Influence of mineral intake and use of oral contraceptives before pregnancy on the mineral content of human colostrum and of more mature milk

Abstract

The influence of mineral intake and of long-term use of oral contraceptives (OCA) before pregnancy on the mineral content of milk was studied in healthy lactating women. Previous use of OCA did not significantly affect the concentrations of calcium, magnesium, zinc, copper, or iron in colostrum on day 3 or in more mature milk on day 14 of lactation. However, manganese concentration was significantly lower in colostrum and in milk of subjects who had used OCA. Serum copper levels were decreased in subjects who had used OCA and were increased by copper supplements but concomitant changes in copper levels in milk were not observed. Intakes of calcium, magnesium, or zinc had no influence on the levels of these minerals in milk. Levels of zinc in milk were similar when mean intakes of zinc were 11 or 28 mg/day. Regardless of the effects of OCA, manganese concentration in milk increased significantly during the first 2 weeks of lactation whereas zinc concentration decreased. Zinc concentration decreased from 4.65 ppm in colostrum to less than 0.5 ppm after 1 year of lactation. Concentrations of calcium and magnesium in milk did not change significantly with the progression of lactation. The levels of calcium, magnesium, zinc, copper, and manganese in colostrum were significantly positively correlated with the concentrations of the minerals on day 14. Little diurnal variation was observed in the levels of calcium, magnesium, and zinc in milk.