Human dietary δ¹⁵N intake: Representative data for principle food items

Dietary analysis using δ¹⁵N values of human remains such as bone and hair is usually based on general principles and limited data sets. Even for modern humans, the direct ascertainment of dietary δ ¹⁵N is difficult and laborious, due to the complexity of metabolism and nitrogen fractionation, differing dietary habits and variation of δ¹⁵N values of food items. The objective of this study was to summarize contemporary regional experimental and global literature data to ascertain mean representative δ¹⁵N values for distinct food categories. A comprehensive data set of more than 12,000 analyzed food samples was summarized from the literature. Data originated from studies dealing with (1) authenticity tracing or origin control of food items, and (2) effects of fertilization or nutrition on δ¹⁵N values of plants or animals. Regional German food δ¹⁵N values revealed no major differences compared with the mean global values derived from the literature. We found that, in contrast to other food categories, historical faunal remains of pig and poultry are significantly enriched in ¹⁵N compared to modern samples. This difference may be due to modern industrialized breeding practices. In some food categories variations in agricultural and feeding regimens cause significant differences in δ¹⁵N values that may lead to misinterpretations when only limited information is available.