Distinguishing vegan-, vegetarian-, and omnivorous diets by hair isotopic analysis.

Background: Dietary risks contribute heavily to disability-adjusted life years (DALYs), being more important than hypertension, obesity, or smoking. To measure dietary exposure remains a challenge in nutrition research.

Aims: The aim of the present study was to test the hypothesis that isotope ratios of N and C in human hair could distinguish between subjects adhering to different habitual diets.

Methods: 20 male and 29 female subjects average 31 years old (range 19-53), with stable dietary habits volunteered. Diets were vegan, vegetarian and omnivorous. Hair samples were processed on an elemental analyser coupled to isotope-ratio mass spectrometry.

Results: δN differed between vegan, vegetarian and omnivorous diets, p < 0.05 for all. δC differed between vegan and omnivorous diets, p < 0.05, but neither of these diets were separated from the vegetarian diet.

Conclusion: Elemental Analysis of δC and especially δN with isotope ratio mass spectrometry seems to be a promising, non-invasive and objective way to distinguish groups of subjects on different habitual diets, at least if n=>10.