Trace element levels in mature breast milk of recently lactating Japanese women.

BACKGROUND: Many trace elements are essential for infant growth and development during early life. Their concentrations in breast milk vary depending on social and economic factors. Nonetheless, the present available values in Japan were derived from lactating mothers approximately 15 years ago. METHODS: Healthy mothers who gave birth to a single infant after 37 weeks of gestation at Teikyo University Hospital were recruited between July 2016 and December 2017. They were encouraged to collect breast milk samples and a self-administered food frequency questionnaire at 1 and 3 months postpartum. Anthropometric data for the mothers and their infants were also collected. Overall, 79 subjects were analyzed after excluding subjects with inadequate data in the food frequency questionnaire, insufficient breast milk samples, and medication that could affect dietary intakes. Trace element concentrations were determined by inductively coupled plasma mass spectrometry, and their correlation with several factors were investigated. RESULTS: Trace element concentrations were widely distributed as previously reported. Median concentrations of Cr, Mn, Fe, Cu, Zn, Se, and Mo were 0.8, 0.8, 98, 50, 272, 2.2, and 0.7 µg/dL at 1 month postpartum and 0.6, 0.7, 55, 33, 177, 2.1, and 0.7 µg/dL at 3 months postpartum, respectively. There were no correlations between trace element concentrations and either mothers' intakes or infants' growth. In contrast, there were significant correlations between several trace elements and macronutrients in addition to inter-element correlations among almost all trace elements. CONCLUSIONS: Trace element concentrations in mature breast milk were determined from recently lactating mothers in Japan.