Carbon and Nitrogen Isotope Composition of Australasian Hair and Fingernails in a Global Context.

RATIONALE

The stable carbon (δC) and nitrogen (δN) isotope composition of human bone and tissues encodes dietary information that in some circumstances can be attributed to geographical location. While there is a global dataset amounting to > 4000 samples, limited data are available for the Australasian region.

METHODS

One hundred and seven nail/hair samples were detergent and solvent pretreated and analysed for δC and δN composition, sourced from individuals normally residing in southern Australia (temperate), northern Australia (seasonal tropical) and urban Papua New Guinea (tropical). Isotope values for nails were converted to hair keratin equivalent values using accepted fractionation factors. The results were compared with each other, and with the global datasets available from Europe, Asia, Africa and the Americas.

RESULTS

The southern Australian and Papua New Guinean data exhibit a similar mean and range to each other for both δC and δN values, comparable to results for some regions of Europe and Asia. The northern Australian data extends to higher δC values than the other groups due to a greater component of carbon in the diet ultimately from a C source. Vegetarians exhibit a similar range to the omnivores in δC but tend to lower δN values.

CONCLUSIONS

Global supply chains and industrial fertilizer use have reduced the range δC and nitrogen δN values in the samples in this study, as has been the case globally. The range of values observed reflects the ability of consumers to access local produce from supermarkets or local markets. The Australasian data tend to lower δC values than the global average, indicating a dominance of carbon assimilated by C photosynthesis in the diet. While similar to some European and Asian populations, δC values are lower than from regions with a high reliance on carbon assimilated by C photosynthesis, including the Americas and parts of Africa.