The salivary metabolome of children and parental caregivers in a large-scale family environment study.

Human metabolism is complex, and is impacted by genetics, cohabitation, diet, health, and environmental inputs. As such, we applied untargeted LC-MS metabolomics to 1425 saliva samples from a diverse group of elementary school-aged children and their caregivers collected during the Family Life Project, of which 1344 were paired into caregiver/child dyads. We compared metabolomes within and between homes, performed population-wide "metabotype" analyses, and measured associations between metabolites and salivary biomeasures of inflammation, antioxidant potential, environmental tobacco smoke (ETS) exposure, metabolic regulation, and heavy metals. Children and caregivers had similar salivary metabolomes, and dyad explained most metabolomic variation. Our data clustered into two groups, indicating that "metabotypes" exist across large populations. Lastly, several metabolites-putative oxidative damage-associated or pathological markers-were correlated with the above-mentioned salivary biomeasures and heavy metals. Implications of the family environment's effects on metabolomic variation at population, dyadic, and individual levels for human health are discussed.