Stable carbon and nitrogen isotopic composition of diet and hair of Gidra-speaking Papuans

Carbon and nitrogen stable isotope ratios of diet of the Japanese and diet-hair offset values

The stable isotope ratios of carbon and nitrogen (δ¹³C and δ¹⁵N) were measured in composite samples of Japanese food and hair. Three hundred eighty-nine foodstuffs were collected in Tokyo and Gunma Prefecture, Japan, in 2020. The foodstuffs were classified into 15 food categories, prepared as usually consumed, and mixed to make 15 composite samples representing each of the food categories. Similarly prepared samples for foodstuffs collected in 2011 and 2015 were also examined. Composite hair samples were collected from a barber shop in Tokyo and a beauty salon in Gunma in 2019. The δ¹³C and δ¹⁵N values of the food and hair composites were measured by elemental analyzer/isotope ratio mass spectrometry after defatting. The δ¹³C and δ¹⁵N values of the food composite varied from composite to composite and according to year of collection. The whole-diet δ¹³C values were -21.1, -22.0, and -21.5 ‰ for the 2011, 2015, and 2020 samples, respectively; the δ¹⁵N values were 5.0, 4.4, and 4.4 ‰, respectively. Diet-hair offset values of δ¹³C and δ¹⁵N were calculated to be 1.9 and 4.3 ‰ for δ¹³C and δ¹⁵N, respectively. These offset values will be important for dietary analysis and nutritional research using hair isotope ratios.

Dietary homogenization and spatial distributions of carbon, nitrogen, and sulfur isotope ratios in human hair in South Korea

Dietary homogenization has progressed worldwide due to westernization and the globalization of food production systems. We investigated dietary heterogeneity in South Korea by examining the spatial distribution of carbon (C), nitrogen (N), and sulfur (S) isotope ratios using 264 human hair samples. Overall, variation in isotope values was small, indicating low dietary heterogeneity. We detected differences in δ¹³C, δ¹⁵N, and δ³⁴S values between administrative provinces and metropolitan cities; inter-regional differences were typically < 1 ‰. Values of δ³⁴S were significantly lower in hair samples from inland regions relative to those from coastal locations, and a similar pattern was observed in δ¹⁵N values. Understanding geographic variation in δ³⁴S and δ¹⁵N values in human hair is useful for provenancing humans in South Korea.

Assessing geographic controls of hair isotopic variability in human populations: A case-study in Canada

Studying the isotope variability in fast-growing human tissues (e.g., hair, nails) is a powerful tool to investigate human nutrition. However, interpreting the controls of this isotopic variability at the population scale is often challenging as multiple factors can superimpose on the isotopic signals of a current population. Here, we analyse carbon, nitrogen, and sulphur isotopes in hair from 590 Canadian resident volunteers along with demographics, dietary and geographic information about each participant. We use a series of machine-learning regressions to demonstrate that the isotopic values in Canadian residents' hair are not only influenced by dietary choices but by geographic controls. First, we show that isotopic values in Canadian residents' hair have a limited range of variability consistent with the homogenization of Canadian dietary habits (as in other industrialized countries). As expected, some of the isotopic variability within the population correlates with recorded individual dietary choices. More interestingly, some regional spatial patterns emerge from carbon and sulphur isotope variations. The high carbon isotope composition of the hair of eastern Canadians relative to that of western Canadians correlates with the dominance of corn in the eastern Canadian food-industry. The gradient of sulphur isotope composition in Canadian hair from coast to inland regions correlates with the increasing soil pH and decreasing deposition of marine-derived sulphate aerosols in local food systems. We conclude that part of the isotopic variability found in the hair of Canadian residents reflects the isotopic signature associated with specific environmental conditions and agricultural practices of regional food systems transmitted to humans through the high consumption rate of intra-provincial food in Canada. Our study also underscores the strong potential of sulphur isotopes as tracers of human and food provenance.

Mapping carbon and nitrogen isotopic composition of fingernails to demonstrate a rural-urban nutrition transition in the Center-West, Northeast, and Amazon regions of Brazil

OBJECTIVE

The main objective of this study is to investigate diet patterns among rural and urban populations of the Center-West, Northeast, and Amazon regions of Brazil through the carbon and nitrogen isotopic composition of fingernails, recognizing that the extent of market integration is a key driver of food consumption.

MATERIALS AND METHODS

In the Center-West, Northeast, and Amazon regions of Brazil, fingernails were sampled in clusters encompassing a major city, town, and rural village. A total of 2,133 fingernails were analyzed. Fingernails were clipped by donors using fingernail clippers. In the laboratory, samples were cleaned then weighed in small tin capsules before being isotopically analyzed for carbon and nitrogen.

RESULTS

The overall mean δ¹³ C and δ¹⁵ N were -19.7 ± 2.8‰ and 10.6 ± 1.1‰, respectively. In the more remote villages, where access to food markets is more challenging, lower δ¹³ C prevails, suggesting that Brazilian staple foods (rice, beans, and farinha) still dominate. In areas with easier access to food markets, δ¹³ C values were higher, suggesting a change to a diet based on C₄ plants, typical of a Brazilian supermarket diet. The variability among inhabitants in the same location expressed by a significant inverse correlation between δ¹³ C and δ¹⁵ N fingernail values suggested that "market integration" does not affect everyone equally in each community.

DISCUSSION AND CONCLUSION

The nutrition transition has not yet reached some remote villages in these regions of Brazil or that the nutrition transition has not yet reached all residents of these remote villages. On the other hand, in several villages there is a considerable adherence to the supermarket diet or that some residents of these villages are already favoring processed food.

Is the 'canine surrogacy approach' (CSA) still valid for dogs and humans in market-oriented and subsistence-oriented communities in Brazil?

Based on the assumptions that human food is available for dogs and isotope diet-tissue differences are similar in dogs and humans, the 'canine surrogacy approach' (CSA) has been used to infer patterns of ancient populations. The goal of this study was to test the CSA in urban (Brasília and Piracicaba) and in rural (Ubatuba and Maraã) areas. The hair C and N isotope ratios of modern dogs were compared with those of human fingernails from different regions of Brazil. Our CSA results showed a correlation between dog and human isotopes values: in rural areas δ¹⁵N of humans and dogs was not statistically different; contrarily, in urban centres, δ¹⁵N of humans was approximately 1 ‰ higher (p < 0.01) than δ¹⁵N of dogs; humans had lower δ¹³C values (p < 0.01) than dogs in Brasília, Piracicaba and Ubatuba. In Maraã, there was not any significant difference between dogs and humans. We concluded that CSA is still valid as a first approach in modern societies. However, isotopic differences found suggest that in modern societies processed dog food is increasingly disconnecting human and dog, jeopardising the use of CSA in the future if the trend of increasing processed dog food consumption continues to occur.

Isotope (δ13C, δ15N, δ2H) diet-tissue discrimination in African grey parrot Psittacus erithacus: implications for forensic studies

Diet-tissue isotopic relationships established under controlled conditions are informative for determining the dietary sources and geographic provenance of organisms. We analysed δ¹³C, δ¹⁵N, and non-exchangeable δ²H values of captive African grey parrot Psittacus erithacus feathers grown on a fixed mixed-diet and borehole water. Diet-feather Δ¹³C and Δ¹⁵N discrimination values were +3.8 ± 0.3 ‰ and +6.3 ± 0.7 ‰ respectively; significantly greater than expected. Non-exchangeable δ²H feather values (-62.4 ± 6.4 ‰) were more negative than water (-26.1 ± 2.5 ‰) offered during feather growth. There was no positive relationship between the δ¹³C and δ¹⁵N values of the samples along each feather with the associated samples of food offered, or the feather non-exchangeable hydrogen isotope values with δ²H values of water, emphasising the complex processes involved in carbohydrate, protein, and income water routing to feather growth. Understanding the isotopic relationship between diet and feathers may provide greater clarity in the use of stable isotopes in feathers as a tool in determining origins of captive and wild-caught African grey parrots, a species that is widespread in aviculture and faces significant threats to wild populations. We suggest that these isotopic results, determined even in controlled laboratory conditions, be used with caution.

Prediction of human dietary δ15N intake from standardised food records: validity and precision of single meal and 24-h diet data

Natural stable isotope ratios (δ¹⁵N) of humans can be used for nutritional analyses and dietary reconstruction of modern and historic individuals and populations. Information about an individual's metabolic state can be obtained by comparison of tissue and dietary δ¹⁵N. Different methods have been used to estimate dietary δ¹⁵N in the past; however, the validity of such predictions has not been compared to experimental values. For a total of 56 meals and 21 samples of 24-h diets, predicted and experimental δ¹⁵N values were compared. The δ¹⁵N values were predicted from self-recorded food intake and compared with experimental δ¹⁵N values. Predicted and experimental δ¹⁵N values were in good agreement for meals and preparations (r = 0.89, p < .001) as well as for the 24-h diets (r = 0.76, p < .001). Dietary δ¹⁵N was mainly determined by the amount of fish, whereas the contribution of meat to dietary δ¹⁵N values was less pronounced. Prediction of human dietary δ¹⁵N values using standardised food records and representative δ¹⁵N data sets yields reliable data for dietary δ¹⁵N intake. A differentiated analysis of the primary protein sources is necessary when relating the proportion of animal-derived protein in the diet by δ¹⁵N analysis.

Carbon and nitrogen stable isotopic offsets between diet and hair/feces in captive chimpanzees

RATIONALE

Estimation of the stable isotopic offsets between tissue and diet is important for dietary reconstructions. Although stable isotopic studies of chimpanzees (Pan troglodytes) are increasing, the isotopic offsets in chimpanzees have never been studied. In this study, the carbon and nitrogen stable isotopic offset values in hair and feces were measured for 13 captive chimpanzees for the first time.

METHODS

All consumed food items and quantities were recorded for each individual for 1 week. Food samples were typically collected three times, hair was collected 3 weeks after the experimental week, and feces were collected ad libitum during the experimental week. The stable carbon and nitrogen isotope ratios were measured using elemental analyzer-isotope ratio mass spectrometry (EA-IRMS).

RESULTS

As the results of Monte Carlo analysis, the estimated carbon and nitrogen offsets between the hair and diet were +3.0 to +3.9‰ and +2.8 to +3.7‰, respectively, for the 95% confidence intervals (CIs). The 95% CIs of the carbon and nitrogen offset values between the feces and diet were -1.6 to 0.0‰ and +1.2 to +2.7‰, respectively.

CONCLUSIONS

These offset values are generally consistent with those of the other primate species reported in previous studies. However, potential variations in the offset values due to dietary and physiological factors should be studied in detail in the future. Copyright © 2016 John Wiley & Sons, Ltd.

Nutritional assessment using stable isotope ratios of carbon and nitrogen in the scalp hair of geriatric patients who received enteral and parenteral nutrition formulas

BACKGROUND & AIMS

The δ¹³C and δ¹⁵N values in the scalp hair of geriatric patients in Japan who received the enteral or parenteral nutrition formula were measured to assess nutritional status.

METHODS

The relations among δ¹³C, δ¹⁵N, calorie intake, BMI, albumin concentration, total cholesterol (T-CHO) and geriatric nutritional risk index (GNRI) in the patients were investigated. Furthermore, the enrichment of δ¹³C and δ¹⁵N from the nutrients to the hair was investigated.

RESULTS

The δ¹³C values in the hair of patients who received enteral nutrition decreased with decreases in the calories received, while the δ¹⁵N values increased, suggesting malnutrition in some patients with a low calorie intake due to a negative nitrogen balance. The distribution of patients with a low calorie intake (below 20 kcal/kg/day) when δ¹³C was plotted against δ¹⁵N differed from that of control subjects, but the distribution of patients with a high calorie intake (above 20 kcal/kg/day) was similar to that of control subjects. No significant differences were observed in BMI, albumin concentration, T-CHO or GNRI between the low and high calorie groups. The enrichment of δ¹³C and δ¹⁵N from the enteral nutrients to the hair were inversely correlated with the δ¹³C and δ¹⁵N in the enteral nutrients. The enrichment levels of δ¹³C and δ¹⁵N tended to be higher and lower, respectively, in the high calorie group. On the other hand, the δ¹³C and δ¹⁵N values in the hair of patients who received parenteral nutrition were higher and lower than those in the control subjects and in the patients who received enteral nutrition, respectively, reflecting the higher δ¹³C and lower δ¹⁵N contents of the parenteral nutrients.

CONCLUSIONS

The δ¹³C and δ¹⁵N values in the hair of patients who received enteral nutrition may be effective indicators for evaluating the long-term nutritional status of geriatric patients. A calorie intake of 20 kcal/kg/day may be a cut-off value for malnutrition in Japanese geriatric patients receiving enteral nutrition. However, caution is necessary when dealing with patients switching from parental nutrition as parenteral nutrition resulted in different changes in δ¹³C and δ¹⁵N. The enrichment levels of δ¹³C and δ¹⁵N from the enteral nutrients to the hair may be inversely correlated with the δ¹³C and δ¹⁵N values of enteral nutrients and vary according to the calorie intake.

Homogeneous diet of contemporary Japanese inferred from stable isotope ratios of hair

The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of −19.4 ± 0.6‰ and 9.4 ± 0.6‰ (mean ± SD), respectively. Within Japan, the inter-regional differences for both isotope ratios was less than 1‰, which indicates low dietary heterogeneity among prefectural divisions. The carbon and nitrogen isotope ratios of the hair showed a significant correlation with the results of questionnaires on self-reported dietary habits. The carbon isotope ratios from Japan were lower than those in samples from the USA but higher than those in samples from Europe. These differences stem from the varying dietary proportions of food products originally derived from C₃ and C₄ plants. The dietary variation of Japan is as small as those of Europe and USA and smaller than those of some Asian countries. These results indicate that dietary homogeneity has progressed in Japan, which may indicate the influence from the spread of the Western-style diet and food globalization, although dietary heterogeneity among countries is still preserved.

Global spatial distributions of nitrogen and carbon stable isotope ratios of modern human hair

RATIONALE

Natural stable carbon (δ(13)C) and nitrogen isotope ratios (δ(15)N) of humans are related to individual dietary habits and environmental and physiological factors. In forensic science the stable isotope ratios of human remains such as hair and nail are used for geographical allocation. Thus, knowledge of the global spatial distribution of human δ(13)C and δ(15)N values is an essential component in the interpretation of stable isotope analytical results.

METHODS

No substantial global datasets of human stable isotope ratios are currently available, although the amount of available (published) data has increased within recent years. We have herein summarised the published data on human global δ(13)C andδ(15)N values (around 3600 samples) and added experimental values of more than 400 additional worldwide human hair and nail samples. In order to summarise isotope ratios for hair and nail samples correction factors were determined.

RESULTS

The current available dataset of human stable isotope ratios is biased towards Europe and North America with only limited data for countries in Africa, Central and South America and Southeast Asia. The global spatial distribution of carbon isotopes is related to latitude and supports the fact that human δ(13)C values are dominated by the amount of C4 plants in the diet, either due to direct ingestion as plant food, or by its use as animal feed. In contrast, the global spatial distribution of human δ(15)N values is apparently not exclusively related to the amount of fish or meat ingested, but also to environmental factors that influence agricultural production.

CONCLUSIONS

There are still a large proportion of countries, especially in Africa, where there are no available data for human carbon and nitrogen isotope ratios. Although the interpretation of modern human carbon isotope ratios at the global scale is quite possible, and correlates with the latitude, the potential influences of extrinsic and/or intrinsic factors on human nitrogen isotope ratios have to be taken into consideration.

Relationships among Mercury Concentration, and Stable Isotope Ratios of Carbon and Nitrogen in the Scalp Hair of Residents from Seven Countries: Effects of Marine Fish and C4 Plants Consumption

We analyzed the Hg concentration, and δ¹³C and δ¹⁵N values in the scalp hair of residents from seven countries; Vietnam, New Zealand, Spain, the USA, South Korea, Brazil and Japan. Relationships among the data in each country and among the seven countries were then examined. The highest Hg concentration as well as the highest or higher δ¹⁵N value in each country was found in the hair of a heavy marine fish-eater, whereas the lowest Hg concentration and δ¹⁵N value were found in the hair of a vegetarian or non (marginal)-fish eater. Hg concentrations were positively correlated with the δ¹⁵N values in each country, and increased markedly in samples with δ¹⁵N values exceeding 9.0 ‰, probably due to fish consumption. The highest Hg concentration could be found in sample, with a δ¹³C value between -19 and -18‰, probably reflecting the δ¹³C value of the marine food web.

Effect of baking and fermentation on the stable carbon and nitrogen isotope ratios of grain-based food

RATIONALE

Isotope ratio mass spectrometry (IRMS) is used extensively to reconstruct general attributes of prehistoric and modern diets in both humans and animals. In order to apply these methods to the accurate determination of specific intakes of foods/nutrients of interest, the isotopic signature of individually consumed foods must be constrained. For example, 86% of the calories consumed in the USA are derived from processed and prepared foods, but the relationship between the stable isotope composition of raw ingredients and the resulting products has not been characterized.

METHODS

To examine the effect of common cooking techniques on the stable isotope composition of grain-based food items, we prepared yeast buns and sugar cookies from standardized recipes and measured bulk δ(13) C and δ(15) N values of samples collected throughout a 75 min fermentation process (buns) and before and after baking at 190°C (buns and cookies). Simple isotope mixing models were used to determine if the isotopic signatures of 13 multi-ingredient foods could be estimated from the isotopic signatures of their constituent raw ingredients.

RESULTS

No variations in δ(13) C or δ(15) N values were detected between pre- and post-baked yeast buns (pre: -24.78‰/2.61‰, post: -24.75‰/2.74‰), beet-sugar cookies (pre: -24.48‰/3.84‰, post: -24.47‰/3.57‰), and cane-sugar cookies (pre: -19.07‰/2.97‰, post: -19.02‰/3.21‰), or throughout a 75 min fermentation process in yeast buns. Using isotopic mass balance equations, the δ(13) C/δ(15) N values of multi-ingredient foods were estimated from the isotopic composition of constituent raw ingredients to within 0.14 ± 0.13‰/0.24 ± 0.17‰ for gravimetrically measured recipes and 0.40 ± 0.38‰/0.58 ± 0.53‰ for volumetrically measured recipes.

CONCLUSIONS

Two common food preparation techniques, baking and fermentation, do not substantially affect the carbon or nitrogen isotopic signature of grain-based foods. Mass-balance equations can be used to accurately estimate the isotopic signature of multi-ingredient food items for which quantitative ingredient information is available.

Development, validation, and use of a semi-quantitative food frequency questionnaire for assessing protein intake in Papua New Guinean Highlanders

OBJECTIVES

The aim of this article was to develop a semi-quantitative food frequency questionnaire (FFQ) and evaluate its validity to estimate habitual protein intake, and investigate current dietary protein intakes of Papua New Guinea (PNG) Highlanders.

METHODS

A 32-item FFQ was developed and tested among 135 healthy male and female volunteers. The FFQ-estimated daily total and animal protein intakes were compared with biomarkers and 3-day Weighed Food Records (WFR) by correlation analyses, Bland-Altman plot analyses and joint classification analyses.

RESULTS

The FFQ-estimated total protein intake significantly correlated with urinary nitrogen in the first morning void after adjusting urinary creatinine concentration (r = 0.28, P < 0.01) and the FFQ-estimated animal protein intake significantly correlated with the hair δ(15) N (Spearman's r = 0.34, P < 0.001). The limits of agreement were ±2.39 Z-score residuals for total protein intake and ±2.19 Z-score for animal protein intake, and intra-individual differences increased as protein intake increased. The classification into the same and adjacent quartiles was 66.0% for total protein intake and 73.6% for animal protein intake. Median daily total and animal protein intake estimates from the FFQ and the 3-day WFR showed a good agreement with differences of 0.2 and 4.9 g, respectively. None of the studied communities in the PNG Highlands met the biologically required protein intake; although the community closer to an urban center showed higher protein intake than the more remote communities.

CONCLUSIONS

The newly developed 32-item FFQ for PNG Highlanders is applicable for evaluation of protein intake at the individual level. Am. J. Hum. Biol. 27:349-357, 2015. © 2014 Wiley Periodicals, Inc.

Isotopic investigation of niche partitioning among native carnivores and the non-native coyote (Canis latrans)

We employed stable carbon (δ(13)C) and nitrogen (δ(15)N) isotopes within a hypothetico-deductive framework to explore potential resource partitioning among terrestrial mammalian carnivores. Isotope values were acquired using guard hair samples from bobcat (Lynx rufus), coyote (Canis latrans), gray fox (Urocyon cinereoargenteus), and red fox (Vulpes vulpes) in the Adirondack Park, NY, USA. Enrichment along the δ(13)C axis was expected to reflect the use of human sources of food (reflecting a corn subsidy), and by extension tolerance for human-modified environments, whereas enrichment along the δ(15)N axis was expected to reflect a higher level of carnivory (i.e. amount of animal-based protein in the diet) - two mechanisms by which these now sympatric species may achieve a dynamic coexistence. Although bobcats were the only obligate carnivore, all four species shared a similar δ(15)N space. In contrast, bobcat had a lower and distinct δ(13)C signature compared to foxes, consistent with the a priori expectation of bobcats being the species least tolerant of human activities. Isotope signatures for coyotes, which colonized the region in the 1920s, overlapped all three native carnivores, bobcats the least, gray fox the most, indicating their potential competitive influence on this suite of native carnivores.

Carbon and nitrogen stable isotope ratios and mercury concentration in the scalp hair of residents from Taiji, a whaling town

We analyzed stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N) as well as mercury (Hg) concentration in the scalp hair of Japanese who consumed whale meat and those who did not, and investigated the relationships among the δ(13)C and δ(15)N values and Hg concentration. The average δ(15)N and δ(13)C values of whale meat-eaters (10.11‰ and -18.5‰) were significantly higher than those of non-eaters (9.28‰ and -18.9‰), respectively. The average Hg concentration of whale meat-eaters (20.6 μg/g) was significantly higher than that of non-eaters (2.20 μg/g). Significant positive correlations were found between the δ(13)C and δ(15)N values and between the δ(15)N value and Hg concentration in the hair of whale meat-eaters, while the correlation between the δ(15)N value and Hg concentration was not statistically significant in the non-eaters. The consumption of whale meat may increase Hg concentration as well as δ(15)N and δ(13)C values in scalp hair.

The diet-body offset in human nitrogen isotopic values: a controlled dietary study

The "trophic level enrichment" between diet and body results in an overall increase in nitrogen isotopic values as the food chain is ascended. Quantifying the diet-body Δ(15) N spacing has proved difficult, particularly for humans. The value is usually assumed to be +3-5‰ in the archaeological literature. We report here the first (to our knowledge) data from humans on isotopically known diets, comparing dietary intake and a body tissue sample, that of red blood cells. Samples were taken from 11 subjects on controlled diets for a 30-day period, where the controlled diets were designed to match each individual's habitual diet, thus reducing problems with short-term changes in diet causing isotopic changes in the body pool. The Δ(15) N(diet-RBC) was measured as +3.5‰. Using measured offsets from other studies, we estimate the human Δ(15) N(diet-keratin) as +5.0-5.3‰, which is in good agreement with values derived from the two other studies using individual diet records. We also estimate a value for Δ(15) N(diet-collagen) of ≈6‰, again in combination with measured offsets from other studies. This value is larger than usually assumed in palaeodietary studies, which suggests that the proportion of animal protein in prehistoric human diet may have often been overestimated in isotopic studies of palaeodiet.

Frozen chicken for wild fish: nutritional transition in the Brazilian Amazon region determined by carbon and nitrogen stable isotope ratios in fingernails

OBJECTIVES

Amazonian populations are experiencing dietary changes characteristic of the nutrition transition. However, the degree of change appears to vary between urban and rural settings. To investigate this process, we determined carbon and nitrogen stable isotope ratios in fingernails and dietary intake of Amazonian populations living along a rural to urban continuum along the Solimões River in Brazil.

METHODS

Carbon and nitrogen stable isotope ratios were analyzed from the fingernails of 431 volunteer subjects living in different settings ranging from rural villages, small towns to urban centers along the Solimões River. Data from 200 dietary intake surveys were also collected using food frequency questionnaires and 24-h recall interviews in an effort to determine qualitative aspects of diet composition.

RESULTS

Fingernail δ(13) C values (mean ± standard deviation) were -23.2 ± 1.3, -20.2 ± 1.5, and -17.4 ± 1.3‰ and δ(15) N values were 11.8 ± 0.6, 10.4 ± 0.8, and 10.8 ± 0.7‰ for those living in rural villages, small towns, and major cities, respectively. We found a gradual increase in the number of food items derived from C(4) plant types (meat and sugar) and the replacement of food items derived from C(3) plant types (fish and manioc flour) with increasing size of urban centers.

CONCLUSION

Increasing urbanization in the Brazilian Amazon is associated with a significant change in food habits with processed and industrialized products playing an increasingly important role in the diet and contributing to the nutrition transition in the region.

Stable isotope analysis of modern human hair collected from Asia (China, India, Mongolia, and Pakistan)

We report isotopic data (delta(2)H, delta(18)O n = 196; delta(13)C, delta(15)N n = 142; delta(34)S n = 85) from human hair and drinking water (delta(2)H, delta(18)O n = 67) collected across China, India, Mongolia, and Pakistan. Hair isotope ratios reflected the large environmental isotopic gradients and dietary differences. Geographic information was recorded in H and O and to a lesser extent, S isotopes. H and O data were entered into a recently developed model describing the relationship between the H and O isotope composition of human hair and drinking water in modern USA and pre-globalized populations. This has anthropological and forensic applications including reconstructing environment and diet in modern and ancient human hair. However, it has not been applied to a modern population outside of the USA, where we expect different diet. Relationships between H and O isotope ratios in drinking water and hair of modern human populations in Asia were different to both modern USA and pre-globalized populations. However, the Asian dataset was closer to the modern USA than to pre-globalized populations. Model parameters suggested slightly higher consumption of locally produced foods in our sampled population than modern USA residents, but lower than pre-globalized populations. The degree of in vivo amino acid synthesis was comparable to both the modern USA and pre-globalized populations. C isotope ratios reflected the predominantly C(3)-based regional agriculture and C(4) consumption in northern China. C, N, and S isotope ratios supported marine food consumption in some coastal locales. N isotope ratios suggested a relatively low consumption of animal-derived products compared to western populations.

Relation between stable isotope ratios in human red blood cells and hair: implications for using the nitrogen isotope ratio of hair as a biomarker of eicosapentaenoic acid and docosahexaenoic acid

BACKGROUND

The nitrogen isotope ratio (expressed as delta(15)N) of red blood cells (RBCs) is highly correlated with the RBC long-chain omega-3 (n-3) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Yup'ik Eskimos. Because delta(15)N can also be measured in hair samples, it could provide a noninvasive, retrospective biomarker for EPA and DHA intakes.

OBJECTIVES

We investigated the agreement between delta(15)N in hair and RBCs and then evaluated the relations between hair delta(15)N and RBC EPA and DHA. We also assessed the agreement in carbon isotope ratios (delta(13)C) between hair and RBCs, because delta(13)C has been proposed as a dietary biomarker in other populations.

DESIGN

We assessed relations between hair and RBC delta(15)N and delta(13)C in a community-based sample of 144 Yup'ik Eskimos and examined the correlations between delta(15)N and RBC EPA and DHA in a subset of these participants (n = 44).

RESULTS

We showed a 1:1 relation with good agreement between hair and RBC delta(15)N (r = 0.91) and delta(13)C (r = 0.87). Hair isotope ratios were greater than RBC ratios by 1.5 per thousand for delta(15)N and by 2.3 per thousand for delta(13)C. There were strong correlations between hair delta(15)N and RBC EPA and DHA (r = 0.83 and 0.84, respectively).

CONCLUSIONS

These results support the use of hair delta(15)N values as a biomarker of EPA and DHA intakes. Because hair collection is noninvasive and the samples require no special processing, studies of EPA and DHA intakes in large populations could use biomarkers rather than self-reports to assess these fatty acids.

Effect of a controlled dietary change on carbon and nitrogen stable isotope ratios of human hair

The carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope ratios of human hair can be used for the interpretation of dietary habits and nutritional status in contemporary or past populations. Although the results of bulk or segmental isotope ratio analysis of human hair have been used for the reconstruction of an individual's diet for years, only limited data of controlled dietary changes on the carbon and nitrogen isotopic composition of human hair are available. Hair of four individuals, two males and two females, who participated in a dietary change experiment for 28 days was segmentally analysed for delta(13)C and delta(15)N. The dietary change included a change from C3 to C4 plant enriched diets and a simultaneous replacement of terrestrial animal products by marine products. This resulted in an increase in delta(13)C(diet) of +8.5 to +9.9 per thousand and in delta(15)N(diet) of +1.5 to +2.2 per thousand. All subjects showed significant increases in delta(13)C(hair) and delta(15)N(hair) during the dietary change period, although no subject reached a new steady state for either carbon or nitrogen. The change in delta(15)N(hair) was faster than the change in delta(13)C(hair) for all individuals. The magnitude of change of the isotopic composition during the dietary change period could be attributed to the degree of physical activity of the individuals, with a higher physical activity resulting in a faster change.

Hair protein and amino acid 13C and 15N abundances take more than 4 weeks to clearly prove influences of animal protein intake in young women with a habitual daily protein consumption of more than 1 g per kg body weight

A high protein or meat intake might be a risk factor for metabolic disorders. Stable isotopic abundances (SIA) of hair can be used as biomarkers for animal protein intake due to characteristic isotopic patterns of food proteins. We investigated if an additional meat intake (M, 200 g pork fillet/day) or an omission of meat and meat products (NOM) can influence the natural (15)N and (13)C SIA within 4 weeks in hair and plasma of young women. The daily protein intake (means +/- SD) was 1.40 +/- 0.29, 2.25 +/- 0.35, and 1.15 +/- 0.26 g/kg at baseline, during M, and during NOM, respectively. At baseline the animal protein intake correlated with bulk SIA of hair ((15)N: R(2) = 0.416; (13)C: R(2) = 0.664; n = 14). However, isotope ratio mass spectrometry (IRMS) analyses have not shown that hair and plasma SIA were changed significantly after M or NOM. Possible reasons were discussed. Urinary SIA were significantly lower after M than after NOM ((15)N: p = 0.039; (13)C: p = 0.006) and close to those of pork fillet. Characteristic patterns of SIA were measured in individual amino acids (AA) by gas chromatography/combustion isotope ratio mass spectrometry (GC/C/IRMS). The results confirmed considerable differences in SIA between AA (delta(15)N, up to 22 per thousand; delta(13)C, up to 31 per thousand). Plots of (15)N versus (13)C abundances in hair revealed characteristic differences between indispensable and dispensable AA. The intervention-dependent changes of AA-specific SIA were not as clear as expected. Although the AA-specific SIA may reveal more detailed characteristics of physiological conditions, further methodological research is required. We suggest that the SIA of leucine can be potential markers of protein intake. The reliability of SIA as biomarkers of protein intake still have to be tested in longer lasting intervention studies in humans. The results may have implications in the assessment for possible benefits and risks of protein consumption.

Correspondence between human diet, body composition and stable isotopic composition of hair and breath in Fijian villagers

The main aim of this work was to describe the relationship between diet, and hair and breath isotopic composition. From one Fijian rural village, hair and breath samples were procured from 20 women. Physical anthropometrics were made, and hair (13)C/(12)C and (15)N/(14)N and breath (13)C/(12)C were measured. Individual diet diaries were kept for two of the four preceding weeks, and isotopic compositions of items which accounted for most of the diet were measured. Individual average diets were analysed for macronutrient and energy content and conform to reasonable nutritional expectation. Characteristics of the diet are described in terms of protein and energy, their patterning with respect to different clusters of food items and their relationship to individuals' anthropometry. Breath CO(2) is depleted in (13)C by 1-2 per thousand on average with respect to the total diet. Hair was enriched on average by 4.1 per thousand in nitrogen and 4.5 per thousand in carbon with respect to the total diet. There was insufficient population variation in hair isotopic composition to establish individual hair-diet isotopic differences. The definite relationship that we establish in this work, between dietary and tissue isotopic values for a human community, provides a basis for determining and validating dietary regimes more generally within non-industrial, non-global-'supermarket' economies.

Clinical-scale investigation of stable isotopes in human blood: delta13C and delta15N from 406 patients at the Johns Hopkins Medical Institutions

Objective chemical biomarkers are needed in clinical studies of diet-related diseases to supplement subjective self-reporting methods. We report on several critical experiments for the development of clinically legitimate dietary stable isotope biomarkers within human blood. Our examination of human blood revealed the following: (1) Within blood clot and serum from anonymous individuals (201 males, 205 females) we observed: mean serum delta13C = -19.1 +/- 0.8 per thousand (standard deviation, SD); clot, -19.3 +/- 0.8 per thousand (SD); range = -15.8 per thousand to -23.4 per thousand. Highly statistically significant differences are observed between clot and serum, males and females for both clot and serum. For 15N (n = 206), mean serum = +8.8 +/- 0.5 per thousand (SD); clot +7.4 +/- 0.4 per thousand (SD); range = +6.3 per thousand to +10.5 per thousand. Blood serum is enriched in 15N relative to blood clot by +1.4 per thousand on average, which may reflect differing protein amino acid content. Serum nitrogen is statistically significantly different for males and females, however, clot shows no statistical difference. (2) Relative to clot, capillary blood is marginally different for 13C, but not 15N. Clot 13C is not significantly different from serum; however, it is depleted in 15N by 1.5 per thousand relative to serum. (3) We assessed the effect of blood additives (sodium fluoride and polymerized acrylamide resin) and laboratory process (autoclaving, freeze drying) commonly used to preserve or prepare venous blood. On average, no alteration in delta13C or delta15N is detected compared with unadulterated blood from the same individual. (4) Storage of blood with and without the additives described above for a period of up to 115 days exhibits statistically significant differences for 13C and 15N for sodium fluoride. However, storage for unadulterated blood and blood preserved with polymerized acrylamide resin does not change the delta13C or delta15N isotopic composition of the blood in a significant way. With these experiments, we gain a clinical context for future development of a stable isotope based dietary biomarker.

Serial analysis of stable nitrogen and carbon isotopes in hair: monitoring starvation and recovery phases of patients suffering from anorexia nervosa

Stable nitrogen and carbon isotopic ratios of hair strands of six patients suffering from anorexia nervosa were measured to monitor a dietary change from near starvation to recovery. This paper presents the results of a first-time study of nitrogen and carbon balance of the patients prior to and after admittance to a hospital and therapy. Sequential analysis of the isotopic ratios of hair strands of all patients could be related to the respective body mass index (BMI) of each patient. Our hypothesis concerning the diachronic change in delta15N and delta13C during therapy was met: The delta15N values were inversely related to the BMI, indicating a slow-down in catabolism of bodily protein due to the process of gluconeogenesis during the starvation phase. In contrast, the delta13C values and BMI were in phase: an increase in BMI resulted in an increase in the delta13C values. This rise in delta13C ratios is best interpreted by an increased supply of protein in the diet. Furthermore, delta15N and delta13C were inversely related. We conclude that hair, which is easily and non-traumatically sampled, is an adequate monitor that reflects dietary change and nitrogen balance within days. This isotopic method may also be applied in forensic studies with regard to cases of deprivation, and starvation, and may be a method for investigating starvation in historic populations.

Nitrogen isotopic composition in hair protein is different in liver cirrhotic patients

The stable-isotopic composition of nitrogen (delta15N) or carbon (delta13C) of body tissues depends on the isotopic composition of food sources and on shifts due to isotopic fractionation during metabolism. As little is known about the effects of pathophysiological conditions we measured delta15N and delta13C values in hair and hair amino acids of patients with cirrhosis (n = 21) and compared the results with those of healthy subjects (n = 100) randomly selected from the 1987-1988 VERA German nutrition survey population. Cirrhosis was reflected in lower hair 15N abundances (6.7 vs. 9.9 per thousand delta15N; P < 0.001) whereas hair 13C abundances did not differ from healthy subjects (-19.4 vs. -19.6 per thousand 13C). Distinct patterns of delta15N and delta13C values were measured in hair amino acids. The delta15N values of phenylalanine were significantly higher in cirrhotics (P < 0.001). With the exception of isoleucine, threonine, and proline all other measured amino acids showed lower delta15N values than healthy subjects (P < 0.001). Lower hair delta15N values were associated with cirrhotic liver disease which suggests that under this condition the altered liver amino acid metabolism affects the nitrogen isotopic composition of the amino acids used for hair protein synthesis. It remains to be determined in controlled studies whether the altered nitrogen isotopic composition directly reflects the pathophysiological condition or is related to differences in dietary protein intake from plant or animal food sources.

Geographical patterns of human diet derived from stable-isotope analysis of fingernails

Carbon and nitrogen isotope ratios of human fingernails were measured in 490 individuals in the western US and 273 individuals in southeastern Brazil living in urban areas, and 53 individuals living in a moderately isolated area in the central Amazon region of Brazil and consuming mostly locally grown foods. In addition, we measured the carbon and nitrogen isotope ratios of common food items to assess the extent to which these isotopic signatures remain distinct for people eating both omnivorous and vegetarian diets and living in different parts of the world, and the extent to which dietary information can be interpreted from these analyses. Fingernail delta13C values (mean +/- standard deviation) were -15.4 +/- 1.0 and -18.8 +/- 0.8 per thousand and delta15N values were 10.4 +/- 0.7 and 9.4 +/- 0.6 per thousand for southeastern Brazil and western US populations, respectively. Despite opportunities for a "global supermarket" effect to swamp out carbon and nitrogen isotope ratios in these two urbanized regions of the world, differences in the fingernail isotope ratios between southeastern Brazil and western US populations persisted, and appeared to be more associated with regional agricultural and animal production practices. Omnivores and vegetarians from Brazil and the US were isotopically distinct, both within and between regions. In a comparison of fingernails of individuals from an urban city and isolated communities in the Amazonian region, the urban region was similar to southeastern Brazil, whereas individuals from isolated nonurban communities showed distinctive isotopic values consistent with their diets and with the isotopic values of local foods. Although there is a tendency for a "global supermarket" diet, carbon and nitrogen isotopes of human fingernails hold dietary information directly related to both food sources and dietary practices in a region.

An objective means of diagnosing anorexia nervosa and bulimia nervosa using 15N/14N and 13C/12C ratios in hair

An objective means based on the carbon and nitrogen stable isotope analysis of five hairs per individual is presented for distinguishing between individuals with anorexia nervosa and/or bulimia nervosa from non-clinical individuals (i.e. clinically normal controls). Using discriminant analysis, an algorithm has been developed that provides both sensitivity and specificity of 80% in making diagnoses of individuals with these eating disorders. With further refinements, the results suggest that it may be also possible to distinguish between individuals with anorexia or bulimia. Finally, the study shows the value of conducting blind tests and using larger sample sizes of both control and treatment groups. Both groups are needed to validate the diagnostic value of a method and to provide measures of sensitivity and specificity of any diagnostic test.

Using stable isotope analysis to obtain dietary profiles from old hair: A case study from Plains Indians

Stable isotope composition of human tissue reflects that of foods consumed, and can provide information about diet independent of artifactual remains. Here we refine and test this method by analyzing nitrogen (delta(15)N) and carbon (delta(13)C) isotope ratios in historic North American Plains Indians hair. Gas-source isotope-ratio mass spectrometry provides high-precision data for both delta(15)N and delta(13)C (+/-0.2 per thousand, 1 sigma) in single hair strands as short as 2 cm (100-150 mug). Because hair contains more carbon than nitrogen, if only delta(13)C data are needed, shorter strands (<1 cm) can be analyzed. This reduction in sample size opens new opportunities for analysis of small hair fragments found in archaeological excavations, as well as for analysis of seasonal variations in long hair strands. We find distinct isotope profiles (delta(15)N vs. delta(13)C) for two cultural groups, the Lower Brule reservation Sioux of 1892 and the reservation Blackfoot of 1892 and 1935. The resultant dietary profiles indicate a higher consumption of meat by the Blackfoot and a higher consumption of maize (or of animals that had fed on maize or other C(4) plants) by the Lower Brule. The two groups of Blackfoot yield similar isotopic profiles despite the passage of four decades, suggesting a strong role for cultural preference even as food sources change. Such stable isotope profiles can be used to link samples from the same cultural tradition based on their similar diets.

Carbon and nitrogen stable isotopic composition of hair protein and amino acids can be used as biomarkers for animal-derived dietary protein intake in humans

The stable nitrogen (15N) and carbon (13C) isotopic composition of tissues reflects the isotopic pattern of food sources. We investigated whether the isotopic composition of human hair can be used as a biomarker to predict the dietary intake of animal-derived food. Hair samples were collected from subjects during a 1987-1988 German nutrition survey (VERA) in which dietary information was collected using a 7-d dietary record. Samples of 50 men and 50 women were randomly selected, in addition to 27 samples of subjects with a reported low meat intake. Isotope ratio MS was used to analyze hair bulk and amino acid-specific isotopic composition. Its relation with and feasibility for predicting animal protein intake were tested using regression analysis and cross-tabulation of observed and predicted dietary data and comparison of the individual values for the binary categories of high and low intake. 15N and 13C abundances strongly predicted relative animal protein and meat intake (R2= 0.31, P < 0.01 and R2= 0.20, P <0.01, respectively). Distinct patterns of individual hair amino acid 15N and 13C abundances were observed. In contrast to bulk values, the isotopic abundances in individual amino acids did not show discriminating ability across sex and isotope-specific categories. We conclude that hair 13C values are as predictive for animal protein consumption as hair 15N values. Bulk isotopic abundance of hair can be used as a biomarker for animal protein intake to validate dietary assessment methods provided that the correlation between isotopic abundances and dietary protein intake is verified in dietary intervention studies.

Choice of dietary protein of vegetarians and omnivores is reflected in their hair protein 13C and 15N abundance

Stable isotopic (15N, 13C) composition of tissues depends on isotopic pattern of food sources. We investigated whether the isotopic compositions of human hair protein and amino acids reflect the habitual dietary protein intake. Hair samples were analyzed from 100 omnivores (selected randomly out of the 1987-1988 German nutrition survey VERA), and from 15 ovo-lacto-vegetarians (OLV), and from 6 vegans recruited separately. Hair bulk and amino acid specific isotopic compositions were analyzed by isotope-ratio mass spectrometry (EA/IRMS and GC/C/IRMS, respectively) and the results were correlated with data of the 7 day dietary records. Hair bulk 15N and 13C abundances clearly reflect the particular eating habits. Vegans can be distinguished from OLV and both are significantly distinct from omnivores in both 15N and 13C abundances. 15N and 13C abundances rose with a higher proportion of animal to total protein intake (PAPI). Individual proportions of animal protein consumption (IPAP) were calculated using isotopic abundances and a linear regression model using animal protein consumption data of vegans (PAPI = 0) and omnivores (mean PAPI = 0.639). IPAP values positively correlated with the intake of protein, meat, meat products, and animal protein. Distinct patterns for hair amino acid specific 15N and 13C abundances were measured but with lower resolution between food preference groups compared with bulk values. In conclusion, hair 13C and 15N values both reflected the extent of animal protein consumption. Bulk isotopic abundance of hair can be tested for future use in the validation of dietary assessment methods.

Carbon isotope analysis of bulk keratin and single amino acids from British and North American hair

The reconstruction of ancient diets using isotopic measurements of bone collagen, and other tissues, which survive in archaeological contexts, relies on known isotopic relationships between diet and body tissues. Examination of these relationships often requires the study of modern human and animal subjects. While hair keratin can act as a useful proxy for bone collagen in isotopic studies on living humans, where it is inappropriate to sample tissues such as collagen, it can, in addition, act as a chronological indicator of dietary change. This study investigates hair keratin delta13C values from current residents of the UK and the USA. Residents in the USA showed a clear bulk hair delta13C enrichment of approximately 3 per thousand over UK individuals, attributed to an elevated C4 dietary input from maize fed to livestock in North America. The keratin delta13C of subjects who moved between the UK and USA showed a pronounced change after relocation, taking approximately 4 months to reach isotopic equilibrium. To investigate these differences further, we measured delta13C values of dispensable and indispensable amino acids as a group, and selected individual amino acids. As a group, enrichment of dispensable amino acids compared with indispensable amino acids occurred in samples from both continents, averaging 7.2 per thousand in the UK and 7.9 per thousand in the USA. Dispensable and indispensable amino acids, as well as all individual amino acids measured, were enriched in samples from the USA compared with those from the UK.

Nitrogen balance and delta15N: why you're not what you eat during pregnancy

Carbon (13C/12C) and nitrogen (15N/14N) stable isotope ratios were longitudinally measured in human hair that reflected the period from pre-conception to delivery in 10 pregnant women. There was no significant change in the delta13C results, but all subjects showed a decrease in delta15N values (-0.3 to -1.1 per thousand) during gestation. The mechanisms causing this decrease in hair delta15N have not been fully elucidated. However, since the delta15N values of dietary nitrogen and urea nitrogen are significantly lower compared to maternal tissues, it is hypothesized that the increased utilization of dietary and urea nitrogen for tissue synthesis during pregnancy resulted in a reduction of the steady state diet to a body trophic level effect by approximately 0.5-1 per thousand. An inverse correlation (R2 = 0.67) between hair delta15N and weight gain was also found, suggesting that positive nitrogen balance results in a reduction of delta15N values independent of diet. These results indicate that delta15N measurements have the ability to monitor not only dietary inputs, but also the nitrogen balance of an organism. A potential application of this technique is the detection of fertility patterns in modern and ancient species that have tissues that linearly record stable isotope ratios through time.

Differential relations between cognition and 15N isotopic content of hair in elderly people with dementia and controls

BACKGROUND

Previous researchers have suggested that a vegetarian diet or one rich in fish may protect against Alzheimer's disease (AD). However, assessing diet is difficult in AD patients. (15)N:(14)N isotopic ratios (delta(15)N) of body proteins can estimate long-term dietary habits in a way that does not depend on memory. delta(15)N is high in people who eat a lot of fish and low in vegetarians.

METHODS

To choose between the vegetarian and fish hypotheses of AD, we compared dietary questionnaire reports and delta(15)N of hair samples from AD patients and controls.

RESULTS

Patients' cognitive scores related directly to reported frequency of eating fish and to hair delta(15)N(AIR), but inversely to reported frequency of eating beans. Homocysteine levels related inversely to hair delta(15)N(AIR) in controls, but not in patients. Dietary questionnaire reports accounted for slightly more variance in delta(15)N(AIR) in patients than controls. Therefore, our questionnaire assessed dietary habits as reliably for individuals with AD as for cognitively unimpaired controls.

CONCLUSIONS

A diet rich in fish may ameliorate AD, possibly by lowering homocysteine, but more vegetarian diets do not. In fact, eating beans correlated with worse cognition in AD patients. Further studies should test if restricting the intake of beans slows the progression of AD.

Stable isotope (13C, 15N and 34S) analysis of the hair of modern humans and their domestic animals

Relationships between dietary status and recent migration were examined by delta(13)C, delta(15)N and delta(34)S analysis of hair samples from 43 modern humans living in a rural community in SW England. The isotopic content of 38 'local' hair samples was compared with that of five recently arrived individuals (from Canada, Chile, Germany and the USA). Hair samples from domestic animals (i.e. mainly cats, dogs, cows and horses) were analysed to examine the difference in delta(13)C, delta(15)N and delta(34)S values between herbivores and carnivores. Generally, modern human hair data from the triple stable isotope (delta(13)C, delta(15)N and delta(34)S) provided enough information to confirm the dietary status and origin of the individual subjects. The dietary intake was generally reflected in the animal hair delta(15)N and delta(13)C values, i.e. highest in the carnivores (cats). However, a non-local origin of food sources given to domesticated omnivores (i.e. dogs) was suggested by their hair delta(34)S values.

[Dietary behavior of the Middle Ages in Grenoble: application of isotopic biogeochemistry of the Saint-Laurent cemetery (XIIIth-XVth centuries, Isère, France)]

Isotopic analysis of 13C and 15N of 47 bones from Saint-Laurent de Grenoble cemetery (Grenoble, Isère), from the end of medieval period (XIIIth-XVth centuries AD) allowed to define the food status of animals with regard to the humans and to discuss the variability amongst adults. Adults who died young and those with small stature may have had diets poor in animal protein. The consumption of animal proteins was more important in the XVth than in the XIVth century and could illustrate a typical urban food economy providing its population with a more diversified diet than in rural areas.

Investigations into the effect of diet on modern human hair isotopic values

Carbon and nitrogen isotopic analysis of body tissues is one of the few techniques that can furnish quantitative information about the diet of archaeological humans. The study of the effects of various diets on modern human isotopic values can help to refine palaeodietary theories, and such work also enables the testing of palaeodietary theories independent of archaeological remains and interpretations. This report discusses the use of modern human hair as a sample material for isotopic analysis. The biogenic carbon and nitrogen isotopic signal is well preserved in hair, and the isotopic values of the keratin can be related to diet. We show that atmospheric and cosmetic contamination of hair keratin does not appear to affect the measured isotopic values. In a small study of Oxford residents, we demonstrate that the magnitude of the nitrogen isotopic values of hair keratin reflects the proportion of animal protein consumed in the diet: omnivores and ovo-lacto-vegetarians have higher delta15N than vegans. There was an observed relationship between the reported amount of animal protein eaten (either meat or secondary animal products) and the nitrogen isotopic values within the two groups of omnivores and ovo-lacto-vegetarians, indicating that an increasing amount of animal protein in the diet results in an increase in the delta15N of hair keratin. This provides the first independent support for a long-held theory that, for individuals within a single population, a diet high in meat equates to elevated nitrogen isotopic values in the body relative to others eating less animal protein. The implications of such results for the magnitude of the trophic level effect are discussed. Results presented here also permit a consideration of the effects of a change of diet in the short and long term on hair keratin isotopic values.

Documenting the diet in ancient human populations through stable isotope analysis of hair

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.