Stable isotopes in the different trophic levels reveal regional divergence in dietary habits among Tibetan pastoralists

Understanding geographical variation and driving mechanisms of the dietary habits of Tibetan pastoralists is a key to improving their health status under climate change and globalization. Characterization of diet via isotopic signatures along the length of the local food chain could provide this information. We analyzed δ13C and δ15N of soil, plants, animals and pastoralists at different geographical sites ranging in a gradient of easily accessible to remote areas. The high δ15N values in soil and plants were not recovered in animals and pastoralists, indicating use of external feed and food resources respectively. The mean δ13C (-22.0‰) and δ15N values (6.9‰) of pastoralists indicated diets consisting mainly of native C3 plants and animal products. Pastoralists living in the remotest areas maintained more traditional dietary habits based on native animal products. However, dietary changes of pastoralists were triggered by external food resources and alterations in ecological chain of easily accessible areas.