Zinc, calcium, and magnesium concentrations in milk from American and Egyptian women throughout the first 6 months of lactation.

Effects of stage of lactation, nutrient intake, and cultural differences on the composition of human milk were examined during the first 6 mo of lactation in American and Egyptian women. In both population groups zinc levels in milk decreased from 1 to 6 months of lactation. American women supplemented with Zn had higher levels of Zn in their milk than did unsupplemented American or Egyptian women. Concentrations of calcium and magnesium were not significantly different in milk of American and Egyptian women except at month 6 of lactation. Ca levels in milk of both population groups increased from 1 to 2-3 mo of lactation and then decreased at 6 mo; Mg concentrations increased from 1 to 3 mo and then reached a plateau. Similarities in the longitudinal decrease observed in Zn levels of milk in Zn supplemented and unsupplemented subjects suggested physiological regulation.