Exploring Early Life Nutrition: Amino Acid Stable Isotopes as Biochemical Markers

This dissertation investigates early childhood diet through compound-specific isotope analysis (CSIA) of amino acids (AAs). Traditional bioarchaeological methods often yield ambiguous results, but CSIA-AA offers a refined approach, distinguishing dietary from non-dietary isotopic changes. Fingernail samples (n = 43) from three contemporary mother-infant dyads were analyzed to assess CSIA-AA’s potential in reconstructing early childhood diet and health. Findings from participants were then applied to study pre-Hispanic breastfeeding and weaning practices in four individuals from Peru’s Jequetepeque Valley. Stable carbon isotope analysis of modern fingernails revealed that glycine and glutamate could track the onset of weaning, while nitrogen isotopes of proline could trace breastmilk consumption. Results also indicated that stable carbon isotopes of glycine and glutamate, along with nitrogen isotopes of phenylalanine, show physiological and pathological stress. Using these biomarkers, results from incremental dentine samples (n = 31) of the four archaeological individuals revealed that weaning ages varied from 2.2 to 3.8 years. To contextualize these findings within broader pre-Hispanic diets, bulk collagen isotopic data from dentine and bone samples (n = 8) from the Jequetepeque Valley were combined with published stable isotope data from seven archaeological sites (AD 100-1532) for Bayesian statistical analysis. This showed that locality and cultural affiliation significantly influenced dietary patterns, affecting children’s nutrition across periods and sites. This study provides valuable insights into pre-Hispanic childhood feeding practices, demonstrating the utility of CSIA-AA in tracking early childhood nutrition and physiological stress. These findings have significant implications for archaeology, nutrition, and ecology, as they establish CSIA-AA as a powerful tool for reconstructing early childhood feeding practices, understanding AA metabolism, and exploring the cultural and health dynamics of past and present populations.