Documenting the diet in ancient human populations through stable isotope analysis of hair.
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Fundamental to the understanding of human history is the ability to make interpretations based on artefacts and other remains which are used to gather information about an ancient population. Sequestered in the organic matrices of these remains can be information, for example, concerning incidence of disease, genetic defects and diet. Stable isotopic compositions, especially those made on isolates of collagen from bones, have been used to help suggest principal dietary components. A significant problem in the use of collagen is its long-term stability, and the possibility of isotopic alteration during early diagenesis, or through contaminating condensation reactions. In this study, we suggest that a commonly overlooked material, human hair, may represent an ideal material to be used in addressing human diets of ancient civilizations. Through the analysis of the amino-acid composition of modern hair, as well as samples that were subjected to radiation (thus simulating ageing of the hair) and hair from humans that is up to 5200 years old, we have observed little in the way of chemical change. The principal amino acids observed in all of these samples are essentially identical in relative abundances and content. Dominating the compositions are serine, glutamic acid, threonine, glycine and leucine, respectively accounting for approximately 15%, 17%, 10%, 8% and 8% of the total hydrolysable amino acids. Even minor components (for example, alanine, valine, isoleucine) show similar constancy between the samples of different ages. This constancy clearly indicates minimal alteration of the amino-acid composition of the hair. Further, it would indicate that hair is well preserved and is amenable to isotopic analysis as a tool for distinguishing sources of nutrition. Based on this observation, we have isotopically characterized modern individuals for whom the diet has been documented. Both stable nitrogen and carbon isotope compositions were assessed, and together provide an indication of trophic status, and principal type (C3 or C4) of vegetation consumed. True vegans have nitrogen isotope compositions of about 7/1000 whereas humans consuming larger amounts of meat, eggs, or milk are more enriched in the heavy nitrogen isotope. We have also analysed large cross-sections of modern humans from North America and Europe to provide an indication of the variability seen in a population (the supermarket diet). There is a wide diversity in both carbon and nitrogen isotope values based at least partially on the levels of seafood, corn-fed beef and grains in the diets. Following analysis of the ancient hair, we have observed similar trends in certain ancient populations. For example, the Coptics of Egypt (1000 BP) and Chinchorro of Chile (5000-800 BP) have diets of similar diversity to those observed in the modern group but were isotopically influenced by local nutritional sources. In other ancient hair (Egyptian Late Middle Kingdom mummies, ca. 4000 BP), we have observed a much more uniform isotopic signature, indicating a more constant diet. We have also recognized a primary vegetarian component in the diet of the Neolithic Ice Man of the Oetztaler Alps (5200 BP). In certain cases, it appears that sulphur isotopes may help to further constrain dietary interpretations, owing to the good preservation and sulphur content of hair. It appears that analysis of the often-overlooked hair in archaeological sites may represent a significant new approach for understanding ancient human communities. (+info)
Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men.
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BACKGROUND: Vegetarians have lower platelet and plasma concentrations of n-3 polyunsaturated fatty acids (PUFAs) than do omnivores. We recently showed that male vegetarians have higher platelet aggregability than do omnivores. OBJECTIVE: We investigated whether male vegetarians (n = 17) who consumed an increased amount of dietary alpha-linolenic acid (ALA) showed any changes in their tissue profile of PUFAs, plasma thromboxane concentrations, platelet aggregability, or hemostatic factors. DESIGN: During the study, all subjects maintained their habitual vegetarian diets except that a proportion of dietary fat was replaced with vegetable oils and margarines that were provided. Initially, all subjects consumed a low-ALA diet (containing safflower oil and safflower oil-based margarine) for 14 d; they then consumed either a moderate-ALA diet (containing canola oil and canola oil-based margarine) or a high-ALA diet (containing linseed oil and linseed oil-based margarine) for 28 d. Blood samples were collected at day 0 (baseline), day 14, and day 42. RESULTS: Eicosapentaenoic acid, docosapentaenoic acid, total n-3 PUFAs, and the ratio of n-3 to n-6 PUFAs were significantly increased (P < 0.05), whereas the ratio of arachidonic acid to eicosapentaenoic acid was decreased (P < 0.05), in platelet phospholipids, plasma phospholipids, and triacylglycerols after either the moderate-ALA or high-ALA diet compared with the low-ALA diet. No significant differences were observed in thrombotic risk factors. CONCLUSION: ALA from vegetable oils (canola and linseed) has a beneficial effect on n-3 PUFA concentrations of platelet phospholipids and plasma lipids in vegetarian males. (+info)
Fish intake, independent of apo(a) size, accounts for lower plasma lipoprotein(a) levels in Bantu fishermen of Tanzania: The Lugalawa Study.
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Plasma lipoprotein(a) [Lp(a)] levels are largely genetically determined by sequences linked to the gene encoding apolipoprotein(a) [apo(a)], the distinct protein component of Lp(a). Apo(a) is highly polymorphic in length due to variation in the numbers of a sequence encoding the apo(a) kringle 4 domain, and plasma levels of Lp(a) are inversely correlated with apo(a) size. In 2 racially homogeneous Bantu populations from Tanzania differing in their dietary habits, we found that median plasma levels of Lp(a) were 48% lower in those living on a fish diet than in those living on a vegetarian diet. Considering the relationship between apo(a) size and Lp(a) plasma concentration, we have extensively evaluated apo(a) isoform distribution in the 2 populations to determine the impact of apo(a) size in the determination of Lp(a) values. The majority of individuals (82% of the fishermen and 80% of the vegetarians) had 2 expressed apo(a) alleles. Additionally, the fishermen had a high frequency of large apo(a) isoforms, whereas a higher frequency of small isoforms was found in the vegetarians. When subjects from the 2 groups were matched for apo(a) phenotype, the median Lp(a) value was 40% lower in Bantus on the fish diet than in those on the vegetarian diet. A significant inverse relationship was also found between plasma n-3 polyunsaturated fatty acids and Lp(a) levels (r=-0.24, P=0.01). The results of this study are consistent with the concept that a diet rich in n-3 polyunsaturated fatty acids, and not genetic differences, is responsible for the lower plasma levels of Lp(a) in the fish-eating Bantus and strongly suggest that a sustained fish-based diet is able to lower plasma levels of Lp(a). (+info)
Lipoprotein(a), essential fatty acid status and lipoprotein lipids in female Australian vegetarians.
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In the present study we investigated serum lipoprotein(a) [Lp(a)] levels, plasma lipids, the serum phospholipid polyunsaturated fatty acid profile and correlates of serum Lp(a) in healthy free-living female vegetarians (n=50) and omnivores (n=24) to assess differences which may have implications for cardiovascular risk. Dietary saturated fat and total plasma cholesterol were significantly lower in the vegetarians compared with omnivores. The mean serum Lp(a) concentration was lower in the vegetarians (171 mg/l) than in the omnivores (247 mg/l). The serum Lp(a) concentration was significantly negatively correlated with carbohydrate intake (as % of energy), and positively correlated with plasma total cholesterol. Compared with the omnivores, the vegetarians had significantly lower concentrations of 20:3,n-6, 20:4,n-6, 22:5,n-6, 20:5,n-3, 22:6,n-3 and total n-6 and n-3 polyunsaturated fatty acids, and a lower n-3/n-6 polyunsaturated fatty acid ratio, in serum phospholipids. Lower concentrations of plasma total cholesterol, serum phospholipid total fatty acids, total saturated fatty acids and arachidonic acid, and a tendency towards a lower serum Lp(a) concentration, in vegetarians may have beneficial effects on cardiovascular disease risk. However, the decreased concentration of serum phospholipid n-3 polyunsaturated fatty acids may potentially promote thrombotic risk. Based on the present data, it would seem appropriate for omnivores to reduce their dietary intake of total fat and saturated fat in order to decrease their plasma cholesterol, and vegetarians should perhaps increase their dietary intake of n-3 polyunsaturated fatty acids, and thus improve the balance of n-3/n-6, in order to reduce any thrombotic tendency that might increase their generally low risk of cardiovascular disease. (+info)
Oestradiol and sex hormone-binding globulin in premenopausal and post-menopausal meat-eaters, vegetarians and vegans.
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Endogenous oestradiol is strongly associated with breast cancer risk but its determinants are poorly understood. To test the hypothesis that vegetarians have lower plasma oestradiol and higher sex hormone-binding globulin (SHBG) than meat-eaters we assayed samples from 640 premenopausal women (153 meat-eaters, 382 vegetarians, 105 vegans) and 457 post-menopausal women (223 meat-eaters, 196 vegetarians, 38 vegans). Vegetarians and vegans had lower mean body mass indices (BMI) and lower plasma cholesterol concentrations than meat-eaters, but there were no statistically significant differences between meat-eaters, vegetarians and vegans in pre- or post-menopausal plasma concentrations of oestradiol or SHBG. Before adjusting for BMI there were small differences in the direction expected, with the vegetarians and vegans having higher SHBG and lower oestradiol (more noticeable amongst post-menopausal women) than the meat-eaters. These small differences were essentially eliminated by adjusting for BMI. Thus this study implies that the relatively low BMI of vegetarians and vegans does cause small changes in SHBG and in post-menopausal oestradiol, but that the composition of vegetarian diets may not have any additional effects on these hormones. (+info)
Dietary intake and iron status of Australian vegetarian women.
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BACKGROUND: Despite the possible overall health benefits of a vegetarian diet, there is concern that some vegetarians and infrequent meat eaters, particularly females, may have inadequate iron status because of low or no heme-iron intakes. OBJECTIVE: The objective was to investigate the nutritional intake and iron status of vegetarian women. DESIGN: The nutritional intakes of 50 free-living vegetarian women aged 18-45 y and 24 age-matched omnivorous control women were assessed by using 12-d weighed dietary records. Iron status was assessed by measuring hemoglobin and serum ferritin concentrations. RESULTS: There was no significant difference between mean (+/-SD) daily iron intakes of vegetarians and omnivores (10.7 +/- 4.4 and 9.9 +/- 2.9 mg, respectively), although heme-iron intakes were low in the vegetarians. Vegetarians had significantly lower intakes of protein (P < 0.01), saturated fat (P < 0.01), and cholesterol (P < 0.001), and significantly higher intakes of dietary fiber (P < 0.001) and vitamin C (P < 0.05). Mean serum ferritin concentrations were significantly lower (P = 0.025) in vegetarians (25.0 +/- 16.2 microg/L) than in omnivores (45.5 +/- 42.5 microg/L). However, similar numbers of vegetarians (18%) and omnivores (13%) had serum ferritin concentrations <12 microg/L, which is a value often used as an indicator of low iron stores. Hemoglobin concentrations were not significantly different. CONCLUSION: It is important that both vegetarian and omnivorous women maintain an adequate iron status and follow dietary practices that enhance iron absorption. (+info)
Convergence of philosophy and science: the third international congress on vegetarian nutrition.
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Populations of vegetarians living in affluent countries appear to enjoy unusually good health, characterized by low rates of cancer, cardiovascular disease, and total mortality. These important observations have fueled much research and have raised 3 general questions about vegetarians in relation to nonvegetarians: Are these observations the result of better nondietary lifestyle factors, such as lower prevalences of smoking and higher levels of physical activity?; Are they the result of lower intakes of harmful dietary components, in particular meat?; and Are they the result of higher intakes of beneficial dietary components that tend to replace meat in the diet? Current evidence suggests that the answer to all 3 questions is "Yes." Low smoking rates contribute importantly to the low rates of cardiovascular disease and many cancers, probably including colon cancer, in Seventh-day Adventists and other vegetarian populations. Also, avoidance of red meat is likely to account in part for low rates of cardiovascular disease and colon cancer, but this does not appear to be the primary reason for general good health in these populations. Evidence accumulated in the past decade emphasizes the importance of adequate consumption of beneficial dietary factors-rather than just the avoidance of harmful factors-including an abundance of fruit, vegetables, and whole grains and regular consumption of vegetable oils, including those from nuts. Although current knowledge already provides general guidance toward healthy diets, accumulated evidence now strongly indicates that diet has a powerful yet complex effect on health and that further investigation is needed. (+info)
Health effects of vegetables and fruit: assessing mechanisms of action in human experimental studies.
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Epidemiologic data support the association between high intake of vegetables and fruits and low risk of chronic disease. There are several biologically plausible reasons why consumption of vegetables and fruit might slow or prevent the onset of chronic diseases. Vegetables and fruit are rich sources of a variety of nutrients, including vitamins, trace minerals, and dietary fiber, and many other classes of biologically active compounds. These phytochemicals can have complementary and overlapping mechanisms of action, including modulation of detoxification enzymes, stimulation of the immune system, reduction of platelet aggregation, modulation of cholesterol synthesis and hormone metabolism, reduction of blood pressure, and antioxidant, antibacterial, and antiviral effects. Although these effects have been examined primarily in animal and cell-culture models, experimental dietary studies in humans have also shown the capacity of vegetables and fruit and their constituents to modulate some of these potential disease-preventive mechanisms. The human studies have relied on intermediate endpoints related to disease risk. Design methodologies used include multiple-arm trials, randomized crossover studies, and more compromised designs such as nonrandomized crossovers and pre- and posttreatment analyses. Length of treatment ranged from a single dose to years depending on the mechanism of interest. Stringency of dietary control varied from addition of supplements to a habitual diet to provision of all food for the duration of a treatment. Rigorously conducted experimental dietary studies in humans are an important link between population- and laboratory-based research. (+info)