A promising approach in isotope geochemistry: 87Sr/86Sr in human teeth and hair to study dietary and environmental effects

In recent years Sr isotope geochemistry has provided a huge contribution to environmental and food traceability studies. This is possible because soils, plants and water are characterized by a specific Sr isotopic signature (expressed through the 87Sr/86Sr ratio), which derives from the local geological substratum which, in turn, depends on geological processes and on the age and initial rubidium (Rb) content of the rocks, given that 87Rb decays to 87Sr over time. Since the relative abundance of Sr isotopes does not change during the path through the food chain, the 87Sr/86Sr ratio in human tissues reflects that of the “environment” in which people live and feed. In particular, tooth enamel (which forms during the first years of life) does not exchange with external Sr after mineralization. For this reason, its isotopic composition mostly reflects the 87 Sr/86Sr of the food intake that individuals used for energy, growth and maintaining the processes of life, during their childhood. In this work, the Sr isotopic characterization of deciduous human teeth and hair, water, soil, plants and food was carried out. Donors are all born and currently residing in Campania (Southern Italy), of different age and sex. The 87Sr/86Sr of deciduous teeth provides a direct link to the mother’s milk, or to the artificial milk, which are the first foods for the newborn individuals, whereas the 87 Sr/86Sr of hair is directly related to the diet in adulthood. Moreover, the mother’s milk is in part related to the local geological substratum and in part to the diet that has become no longer local, but global. Despite adult individuals have different diets, the isotopic fingerprint of enamel teeth is similar for all breastfeed children. Results from this study have scientific implications also for human mobility studies.