPLC chromatogram of the extract of ASE. Chlorogenic acid (1), (+)-Catechin (2), (−)-Epicatechin (3).

Figure 1 also includes the “negative” peaks, which are in the chromatogram having antiradical activity. This method has already been described in earlier publications, and is an effective, fast, and sensitive analysis for individual components [ 42 , 43 , 44 ]. Table 3 lists the values quantified with gallic acid.

ASE composition and antioxidant capacity of their compounds.

* belongs to the family of procyanidin; ** belongs to the family of catechins.

The first flavonoid (RT 15.36 min) with the chlorogenic acid and the (−)-epicatechin are those that provide the largest percentage of radical scavenging activity. Below are (+)-catechin and other flavonoids. The sum of the percentages of the individual peaks provides over 84% of the radical scavenging activity with the ABTS radical. The difference up to 100% can be due to the synergistic effect between the different compounds or also due to other compounds that are not detectable with the separation by this HPLC method. In any case, the percentage of individual peaks is very high, and justifies the major part of the antiradical activity. All of them are well-known antioxidants that are present in coffee, tea, and other plant extracts [ 45 , 46 , 47 , 48 ], which have been successfully used in preventing lipid oxidation in foods [ 38 , 49 , 50 ].

2.2. Protective Effect of ASE in Sunflower Oil Fatty Acid Mixture

To evaluate the antioxidant activity in a model system (sunflower oil stripped from its natural antioxidants), different percentages of ASE were added. The control sample was prepared without antioxidant, and the positive controls were prepared with synthetic antioxidant (BHT). These samples were subjected to two types of analysis. The evolution of primary oxidation was monitored by peroxide value (PV) and secondary oxidation by thiobarbituric acid reactive compounds (TBARs). The first forced oxidation was carried out at moderate temperature (23 days at 35 °C). The second method is a much forced oxidation, which determines the OIT (oxidation induction time) by DSC (differential scanning calorimetry) at 100 °C and 10 L/min of air.

2.2.1. Primary Oxidation of Sunflower Oil by Peroxide Value

The evolution of PV results over time in moderate oxidation (35 °C) is set out in Figure 2 . In addition, Table 4 lists the induction time of each and the slope or rate of oxidation at the starting time. Vaidya showed similar results working with walnut oil and grape seed oil [ 51 ]. Three different concentrations (0.25%, 0.50% and 0.75%) of ASE have been studied. The effect on the antioxidant activity is proportional to the concentration. Furthermore, in this range of concentrations, it has not reached a concentration that can have pro-oxidant effect.

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Object name is molecules-23-02421-g002.jpg

Changes in the peroxide value (PV) of a sunflower oil fatty acid mixture at 35 °C.

Parameters of the different methods to calculate the antioxidant activity.

1 Data from PV graphics; 2 Data from differential scanning calorimetry (DSC) graphics; 3 Hydroperoxide value at 10 days of experiment; 4 Thiobarbituric acid reactive compounds (TBARs) value at 15 days of experiment. a,b,c,d,e Means within each column with different superscripts are significantly different ( p < 0.05). IT: induction time; OIT: oxidation induction time.

For the concentration of 0.75% of ASE, the maximum PV is reached at t = 500 h, which compared to the same value for the control (t = 100 h), implies a reduction of oxidation, with a more than five times increased shelf life. The results are similar to those obtained with 0.01% BHA. The lower concentration of ASE values (0.25%) also has a protective effect, although lower (two times delayed with respect to the control sample). Abdelazim [ 52 ] worked with sesame extract and found a similar delay of the oxidation.

Other natural sources of antioxidants from food have been previously compared with synthetic preservatives. Sesame cake extract at a concentration of 200 mg/L has stabilization efficiency comparable to commonly-used synthetic antioxidants BHT and BHA at their legal limit, but has lower efficiency than that of the synthetic antioxidant TBHQ [ 52 ]. Also, it has been successfully worked with pure compounds as chlorogenic acid and caffeic acid in the presence of mixtures triacylglycerols, and they found a similar delay in the samples oxidation, where at 2.8 × 10 −4 M, both acids show equal effectiveness and strength. At concentrations above 10 × 10 −4 M, caffeic acid appears as a much more effective and stronger inhibitor [ 45 ].

The control has a negligible induction time ( Table 4 ). All of the other samples have an induction time that allows the calculation of PV 10 . This is a distinguishing feature to previous studies [ 53 ], demonstrating the high antioxidant activity of ASE at the concentrations used.

2.2.2. Secondary Oxidation of Sunflower Oil by TBARs

Figure 3 shows the evolution of TBARs over time. The first values (at the beginning of the oxidation, before the hydroperoxides have been formed) are negligible, but the increase starts at the eighth day which coincides with a significant increase in the compounds obtained by the primary oxidation. The sample with 0.25% of ASE has a delay of 43% over the control one, while in the sample with 0.75%, the percentage of delay is 77%.

An external file that holds a picture, illustration, etc.
Object name is molecules-23-02421-g003.jpg

Changes in the TBARs value of sunflower oil fatty acid mixture at 35 °C in the dark.

The OIT method allows the obtainment of comparable results in hours versus days of the PV and TBARs. It is to perform an accelerated oxidation with oxygen in the conditions studied and measured by DSC. They are shown in Figure 4 and Table 4 . It is not the first time that this method has been used to calculate the oxidation. For example, it was used in a study with cocoa butter [ 54 ] with added extracts of pulp obtained from Barbados cherry, mango, and guava, which increased the oxidative stability of soybean oil at certain concentrations [ 55 ]. It was also used to determine the time that it takes to oxidize a fat, and consequently the protective effect that the extract or antioxidant that was added had in other oils such as cottonseed, canola, and sunflower [ 56 ], with good results. The considerable reduction of time (less than 6 h per sample) allows it to be a quick and reliable method for the food industry, to assess the protective effect of antioxidants or, where applicable, to find potential synergies that may decrease the final amount of a particular synthetic antioxidant.

An external file that holds a picture, illustration, etc.
Object name is molecules-23-02421-g004.jpg

Isothermal analysis to determinate OIT value for sunflower oil fatty acid mixture.

In Figure 4 , the control displays an immediate oxidation in the conditions applied, where the OIT is very difficult to appreciate at this scale. No significant differences were found between the two lower concentrations of ASE used. Both have an OIT somewhat higher 41–43 min, representing more than 45% of the protection against the forced oxidation compared to the control. Nevertheless, in the higher concentration (0.75%), the OIT has a value close to 53 min, which is above the value achieved with the lower concentration of BHA (0.01%), and an increase of 85% in the stability of the fatty acid mixture analyzed ( Table 4 ). As in other studies where they have applied natural extracts to prevent the oxidation of fish oils [ 57 ], sunflower oil that is high in oleic acid and castor oil natural extracts prevents oxidation; [ 58 ] the ASE possesses antioxidant activity due to the influence of the components found in the extract.

Future research could be focused on the application of ASE into foods such as meat, fish, margarine, etc., and quantify the increase in the shelf life of those foods, as well as asses the acceptability of the products in the market by sensory analysis.

3. Materials and Methods

3.1. sample and extracts preparation.

Refined sunflower oil was purchased from a local retail outlet. Sunflower oil was passed through alumina as described by Skowyra [ 59 ] in order to remove naturally present tocopherols. The avocado ( Persea americana Mill. var. Hass) was obtained from a local market in Barcelona (Spain), with the adequate ripeness for consumption; the seeds were separated from other edible parts. First, 25 seeds were ground into a powder by using a Moulinex mill (A5052HF, Moulinex, Lyon, France). The particle size was standardized with a number 40 mesh sieve. It was homogenized and frozen at −80 °C for lyophilization. Finally, the powder was stored in an amber bottle in a desiccator until use.

Extraction was carried out in amber bottles. Lyophilized powder (0.25 g) was blended with 25 mL of solvent (methanol/water 50:50). This mixture was placed under stirring in a refrigerator at 4 °C overnight, centrifuged (Orto Alresa, Madrid, Spain) at 2500 rpm for 10 min, and the supernatant was separated as extract. Ethanol was eliminated by rotoevaporation, and the extract was freeze-dried and stored until used for analysis. To obtain the sample for EPR, pure methanol was used.

3.2. Material and Reagents

Trolox (6-hydroxy-2,5,8-tetramethylchroman-2-carboxylic acid), ethanol, fluorescein, AAPH, BHA, and 2-thiobarbituric acid, Chlorogenic acid, (+)-Catechin, and (-)-Epicatechin were purchased from Sigma-Aldrich Company Ltd. (Gillingham, UK). Folin-Ciocalteu reagent, sodium carbonate and 1,6-diaminohexane were supplied by Merck (Darmstadt, Germany). Iron(II) sulfate (FeSO 4 ), DMPO, H 2 O 2 , MeOH, trichloroacetic acid, and hydrochloric acid were acquired from Panreac Química S.L.U. (Barcelona, Spain). All of the compounds were of reagent grade.

3.3. Chemical Analysis

3.3.1. total polyphenol content (tpc).

TPC was determined spectrophotometrically following the Folin–Ciocalteu colorimetric method [ 60 , 61 ]. A sample diluted 1:4 with milli-Q water was stirred in triplicate. The final concentration in each one of the 96-well plates that were used was: 7.7% v/v sample, 4% v/v Folin–Ciocalteu’s reagent, 4% saturated sodium carbonate solution, and 84.3% of milli-Q water, all mixed. The solution was allowed to react for 1 h in the dark, and the absorbance was measured at 765 nm using a Fluostar Omega (BMG Labtech, Ortenberg, Germany). The total phenolic content was expressed as mg gallic acid equivalents (GAE)/g dry weight.

3.3.2. Radical Scavenging Activity

ORAC [ 27 ], FRAP [ 62 ], and TEAC [ 63 ] methods were used. The results are expressed as µmol Trolox equivalents (TE)/g of dry weight or µmol ferulic acid equivalents/g of dry weight.

3.3.3. Determination of Methoxy Radical Scavenging Activity by EPR

The method was reported by Azman [ 38 ]. The extract was prepared in deoxygenated MeOH. A spin-trapping reaction mixture that consisted of 100 μL of DMPO (35 mM), 50 μL of H 2 O 2 (10 mM), 50 μL of avocado methanol extract (0−8.13 g/L), or 50 μL of ferulic acid used as reference (0−20 g/L) or 50 μL of pure MeOH used as a control; and, finally, 50 μL of FeSO 4 (2 mM). The final solutions (250 μL) were passed through a narrow quartz tube (inside diameter = 2 mm) and introduced into the cavity of the EPR spectrometer. The spectrum was recorded 12 min after the addition of the FeSO 4 solution, when the radical adduct signal was the greatest.

X-band EPR spectra were recorded with a Bruker EMX-Plus 10/12 spectrometer (Bruker, Billerica, MA, USA) under the following conditions: microwave frequency, 9.876 GHz; microwave power, 30.27 mW; center field, 3522.7 G; sweep width, 100 G; receiver gain, 5.02 × 104; modulation frequency, 100 kHz; modulation amplitude, 1.86 G; time constant, 40.96 ms; and conversion time, 203.0 ms.

Each measurement was carried twice. The first derivative of the absorption signal was integrated in duplicate, resulting in it being directly proportional to the concentration of the remaining radical adducts values, when the competitive reactions of the methoxy radical with DMPO and the antioxidant were completed. Then, these values were compared with those obtained with ferulic acid, which was used as a standard.

3.3.4. High Performance Liquid Chromatography (HPLC)

Identification and quantification were performed using a Waters 2695 Separations Module (Meadows Instrumentation, Inc., Bristol, WI, USA) system with a photodiode array detector Waters 996 (Meadows Instrumentation, Inc.). A Kinetex 2.6-u C18 100A, (100 × 4.6 mm) column was used. Mobile phase was 0.1% acetic acid in water ( v / v ) (eluent A) and 0.1% acetic acid in acetonitrile (eluent B). The gradient used was: 0–2 min, isocratic gradient from 0% B; 2–40 min, linear gradient from 0–15% B; and a 40–50 min linear gradient from 0–15%. B. The flow rate was 0.8 mL/min. Detection wavelengths were 280 nm and 330 nm. The sample injection volume was 10 µL. The chromatographic peaks were confirmed by comparing their retention times and diode array spectra against those of their reference standards, and the chlorogenic acid was confirmed by MS HPLC-MS. Working standard solutions between 100–500 mg/L were injected into the HPLC to obtain the calibration curve plotting concentration (mg/L) versus area. Quantification was carried out from integrated peak areas of the samples using the corresponding standard graph.

For the analysis of the radical scavenging activity of each of the compounds by ABTS radical, a pump Merk-Hitachi HPLC gradient pump (Model L-6200) (Hitachi High Technologies America Inc., Schaumburg, IL, USA) was coupled with a 0.2 mL/min flow with an ABTS concentration of 0.03% ( w / v ). This allowed a perfect mixture thanks to the 3 m of tube where the flow could homogenize before reaching the detector.

The reading wavelength was 734 nm. The calibration curve to quantify the results was made with Gallic acid.

3.3.5. Determination of Primary Oxidation with Peroxide Value (PV) and Secondary Oxidation with TBARs Method

PV was determined by the ferric thiocyanate method [ 64 ] (after calibrating the procedure with a series of oxidized oil samples analyzed using the AOCS Official Method Cd 8-53 [ 65 ]). Data from the PV measurements were plotted against time.

The secondary oxidation of oil was determined by the concentration of thiobarbituric acid reactive substances (TBARs) using the method described by Gallego [ 66 ] with slight modifications. An amount of each sample was taken and the TBARs reagent (15% trichloroacetic acid, 0.375% thiobarbituric acid and hydrochloric acid 2.1%) was added in a ratio 1:5. Immediately, the samples were introduced in an ultrasonic bath (Prolabo brand equipment, Rue des Casernes, Sion) and immersed in a water bath pre-heated to 95 °C. Samples were centrifuged, and the absorbance of the supernatant was measured at λ = 531 nm. The results are expressed as mg MDA/kg of oil.

3.3.6. Oxidation Induction Time analysis (OIT-DSC)

Differential scanning calorimetry (DSC) experiments were performed with a DSC 820 from Mettler Toledo (Schwerzenbach, Switzerland) under isothermal conditions (100 °C) and with an airflow of 10 mL/min. The samples (5.00 ± 0.25 mg) were weighed into 40 µL aluminum DSC open crucible in order to allow the oil to be in contact with the oxygen stream. An empty crucible was used as reference.

4. Conclusions

The ASE is effective as a natural antioxidant. The main antiradical activity is due to polyphenols (+)-catechin, (−)-epicatechin, 3- O -caffeoylquinic acid (chlorogenic acid isomer), and three compounds of the flavonoid family. Its individual activity has been demonstrated by the HPLC post-column injection of ABTS, by different radical scavenging methods, including EPR, and also in the protection of sunflower oil oxidation devoid of its natural antioxidants. The degree of oxidation was followed by traditional methods (PV, TBARs), and also was determined by the OIT. Both are correlated, which states that it could be determined only by the OIT, saving both materials and time.

Abbreviations

TPC, Total Polyphenol Content; EPR, Electron Paramagnetic Resonance; ABTS, 2,2′azino-bis(3-ethyl-benzothiazoline-6-sulfonicacid); Trolox, (±)-6-hydroxy-2,5,7,8–tetramethylchromane-2-carboxylic acid; GAE, gallic acid equivalents; DW, dry weight; HPLC, High Performance Liquid Chromatography; TEAC, Trolox Equivalent Antioxidant Capacity; TE, Trolox Equivalent; ORAC, Oxygen Radical Absorbance Capacity; FRAP, Ferric Reducing Ability of Plasma; VP, Peroxide Value; TBARs, Thiobarbituric Acid Reactive substances; OIT, Oxidation Induction Time; DMPO, 5,5-dimethyl-pyrroline N-oxide; BHA, Butylated hydroxyanisole; BHT, Butylated hydroxytoluene; r.t., room temperature.

Author Contributions

Conceptualization, F.J.S. and M.P.A.; Validation, X.R. and M.P.A.; Formal Analysis, F.J.S., X.R.; Investigation, F.J.S., G.I.H. and J.V.; Resources, X.R. and M.P.A.; Writing-Original Draft Preparation, F.J.S.; Writing-Review & Editing, G.I.H., J.V.; Supervision, Project Administration and Funding Acquisition, M.P.A. All authors read and approved the final manuscript.

This research received no external funding.

Conflicts of Interest

The authors declare no conflict of interest.

Sample Availability: Samples of the compounds are not available from the authors.

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Published: 16 May 2024

The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch

Eman Ghoneim ORCID: orcid.org/0000-0003-3988-0335 1 ,
Timothy J. Ralph ORCID: orcid.org/0000-0002-4956-606X 2 ,
Suzanne Onstine 3 ,
Raghda El-Behaedi 4 ,
Gad El-Qady 5 ,
Amr S. Fahil 6 ,
Mahfooz Hafez 5 ,
Magdy Atya 5 ,
Mohamed Ebrahim ORCID: orcid.org/0000-0002-4068-5628 5 ,
Ashraf Khozym 5 &
Mohamed S. Fathy 6

Communications Earth & Environment volume 5 , Article number: 233 ( 2024 ) Cite this article

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Archaeology
Geomorphology
Hydrogeology
Sedimentology

The largest pyramid field in Egypt is clustered along a narrow desert strip, yet no convincing explanation as to why these pyramids are concentrated in this specific locality has been given so far. Here we use radar satellite imagery, in conjunction with geophysical data and deep soil coring, to investigate the subsurface structure and sedimentology in the Nile Valley next to these pyramids. We identify segments of a major extinct Nile branch, which we name The Ahramat Branch, running at the foothills of the Western Desert Plateau, where the majority of the pyramids lie. Many of the pyramids, dating to the Old and Middle Kingdoms, have causeways that lead to the branch and terminate with Valley Temples which may have acted as river harbors along it in the past. We suggest that The Ahramat Branch played a role in the monuments’ construction and that it was simultaneously active and used as a transportation waterway for workmen and building materials to the pyramids’ sites.

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Medieval demise of a Himalayan giant summit induced by mega-landslide

Quantitative assessment of the erosion and deposition effects of landslide-dam outburst flood, Eastern Himalaya

Introduction.

The landscape of the northern Nile Valley in Egypt, between Lisht in the south and the Giza Plateau in the north, was subject to a number of environmental and hydrological changes during the past few millennia 1 , 2 . In the Early Holocene (~12,000 years before present), the Sahara of North Africa transformed from a hyper-arid desert to a savannah-like environment, with large river systems and lake basins 3 , 4 due to an increase in global sea level at the end of the Last Glacial Maximum (LGM). The wet conditions of the Sahara provided a suitable habitat for people and wildlife, unlike in the Nile Valley, which was virtually inhospitable to humans because of the constantly higher river levels and swampy environment 5 . At this time, Nile River discharge was high, which is evident from the extensive deposition of organic-rich fluvial sediment in the Eastern Mediterranean basin 6 . Based on the interpretation of archeological material and pollen records, this period, known as the African Humid Period (AHP) (ca. 14,500–5000 years ago), was the most significant and persistent wet period from the early to mid-Holocene in the eastern Sahara region 7 , with an annual rainfall rate of 300–920 mm yr −1 8 . During this time the Nile would have had several secondary channels branching across the floodplain, similar to those described by early historians (e.g., Herodotus).

During the mid-Holocene (~10,000–6000 years ago), freshwater marshes were common within the Nile floodplain causing habitation to be more nucleated along the desert margins of the Nile Valley 9 . The desert margins provided a haven from the high Nile water. With the ending of the AHP and the beginning of the Late Holocene (~5500 years ago to present), rainfall greatly declined, and the region’s humid phase gradually came to an end with punctuated short wet episodes 10 . Due to increased aridity in the Sahara, more people moved out of the desert towards the Nile Valley and settled along the edge of the Nile floodplain. With the reduced precipitation, sedimentation increased in and around the Nile River channels causing the proximal floodplain to rise in height and adjacent marshland to decrease in the area 11 , 12 estimated the Nile flood levels to have ranged from 1 to 4 m above the baseline (~5000 BP). Inhabitants moved downhill to the Nile Valley and settled in the elevated areas on the floodplain, including the raised natural levees of the river and jeziras (islands). This was the beginning of the Old Kingdom Period (ca. 2686 BCE) and the time when early pyramid complexes, including the Step Pyramid of Djoser, were constructed at the margins of the floodplain. During this time the Nile discharge was still considerably higher than its present level. The high flow of the river, particularly during the short-wet intervals, enabled the Nile to maintain multiple branches, which meandered through its floodplain. Although the landscape of the Nile floodplain has greatly transformed due to river regulation associated with the construction of the Aswan High Dam in the 1960s, this region still retains some clear hydro-geomorphological traces of the abandoned river channels.

Since the beginning of the Pharaonic era, the Nile River has played a fundamental role in the rapid growth and expansion of the Egyptian civilization. Serving as their lifeline in a largely arid landscape, the Nile provided sustenance and functioned as the main water corridor that allowed for the transportation of goods and building materials. For this reason, most of the key cities and monuments were in close proximity to the banks of the Nile and its peripheral branches. Over time, however, the main course of the Nile River laterally migrated, and its peripheral branches silted up, leaving behind many ancient Egyptian sites distant from the present-day river course 9 , 13 , 14 , 15 . Yet, it is still unclear as to where exactly the ancient Nile courses were situated 16 , and whether different reaches of the Nile had single or multiple branches that were simultaneously active in the past. Given the lack of consensus amongst scholars regarding this subject, it is imperative to develop a comprehensive understanding of the Nile during the time of the ancient Egyptian civilization. Such a poor understanding of Nile River morphodynamics, particularly in the region that hosts the largest pyramid fields of Egypt, from Lisht to Giza, limits our understanding of how changes in the landscape influenced human activities and settlement patterns in this region, and significantly restricts our ability to understand the daily lives and stories of the ancient Egyptians.

Currently, much of the original surface of the ancient Nile floodplain is masked by either anthropogenic activity or broad silt and sand sheets. For this reason, singular approaches such as on-ground searches for the remains of hidden former Nile branches are both increasingly difficult and inauspicious. A number of studies have already been carried out in Egypt to locate segments of the ancient Nile course. For instance 9 , proposed that the axis of the Nile River ran far west of its modern course past ancient cities such as el-Ashmunein (Hermopolis) 13 . mapped the ancient hydrological landscape in the Luxor area and estimated both an eastward and westward Nile migration rate of 2–3 km per 1000 years. In the Nile Delta region 17 , detected several segments of buried Nile distributaries and elevated mounds using geoelectrical resistivity surveys. Similarly, a study by Bunbury and Lutley 14 identified a segment of an ancient Nile channel, about 5000 years old, near the ancient town of Memphis ( men-nefer ). More recently 15 , used cores taken around Memphis to reveal a section of a lateral ancient Nile branch that was dated to the Neolithic and Predynastic times (ca. 7000–5000 BCE). On the bank of this branch, Memphis, the first capital of unified Egypt, was founded in early Pharaonic times. Over the Dynastic period, this lateral branch then significantly migrated eastwards 15 . A study by Toonen et al. 18 , using borehole data and electrical resistivity tomography, further revealed a segment of an ancient Nile branch, dating to the New Kingdom Period, situated near the desert edge west of Luxor. This river branch would have connected important localities and thus played a significant role in the cultural landscape of this area. More recent research conducted further north by Sheisha et al. 2 , near the Giza Plateau, indicated the presence of a former river and marsh-like environment in the floodplain east of the three great Pyramids of Giza.

Even though the largest concentration of pyramids in Egypt are located along a narrow desert strip from south Lisht to Giza, no explanation has been offered as to why these pyramid fields were condensed in this particular area. Monumental structures, such as pyramids and temples, would logically be built near major waterways to facilitate the transportation of their construction materials and workers. Yet, no waterway has been found near the largest pyramid field in Egypt, with the Nile River lying several kilometers away. Even though many efforts to reconstruct the ancient Nile waterways have been conducted, they have largely been confined to small sites, which has led to the mapping of only fragmented sections of the ancient Nile channel systems.

In this work, we present remote sensing, geomorphological, soil coring and geophysical evidence to support the existence of a long-lost ancient river branch, the Ahramat Branch, and provide the first map of the paleohydrological setting in the Lisht-Giza area. The finding of the Ahramat Branch is not only crucial to our understanding of why the pyramids were built in these specific geographical areas, but also for understanding how the pyramids were accessed and constructed by the ancient population. It has been speculated by many scholars that the ancient Egyptians used the Nile River for help transporting construction materials to pyramid building sites, but until now, this ancient Nile branch was not fully uncovered or mapped. This work can help us better understand the former hydrological setting of this region, which would in turn help us learn more about the environmental parameters that may have influenced the decision to build these pyramids in their current locations during the time of Pharaonic Egypt.

Position and morphology of the Ahramat Branch

Synthetic Aperture Radar (SAR) imagery and radar high-resolution elevation data for the Nile floodplain and its desert margins, between south Lisht and the Giza Plateau area, provide evidence for the existence of segments of a major ancient river branch bordering 31 pyramids dating from the Old Kingdom to Second Intermediate Period (2686−1649 BCE) and spanning between Dynasties 3–13 (Fig. 1a ). This extinct branch is referred to hereafter as the Ahramat Branch, meaning the “Pyramids Branch” in Arabic. Although masked by the cultivated fields of the Nile floodplain, subtle topographic expressions of this former branch, now invisible in optical satellite data, can be traced on the ground surface by TanDEM-X (TDX) radar data and the Topographic Position Index (TPI). Data analysis indicates that this lateral distributary channel lies between 2.5 and 10.25 km west from the modern Nile River. The branch appears to have a surface channel depth between 2 and 8 m, a channel length of about 64 km and a channel width of 200–700 m, which is similar to the width of the contemporary neighboring Nile course. The size and longitudinal continuity of the Ahramat Branch and its proximity to all the pyramids in the study area implies a functional waterway of great significance.

a Shows the Ahramat Branch borders a large number of pyramids dating from the Old Kingdom to the 2 nd Intermediate Period and spanning between Dynasties 3 and 13. b Shows Bahr el-Libeini canal and remnant of abandoned channel visible in the 1911 historical map (Egyptian Survey Department scale 1:50,000). c Bahr el-Libeini canal and the abandoned channel are overlain on satellite basemap. Bahr el-Libeini is possibly the last remnant of the Ahramat Branch before it migrated eastward. d A visible segment of the Ahramat Branch in TDX is now partially occupied by the modern Bahr el-Libeini canal. e A major segment of the Ahramat Branch, approximately 20 km long and 0.5 km wide, can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza. Location of e is marked in white a box in a . (ESRI World Image Basemap, source: Esri, Maxar, Earthstar Geographics).

A trace of a 3 km river segment of the Ahramat Branch, with a width of about 260 m, is observable in the floodplain west of the Abu Sir pyramids field (Fig. 1b–d ). Another major segment of the Ahramat Branch, approximately 20 km long and 0.5 km wide can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza (Fig. 1e ). The visible segments of the Ahramat Branch in TDX are now partially occupied by the modern Bahr el-Libeini canal. Such partial overlap between the courses of this canal, traced in the1911 historical maps (Egyptian Survey Department scale 1:50,000), and the Ahramat Branch is clear in areas where the Nile floodplain is narrower (Fig. 1b–d ), while in areas where the floodplain gets wider, the two water courses are about 2 km apart. In light of that, Bahr el-Libeini canal is possibly the last remnant of the Ahramat Branch before it migrated eastward, silted up, and vanished. In the course of the eastward migration over the Nile floodplain, the meandering Ahramat Branch would have left behind traces of abandoned channels (narrow oxbow lakes) which formed as a result of the river erosion through the neck of its meanders. A number of these abandoned channels can be traced in the 1911 historical maps near the foothill of the Western Desert plateau proving the eastward shifting of the branch at this locality (Fig. 1b–d ). The Dahshur Lake, southwest of the city of Dahshur, is most likely the last existing trace of the course of the Ahramat Branch.

Subsurface structure and sedimentology of the Ahramat Branch

Geophysical surveys using Ground Penetrating Radar (GPR) and Electromagnetic Tomography (EMT) along a 1.2 km long profile revealed a hidden river channel lying 1–1.5 m below the cultivated Nile floodplain (Fig. 2 ). The position and shape of this river channel is in an excellent match with those derived from radar satellite imagery for the Ahramat Branch. The EMT profile shows a distinct unconformity in the middle, which in this case indicates sediments that have a different texture than the overlying recent floodplain silt deposits and the sandy sediments that are adjacent to this former branch (Fig. 2 ). GPR overlapping the EMT profile from 600–1100 m on the transect confirms this. Here, we see evidence of an abandoned riverbed approximately 400 m wide and at least 25 m deep (width:depth ratio ~16) at this location. This branch has a symmetrical channel shape and has been infilled with sandy Neonile sediment different to other surrounding Neonile deposits and the underlying Eocene bedrock. The geophysical profile interpretation for the Ahramat Branch at this locality was validated using two sediment cores of depths 20 m (Core A) and 13 m (Core B) (Fig. 3 ). In Core A between the center and left bank of the former branch we found brown sandy mud at the floodplain surface and down to ~2.7 m with some limestone and chert fragments, a reddish sandy mud layer with gravel and handmade material inclusions at ~2.8 m, a gray sandy mud layer from ~3–5.8 m, another reddish sandy mud layer with gravel and freshwater mussel shells at ~6 m, black sandy mud from ~6–8 m, and sandy silt grading into clean, well-sorted medium sand dominated the profile from ~8 to >13 m. In Core B on the right bank of the former branch we found recently deposited brown sandy mud at the floodplain surface and down to ~1.5 m, alternating brown and gray layers of silty and sandy mud down to ~4 m (some reddish layers with gravel and handmade material inclusions), a black sandy mud layer from ~4–4.9 m, and another reddish sandy mud layer with gravel and freshwater mussel shells at ~5 m, before clean, well-sorted medium sand dominated the profile from 5 to >20 m. Shallow groundwater was encountered in both cores concurrently with the sand layers, indicating that the buried sedimentary structure of the abandoned Ahramat Branch acts as a conduit for subsurface water flow beneath the distal floodplain of the modern Nile River.

a Locations of geophysical profile and soil drilling (ESRI World Image Basemap, source: Esri, Maxar, Earthstar Geographics). Photos taken from the field while using the b Electromagnetic Tomography (EMT) and c Ground Penetrating Radar (GPR). d Showing the apparent conductivity profile, e showing EMT profile, and f showing GPR profiles with overlain sketch of the channel boundary on the GPR graph. g Simplified interpretation of the buried channel with the location of the two-soil coring of A and B.

It shows two-soil cores, A and core B, with soil profile descriptions, graphic core logs, sediment grain size charts, and example photographs.

Alignment of old and middle kingdom pyramids to the Ahramat Branch

The royal pyramids in ancient Egypt are not isolated monuments, but rather joined with several other structures to form complexes. Besides the pyramid itself, the pyramid complex includes the mortuary temple next to the pyramid, a valley temple farther away from the pyramid on the edge of a waterbody, and a long sloping causeway that connects the two temples. A causeway is a ceremonial raised walkway, which provides access to the pyramid site and was part of the religious aspects of the pyramid itself 19 . In the study area, it was found that many of the causeways of the pyramids run perpendicular to the course of the Ahramat Branch and terminate directly on its riverbank.

In Egyptian pyramid complexes, the valley temples at the end of causeways acted as river harbors. These harbors served as an entry point for the river borne visitors and ceremonial roads to the pyramid. Countless valley temples in Egypt have not yet been found and, therefore, might still be buried beneath the agricultural fields and desert sands along the riverbank of the Ahramat Branch. Five of these valley temples, however, partially survived and still exist in the study area. These temples include the valley temples of the Bent Pyramid, the Pyramid of Khafre, and the Pyramid of Menkaure from Dynasty 4; the valley temple of the Pyramid of Sahure from Dynasty 5, and the valley temple of the Pyramid of Pepi II from Dynasty 6. All the aforementioned temples are dated to the Old Kingdom. These five surviving temples were found to be positioned adjacent to the riverbank of the Ahramat Branch, which strongly implies that this river branch was contemporaneously functioning during the Old Kingdom, at the time of pyramid construction.

Analysis of the ground elevation of the 31 pyramids and their proximity to the floodplain, within the study area, helped explain the position and relative water level of the Ahramat Branch during the time between the Old Kingdom and Second Intermediate Period (ca. 2649–1540 BCE). Based on Fig. ( 4) , the Ahramat Branch had a high-water level during the first part of the Old Kingdom, especially during Dynasty 4. This is evident from the high ground elevation and long distance from the floodplain of the pyramids dated to that period. For instance, the remote position of the Bent and Red Pyramids in the desert, very far from the Nile floodplain, is a testament to the branch’s high-water level. On the contrary, during the Old Kingdom, our data demonstrated that the Ahramat Branch would have reached its lowest level during Dynasty 5. This is evident from the low altitudes and close proximity to the floodplain of most Dynasty 5 pyramids. The orientation of the Sahure Pyramid’s causeway (Dynasty 5) and the location of its valley temple in the low-lying floodplain provide compelling evidence for the relatively low water level proposition of the Ahramat Branch during this stage. The water level of the Ahramat Branch would have been slightly raised by the end of Dynasty 5 (the last 15–30 years), during the reign of King Unas and continued to rise during Dynasty 6. The position of Pepi II and Merenre Pyramids (Dynasty 6) deep in the desert, west of the Djedkare Isesi Pyramid (Dynasty 5), supports this notion.

It explains the position and relative water level of the Ahramat Branch during the time between the Old Kingdom and Second Intermediate Period. a Shows positive correlation between the ground elevation of the pyramids and their proximity to the floodplain. b Shows positive correlation between the average ground elevation of the pyramids and their average proximity to the floodplain in each Dynasty. c Illustrates the water level interpretation by Hassan (1986) in Faiyum Lake in correlation to the average pyramids ground elevation and average distances to the floodplain in each Dynasty. d The data indicates that the Ahramat Branch had a high-water level during the first period of the Old Kingdom, especially during Dynasty 4. The water level reduced afterwards but was raised slightly in Dynasty 6. The position of the Middle Kingdom’s pyramids, which was at lower altitudes and in close proximity to the floodplain as compared to those of the Old Kingdom might be explained by the slight eastward migration of the Ahramat Branch.

In addition, our analysis in Fig. ( 4) , shows that the Qakare Ibi Pyramid of Dynasty 8 was constructed very close to the floodplain on very low elevation, which implies that the Nile water levels were very low at this time of the First Intermediate Period (2181–2055 BCE). This finding is in agreement with previous work conducted by Kitchen 20 which implies that the sudden collapse of the Old Kingdom in Egypt (after 4160 BCE) was largely caused by catastrophic failure of the annual flood of the Nile River for a period of 30–40 years. Data from soil cores near Memphis indicated that the Old Kingdom settlement is covered by about 3 m of sand 11 . Accordingly, the Ahramat Branch was initially positioned further west during the Old Kingdom and then shifted east during the Middle Kingdom due to the drought-induced sand encroachments of the First Intermediate Period, “a period of decentralization and weak pharaonic rule” in ancient Egypt, spanning about 125 years (2181–2055 BCE) post Old Kingdom era. Soil cores from the drilling program at Memphis show dominant dry conditions during the First Intermediate Period with massive eolian sand sheets extended over a distance of at least 0.5 km from the edge of the western desert escarpment 21 . The Ahramat Branch continued to move east during the Second Intermediate Period until it had gradually lost most of its water supply by the New Kingdom.

The western tributaries of the Ahramat Branch

Sentinal-1 radar data unveiled several wide channels (inlets) in the Western Desert Plateau connected to the Ahramat Branch. These inlets are currently covered by a layer of sand, thus partially invisible in multispectral satellite imagery. In Sentinal-1 radar imagery, the valley floors of these inlets appear darker than the surrounding surfaces, indicating subsurface fluvial deposits. These smooth deposits appear dark owing to the specular reflection of the radar signals away from the receiving antenna (Fig. 5a, b ) 22 . Considering that Sentinel-1’s C-Band has a penetration capability of approximately 50 cm in dry sand surface 23 , this would suggest that the riverbed of these channels is covered by at least half a meter of desert sand. Unlike these former inlets, the course of the Ahramat Branch is invisible in SAR data due in large part to the presence of dense farmlands in the floodplain, which limits radar penetration and the detection of underlying fluvial deposition. Moreover, the radar topographic data from TDX revealed the areal extent of these inlets. Their river courses were extracted from TDX data using the Topographic Position Index (TPI), an algorithm which is used to compute the topographic slope positions and to automate landform classifications (Fig. 5c, d ). Negative TPI values show the former riverbeds of the inlets, while positive TPI signify the riverbanks bordering them.

a Conceptual sketch of the dependence of surface roughness on the sensor wavelength λ (modified after 48 ). b Expected backscatter characteristics in sandy desert areas with buried dry riverbeds. c Dry channels/inlets masked by desert sand in the Dahshur area. d The channels’ courses were extracted using TPI. Negative TPI values highlight the courses of the channels while positive TPI signify their banks.

Analysis indicated that several of the pyramid’s causeways, from Dynasties 4 and 6, lead to the inlet’s riverbanks (Fig. 6 ). Among these pyramids, are the Bent Pyramid, the first pyramid built by King Snefru in Dynasty 4 and among the oldest, largest, and best preserved ancient Egyptian pyramids that predates the Giza Pyramids. This pyramid is situated at the royal necropolis of Dahshur. The position of the Bent Pyramid, deep in the desert, far from the modern Nile floodplain, remained unexplained by researchers. This pyramid has a long causeway (~700 m) that is paved in the desert with limestone blocks and is attached to a large valley temple. Although all the pyramids’ valley temples in Egypt are connected to a water body and served as the landing point of all the river-borne visitors, the valley temple of the Bent Pyramid is oddly located deep in the desert, very distant from any waterways and more than 1 km away from the western edge of the modern Nile floodplain. Radar data revealed that this temple overlooked the bank of one of these extinct channels (called Wadi al-Taflah in historical maps). This extinct channel (referred to hereafter as the Dahshur Inlet due to its geographical location) is more than 200 m wide on average (Fig. 6 ). In light of this finding, the Dahshur Inlet, and the Ahramat Branch, are thus strongly argued to have been active during Dynasty 4 and must have played an important role in transporting building materials to the Bent Pyramid site. The Dahshur Inlet could have also served the adjacent Red Pyramid, the second pyramid built by the same king (King Snefru) in the Dahshur area. Yet, no traces of a causeway nor of a valley temple has been found thus far for the Red Pyramid. Interestingly, pyramids in this site dated to the Middle Kingdom, including the Amenemhat III pyramid, also known as the Black Pyramid, White Pyramid, and Pyramid of Senusret III, are all located at least 1 km far to the east of the Dynasty 4 pyramids (Bent and Red) near the floodplain (Fig. 6 ), which once again supports the notion of the eastward shift of the Ahramat Branch after the Old Kingdom.

a The two inlets are presently covered by sand, thus invisible in optical satellite imagery. b Radar data, and c TDX topographic data reveal the riverbed of the Sakkara Inlet due to radar signals penetration capability in dry sand. b and c show the causeways of Pepi II and Merenre Pyramids, from Dynasty 6, leading to the Saqqara Inlet. The Valley Temple of Pepi II Pyramid overlooks the inlet riverbank, which indicates that the inlet, and thus Ahramat Branch, were active during Dynasty 6. d Radar data, and e TDX topographic data, reveal the riverbed of the Dahshur Inlet with the Bent Pyramid’s causeway of Dynasty 4 leading to the Inlet. The Valley Temple of the Bent Pyramid overlooks the riverbank of the Dahshur Inlet, which indicates that the inlet and the Ahramat Branch were active during Dynasty 4 of the Old Kingdom.

Radar satellite data revealed yet another sandy buried channel (tributary), about 6 km north of the Dahshur Inlet, to the west of the ancient city of Memphis. This former fluvial channel (referred to hereafter as the Saqqara Inlet due to its geographical location) connects to the Ahramat Branch with a broad river course of more than 600 m wide. Data shows that the causeways of the two pyramids of Pepi II and Merenre, situated at the royal necropolis of Saqqara and dated to Dynasty 6, lead directly to the banks of the Saqqara Inlet (see Fig. 6 ). The 400 m long causeway of Pepi II pyramid runs northeast over the southern Saqqara plateau and connects to the riverbank of the Saqqara Inlet from the south. The causeway terminates with a valley temple that lies on the inlet’s riverbank. The 250 long causeway of the Pyramid of Merenre runs southeast over the northern Saqqara plateau and connects to the riverbank of the Saqqara Inlet from the north. Since both pyramids dated to Dynasty 6, it can be argued that the water level of the Ahramat Branch was higher during this period, which would have flooded at least the entrance of its western inlets. This indicates that the downstream segment of the Saqqara Inlet was active during Dynasty 6 and played a vital role in transporting construction materials and workers to the two pyramids sites. The fact that none of the Dynasty 5 pyramids in this area (e.g., the Djedkare Isesi Pyramid) were positioned on the Saqqara Inlet suggests that the water level in the Ahramat Branch was not high enough to enter and submerge its inlets during this period.

In addition, our data analysis clearly shows that the causeways of the Khafre, Menkaure, and Khentkaus pyramids, in the Giza Plateau, lead to a smaller but equally important river bay associated with the Ahramat Branch. This lagoon-like river arm is referred to here as the Giza Inlet (Fig. 7 ). The Khufu Pyramid, the largest pyramid in Egypt, seems to be connected directly to the river course of the Ahramat Branch (Fig. 7 ). This finding proves once again that the Ahramat Branch and its western inlets were hydrologically active during Dynasty 4 of the Old Kingdom. Our ancient river inlet hypothesis is also in accordance with earlier research, conducted on the Giza Plateau, which indicates the presence of a river and marsh-like environment in the floodplain east of the Giza pyramids 2 .

The causeways of the four Pyramids lead to an inlet, which we named the Giza Inlet, that connects from the west with the Ahramat Branch. These causeways connect the pyramids with valley temples which acted as river harbors in antiquity. These river segments are invisible in optical satellite imagery since they are masked by the cultivated lands of the Nile floodplain. The photo shows the valley temple of Khafre Pyramid (Photo source: Author Eman Ghoneim).

During the Old Kingdom Period, our analysis suggests that the Ahramat Branch had a high-water level during the first part, especially during Dynasty 4 whereas this water level was significantly decreased during Dynasty 5. This finding is in agreement with previous studies which indicate a high Nile discharge during Dynasty 4 (e.g., ref. 24 ). Sediment isotopic analysis of the Nile Delta indicated that Nile flows decrease more rapidly by the end of Dynasty 4 25 , in addition 26 reported that during Dynasties 5 and 6 the Nile flows were the lowest of the entire Dynastic period. This long-lost Ahramat Branch (possibly a former Yazoo tributary to the Nile) was large enough to carry a large volume of the Nile discharge in the past. The ancient channel segment uncovered by 1 , 15 west of the city of Memphis through borehole logs is most likely a small section of the large Ahramat Branch detected in this study. In the Middle Kingdom, although previous studies implied that the Nile witnessed abundant flood with occasional failures (e.g., ref. 27 ), our analysis shows that all the pyramids from the Middle Kingdom were built far east of their Old Kingdom counterparts, on lower altitudes and in close proximity to the floodplain as compared to those of the Old Kingdom. This paradox might be explained by the fact that the Ahramat Branch migrated eastward, slightly away from the Western Desert escarpment, prior to the construction of the Middle Kingdom pyramids, resulting in the pyramids being built eastward so that they could be near the waterway.

The eastward migration and abandonment of the Ahramat Branch could be attributed to gradual tilting of the Nile delta and floodplain in lower Egypt towards the northeast due to tectonic activity 28 . A topographic tilt such as this would have accelerated river movement eastward due to the river being located in the west at a relatively higher elevation of the floodplain. While near-channel floodplain deposition would naturally lead to alluvial ridge development around the active Ahramat Branch, and therefore to lower-lying tracts of adjacent floodplain to the east, regional tilting may explain the wholesale lateral migration of the river in that direction. The eastward migration and abandonment of the branch could also be ascribed to sand incursion due to the branch’s proximity to the Western Desert Plateau, where windblown sand is abundant. This would have increased sand deposition along the riverbanks and caused the river to silt up, particularly during periods of low flow. The region experienced drought during the First Intermediate Period, prior to the Middle Kingdom. In the area of Abu Rawash north 29 and Dahshur site 11 , settlements from the Early Dynastic and Old Kingdom were found to be covered by more than 3 m of desert sands. During this time, windblown sand engulfed the Old Kingdom settlements and desert sands extended eastward downhill over a distance of at least 0.5 km 21 . The abandonment of sites at Abusir (5 th Dynasty), where the early pottery-rich deposits are covered by wind-blown sand and then mud without sherds, can be used as evidence that the Ahramat Branch migrated eastward after the Old Kingdom. The increased sand deposition activity, during the end of the Old Kingdom, and throughout the First Intermediate Period, was most likely linked to the period of drought and desertification of the Sahara 30 . In addition, the reduced river discharge caused by decreased rainfall and increased aridity in the region would have gradually reduced the river course’s capacity, leading to silting and abandonment of the Ahramat Branch as the river migrated to the east.

The Dahshur, Saqqara, and Giza inlets, which were connected to the Ahramat Branch from the west, were remnants of past active drainage systems dated to the late Tertiary or the Pleistocene when rainwater was plentiful 31 . It is proposed that the downstream reaches of these former channels (wadis) were submerged during times of high-water levels of the Ahramat Branch, forming long narrow water arms (inlets) that gave a wedge-like shape to the western flank of the Ahramat Branch. During the Old Kingdom, the waters of these inlets would have flowed westward from the Ahramat Branch rather than from their headwaters. As the drought intensified during the First Intermediate Period, the water level of the Ahramat Branch was lowered and withdrew from its western inlets, causing them to silt up and eventually dry out. The Dahshur, Saqqara, and Giza inlets would have provided a bay environment where the water would have been calm enough for vessels and boats to dock far from the busy, open water of the Ahramat Branch.

Sediments from the Ahramat Branch riverbed, which were collected from the two deep soil cores (cores A and B), show an abrupt shift from well-sorted medium sands at depth to overlying finer materials with layers including gravel, shell, and handmade materials. This indicates a step-change from a relatively consistent higher-energy depositional regime to a generally lower-energy depositional regime with periodic flash floods at these sites. So, the Ahramat Branch in this region carried and deposited well-sorted medium sand during its last active phase, and over time became inactive, infilling with sand and mud until an abrupt change led the (by then) shallow depression fill with finer distal floodplain sediment (possibly in a wetland) that was utilized by people and experienced periodic flash flooding. Validation of the paleo-channel position and sediment type using these cores shows that the Ahramat Branch has similar morphological features and an upward-fining depositional sequence as that reported near Giza, where two cores were previously used to reconstruct late Holocene Nile floodplain paleo-environments 2 . Further deep soil coring could determine how consistent the geomorphological features are along the length of the Ahramat branch, and to help explain anomalies in areas where the branch has less surface expression and where remote sensing and geophysical techniques have limitations. Considering more core logs can give a better understanding of the floodplain and the buried paleo-channels.

The position of the Ahramat Branch along the western edge of the Nile floodplain suggests it to be the downstream extension of Bahr Yusef. In fact, Bahr Yusef’s course may have initially flowed north following the natural surface gradient of the floodplain before being forced to turn west to flow into the Fayum Depression. This assumption could be supported by the sharp westward bend of Bahr Yusef’s course at the entrance to the Fayum Depression, which could be a man-made attempt to change the waterflow direction of this branch. According to Römer 32 , during the Middle Kingdom, the Gadallah Dam located at the entrance of the Fayum, and a possible continuation running eastwards, blocked the flow of Bahr Yusef towards the north. However, a sluice, probably located near the village of el-Lahun, was created in order to better control the flow of water into the Fayum. When the sluice was locked, the water from Bahr Yusef was directed to the west and into the depression, and when the sluice was open, the water would flow towards the north via the course of the Ahramat Branch. Today, the abandoned Ahramat Branch north of Fayum appears to support subsurface water flow in the buried coarse sand bed layers, however these shallow groundwater levels are likely to be quite variable due to proximity of the bed layers to canals and other waterways that artificially maintain shallow groundwater. Groundwater levels in the region are known to be variable 33 , but data on shallow groundwater could be used to further validate the delineated paleo-channel of the Ahramat Branch.

The present work enabled the detection of segments of a major former Nile branch running at the foothills of the Western Desert Plateau, where the vast majority of the Ancient Egyptian pyramids lie. The enormity of this branch and its proximity to the pyramid complexes, in addition to the fact that the pyramids’ causeways terminate at its riverbank, all imply that this branch was active and operational during the construction phase of these pyramids. This waterway would have connected important locations in ancient Egypt, including cities and towns, and therefore, played an important role in the cultural landscape of the region. The eastward migration and abandonment of the Ahramat Branch could be attributed to gradual movement of the river to the lower-lying adjacent floodplain or tilting of the Nile floodplain toward the northeast as a result of tectonic activity, as well as windblown sand incursion due to the branch’s proximity to the Western Desert Plateau. The increased sand deposition was most likely related to periods of desertification of the Great Sahara in North Africa. In addition, the branch eastward movement and diminishing could be explained by the reduction of the river discharge and channel capacity caused by the decreased precipitation and increased aridity in the region, particularly during the end of the Old Kingdom.

The integration of radar satellite data with geophysical surveying and soil coring, which we utilized in this study, is a highly adaptable approach in locating similar former buried river systems in arid regions worldwide. Mapping the hidden course of the Ahramat Branch, allowed us to piece together a more complete picture of ancient Egypt’s former landscape and a possible water transportation route in Lower Egypt, in the area between Lisht and the Giza Plateau.

Revealing this extinct Nile branch can provide a more refined idea of where ancient settlements were possibly located in relation to it and prevent them from being lost to rapid urbanization. This could improve the protection measures of Egyptian cultural heritage. It is the hope that our findings can improve conservation measures and raise awareness of these sites for modern development planning. By understanding the landscape of the Nile floodplain and its environmental history, archeologists will be better equipped to prioritize locations for fieldwork investigation and, consequently, raise awareness of these sites for conservation purposes and modern development planning. Our finding has filled a much-needed knowledge gap related to the dominant waterscape in ancient Egypt, which could help inform and educate a wide array of global audiences about how earlier inhabitants were living and in what ways shifts in their landscape drove human activity in such an iconic region.

Materials and methods

The work comprised of two main elements: satellite remote sensing and historical maps and geophysical survey and sediment coring, complemented by archeological resources. Using this suite of investigative techniques provided insights into the nature and relationship of the former Ahramat Branch with the geographical location of the pyramid complexes in Egypt.

Satellite remote sensing and historical maps

Unlike optical sensors that image the land surface, radar sensors image the subsurface due to their unique ability to penetrate the ground and produce images of hidden paleo-rivers and structures. In this context, radar waves strip away the surface sand layer and expose previously unidentified buried channels. The penetration capability of radar waves in the hyper-arid regions of North Africa is well documented 4 , 34 , 35 , 36 , 37 . The penetration depth varies according to the radar wavelength used at the time of imaging. Radar signal penetration becomes possible without significant attenuation if the surface cover material is extremely dry (<1% moisture content), fine grained (<1/5 of the imaging wavelength) and physically homogeneous 23 . When penetrating desert sand, radar signals have the ability to detect subsurface soil roughness, texture, compactness, and dielectric properties 38 . We used the European Space Agency (ESA) Sentinel-1 data, a radar satellite constellation consisting of a C-Band synthetic aperture radar (SAR) sensor, operating at 5.405 GHz. The Sentinel-1 SAR image used here was acquired in a descending orbit with an interferometric wide swath mode (IW) at ground resolutions of 5 m × 20 m, and dual polarizations of VV + VH. Since Sentinal-1 is operated in the C-Band, it has an estimated penetration depth of 50 cm in very dry, sandy, loose soils 39 . We used ENVI v. 5.7 SARscape software for processing radar imagery. The used SAR processing sequences have generated geo-coded, orthorectified, terrain-corrected, noise free, radiometrically calibrated, and normalized Sentinel-1 images with a pixel size of 12.5 m. In SAR imagery subsurface fluvial deposits appear dark owing to specular reflection of the radar signals away from the receiving antenna, whereas buried coarse and compacted material, such as archeological remains appear bright due to diffuse reflection of radar signals 40 .

Other previous studies have shown that combining radar topographic imagery (e.g., Shuttle Radar Topography Mission-SRTM) with SAR images improves the extraction and delineation of mega paleo-drainage systems and lake basins concealed under present-day topographic signatures 3 , 4 , 22 , 41 . Topographic data represents a primary tool in investigating surface landforms and geomorphological change both spatially and temporally. This data is vital in mapping past river systems due to its ability to show subtle variations in landform morphology 37 . In low lying areas, such as the Nile floodplain, detailed elevation data can detect abandoned channels, fossilized natural levees, river meander scars and former islands, which are all crucial elements for reconstructing the ancient Nile hydrological network. In fact, the modern topography in many parts of the study area is still a good analog of the past landscape. In the present study, TanDEM-X (TDX) topographic data, from the German Aerospace Centre (DLR), has been utilized in ArcGIS Pro v. 3.1 software due to its fine spatial resolution of 0.4 arc-second ( ∼ 12 m). TDX is based on high frequency X-Band Synthetic Aperture Radar (SAR) (9.65 GHz) and has a relative vertical accuracy of 2 m for areas with a slope of ≤20% 42 . This data was found to be superior to other topographic DEMs (e.g., Shuttle Radar Topography Mission and ASTER Global Digital Elevation Map) in displaying fine topographic features even in the cultivated Nile floodplain, thus making it particularly well suited for this study. Similar archeological investigations using TDX elevation data in the flat terrains of the Seyhan River in Turkey and the Nile Delta 43 , 44 allowed for the detection of levees and other geomorphologic features in unprecedented spatial resolution. We used the Topographic Position Index (TPI) module of 45 with the TDX data by applying varying neighboring radiuses (20–100 m) to compute the difference between a cell elevation value and the average elevation of the neighborhood around that cell. TPI values of zero are either flat surfaces with minimal slope, or surfaces with a constant gradient. The TPI can be computed using the following expression 46 .

Where the scaleFactor is the outer radius in map units and Irad and Orad are the inner and outer radius of annulus in cells. Negative TPI values highlight abandoned riverbeds and meander scars, while positive TPI signify the riverbanks and natural levees bordering them.

The course of the Ahramat Branch was mapped from multiple data sources and used different approaches. For instance, some segments of the river course were derived automatically using the TPI approach, particularly in the cultivated floodplain, whereas others were mapped using radar roughness signatures specially in sandy desert areas. Moreover, a number of abandoned channel segments were digitized on screen from rectified historical maps (Egyptian Survey Department scale 1:50,000 collected on years 1910–1911) near the foothill of the Western Desert Plateau. These channel segments together with the former river course segments delineated from radar and topographic data were aggregated to generate the former Ahramat Branch. In addition to this and to ensure that none of the channel segments of the Ahramat Branch were left unmapped during the automated process, a systematic grid-based survey (through expert’s visual observation) was performed on the satellite data. Here, Landsat 8 and Sentinal-2 multispectral images, Sentinal-1 radar images and TDX topographic data were used as base layers, which were thoroughly examined, grid-square by grid-square (2*2 km per a square) at a full resolution, in order to identify small-scale fluvial landforms, anomalous agricultural field patterns and irregular ditches, and determine their spatial distributions. Here, ancient fluvial channels were identified using two key aspects: First, the sinuous geometry of natural and manmade features and, second the color tone variations in the satellite imagery. For example, clusters of contiguous pixels with darker tones and sinuous shapes may signify areas of a higher moisture content in optical imagery, and hence the possible existence of a buried riverbed. Stretching and edge detection were applied to enhance contrasts in satellite images brightness to enable the visualization of traces of buried river segments that would otherwise go unobserved. Lastly, all the pyramids and causeways in the study site, along with ancient harbors and valley temples, as indicators of preexisting river channels, were digitized from satellite data and available archeological resources and overlaid onto the delineated Ahramat Branch for geospatial analysis.

Geophysical survey and sediment coring

Geophysical measurements using Ground Penetrating Radar (GPR) and Electromagnetic Tomography (EMT) were utilized to map subsurface fluvial features and validate the satellite remote sensing findings. GPR is effective in detecting changes of dielectric constant properties of sediment layers, and its signal responses can be directly related to changes in relative porosity, material composition, and moisture content. Therefore, GPR can help in identifying transitional boundaries in subsurface layers. EMT, on the other hand, shows the variations and thickness of large-scale sedimentary deposits and is more useful in clay-rich soil than GPR. In summer 2022, a geophysical profile was measured using GPR and EMT units with a total length of approximately 1.2 km. The GPR survey was conducted with a central frequency antenna of 35 MHz and a trigger interval of 5 cm. The EMT survey was performed using the multi-frequency terrain conductivity (EM–34–3) measuring system with a spacing of 10–11 meters between stations. To validate the remote sensing and geophysical data, two sediment cores with depths of 20 m (Core A) and 13 m (Core B) were collected using a deep soil driller. These cores were collected from along the geophysical profile in the floodplain. Sieving and organic analysis were performed on the sediment samples at Tanta University sediment lab to extract information about grain size for soil texture and total organic carbon. In soil texture analysis medium to coarse sediment, such as sands, are typical for river channel sediments, loamy sand and sandy loam deposits can be interpreted as levees and crevasse splays, whereas fine texture deposits, such as silt loam, silty clay loam, and clay deposits, are representative of the more distal parts of the river floodplain 47 .

Data availability

Data for replicating the results of this study are available as supplementary files at: https://figshare.com/articles/journal_contribution/Pyramids_Elevations_and_Distances_xlsx/25216259 .

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Acknowledgements

This work was funded by NSF grant # 2114295 awarded to E.G., S.O. and T.R. and partially supported by Research Momentum Fund, UNCW, to E.G. TanDEM-X data was awarded to E.G. and R.E by the German Aerospace Centre (DLR) (contract # DEM_OTHER2886). Permissions for collecting soil coring and sampling were obtained from the Faculty of Science, Tanta University, Egypt by coauthors Dr. Amr Fhail and Dr. Mohamed Fathy. Bradley Graves at Macquarie University assisted with preparation of the sedimentological figures. Hamada Salama at NRIAG assisted with the GPR field data collection.

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Eman Ghoneim

School of Natural Sciences, Macquarie University, Macquarie, NSW, 2109, Australia

Timothy J. Ralph

Department of History, The University of Memphis, Memphis, TN, 38152-3450, USA

Suzanne Onstine

Near Eastern Languages and Civilizations, University of Chicago, Chicago, IL, 60637, USA

Raghda El-Behaedi

National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, 11421, Egypt

Gad El-Qady, Mahfooz Hafez, Magdy Atya, Mohamed Ebrahim & Ashraf Khozym

Geology Department, Faculty of Science, Tanta University, Tanta, 31527, Egypt

Amr S. Fahil & Mohamed S. Fathy

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Eman Ghoneim conceived the ideas, lead the research project, and conducted the data processing and interpretations. The manuscript was written and prepared by Eman Ghoneim. Timothy J. Ralph co-supervised the project, contributed to the geomorphological and sedimentological interpretations, edited the manuscript and the figures. Suzanne Onstine co-supervised the project, contributed to the archeological and historical interpretations, and edited the manuscript. Raghda El-Behaedi contributed to the remote sensing data processing and methodology and edited the manuscript. Gad El-Qady supervised the geophysical survey. Mahfooz Hafez, Magdy Atya, Mohamed Ebrahim, Ashraf Khozym designed, collected, and interpreted the GPR and EMT data. Amr S. Fahil and Mohamed S. Fathy supervised the soil coring, sediment analysis, drafted sedimentological figures and contributed to the interpretations. All authors reviewed the manuscript and participated in the fieldwork.

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Ghoneim, E., Ralph, T.J., Onstine, S. et al. The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch. Commun Earth Environ 5 , 233 (2024). https://doi.org/10.1038/s43247-024-01379-7

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Avocado plant picture captured in 2011, one year after the tree was stumped [12]. 3.1. Flowering An Avocado tree generally produces more than a million flowers during the flower-ing period, but most of them fall without producing fruit. The Avocado flowers are bisex-ual, which means each flower has both female and male organs. It is ...
Hass Avocado Composition and Potential Health Effects
HASS AVOCADO COMPOSITION. Avocado consumers tend to consume significantly more of key shortfall nutrients—dietary fiber, vitamins K, and E, potassium, and magnesium—in their diet than non-avocado consumers (Fulgoni et al., 2010a).Although the U.S. Nutrition Labeling and Education Act (NLEA) defines the serving size of an avocado as one-fifth of a fruit, or 30 g (1 ounce), the National ...
PDF Nutrient management for avocado (Persea americana miller)
2O, 7-10g Ca, 15-30g Mg; 20-35g S, 0.2-0.5g Zn and B, 0.2g Cu, 0.5-1.0g Fe (Garciana and Ferrat 2001)(Table 3). Gentile et al. (2016) studied the nutrient removal of avocado fruit in Central Highlands of Kenya and based on that they had calculated the organic manure required to fulfill the crop demand.
(PDF) Avocado and its by-products: natural sources of nutrients
The byproducts (seeds and peels) of an avocado cultivated in the south of Colombia were extracted with aqueous acetone and their antioxidant properties were measured with ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) assays, and total polyphenol content was determined by Folin-Ciocalteu method.
Beneficiation of avocado processing industry by-product: A review on
Avocado oil recovery from avocado rip is a mechanical extraction process, however, an additional process is required to remove seeds/stones and pills or skins [14, 15].After removal of pills and seeds, a pulp paste is produced by grinding it and then malaxing at 45-50 °C for 40-60min to obtain the oil (Fig. 1).The avocado oil processing industry generates by-products like skin, rotten ...
The Forgotten Fruit: A Case for Consuming Avocado Within the
The Mediterranean diet is rich in fruits and vegetables and includes an abundant intake of oleic-acid-rich olive oil. People who adhere to a Mediterranean diet have reduced risk for numerous chronic diseases. As obesity rates rise globally, people who choose to follow a traditional Mediterranean diet and/or make improvements in food choices may reduce their risk of metabolic dysfunction and ...
Avocado Seed: A Comparative Study of Antioxidant Content and Capacity
Avocado seeds, which are a residue of the food industry, could be used to obtain extracts with high antioxidant power. In the present study, the most popular radical scavenging methods are presented, establishing a comparison between them, besides working with two different extractions: pure methanol and ethanol-water (50:50 v/v ).
Recent advances in the use of edible coatings for preservation of
Worldwide in 2017, 5.92 million metric tons of avocados were produced, about a 52% increase from the year 2000 (Statista Research Department, 2017). The top two avocado-producing countries are Mexico and Dominican Republic, followed by others like Peru, Indonesia, and Colombia (World Atlas, 2017). Due to the long journeys that avocados can ...
PDF Propagating Avocados
The method is conducive to speedy grafting; a talented propagator can make 600 or 700 grafts a day, with a success rate of 90 percent or better. Suitable scions are about 3/16 to 1/4 inch in diameter. Mter wiping the scion clean, shape its base into a wedge by making opposite, flat, tapered cuts 1 to 2 inches long.
2023 summer warmth unparalleled over the past 2,000 years
Here, we combine observed and reconstructed June-August (JJA) surface air temperatures to show that 2023 was the warmest NH extra-tropical summer over the past 2000 years exceeding the 95% ...
Cubic millimetre of brain mapped in spectacular detail
The 3D map covers a volume of about one cubic millimetre, one-millionth of a whole brain, and contains roughly 57,000 cells and 150 million synapses — the connections between neurons. It ...
PDF Repurposing Fossil Fuel Assets for a Low-Carbon World
Research and Development Grants: In addition to conducting research in government labs, providing research funding to universities and companies can lower the financial barriers to exploring and implementing new technologies for repurposing existing assets. Government Incentives: Governments can make different types of incentives available to
The Egyptian pyramid chain was built along the now abandoned Ahramat
The pyramids of the Western desert in Egypt were built alongside a now extinct branch of the Nile River named as the Ahramat Branch and identified using a combination of radar satellite imagery ...

Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001–2008

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Nutrition Journal

Avocado and its by-products: natural sources of nutrients, phytochemical compounds and functional properties

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Introduction

Nutritional Attributes of Avocados

Health Benefits of Avocados

Nutrient Status

Cardiometabolic Health

Weight Management

Observational Datasets to Assess the Role of Avocado, as Part of a Mediterranean Diet, on Health

Model of Avocado Exchanges in a Mediterranean Dietary Pattern

Production and Consumption of Avocados

Conclusions

Data Availability Statement

Author Contributions

Conflict of Interest

Avocado Seed: A Comparative Study of Antioxidant Content and Capacity in Protecting Oil Models from Oxidation

Gádor Indra Hidalgo

María Pilar Almajano

1. Introduction

2. Results and Discussion

2.2. Protective Effect of ASE in Sunflower Oil Fatty Acid Mixture

2.2.1. Primary Oxidation of Sunflower Oil by Peroxide Value

2.2.2. Secondary Oxidation of Sunflower Oil by TBARs

3. Materials and Methods

3.2. Material and Reagents

3.3. Chemical Analysis

3.3.2. Radical Scavenging Activity

3.3.3. Determination of Methoxy Radical Scavenging Activity by EPR

3.3.4. High Performance Liquid Chromatography (HPLC)

3.3.5. Determination of Primary Oxidation with Peroxide Value (PV) and Secondary Oxidation with TBARs Method

3.3.6. Oxidation Induction Time analysis (OIT-DSC)

4. Conclusions

Abbreviations

Author Contributions

Conflicts of Interest

The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch

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Subsurface structure and sedimentology of the Ahramat Branch

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