Studies in human lactation: zinc, copper, manganese and chromium in human milk in the first month of lactation.

Zinc, copper, manganese and chromium were measured in a total of 259 samples of human milk from 11 women from day of delivery to 31 days postpartum. Milk intakes by their fully breast-fed infants were calculated from 24-h test-weighing measurements. Zinc was analyzed by flame atomic absorption spectrophotometry, and the other elements by graphite furnace atomic absorption. Mean (+/- SD) concentrations declined from a maximum of 11.5 +/- 4.7 micrograms/ml at 2 days to 2.98 +/- 0.78 micrograms/ml at 28 +/- 3 days. Changes in the other three elements were irregular. The average copper concentration declined from 0.6 +/- 0.12 micrograms/ml on day 5 to 0.41 +/- 0.04 micrograms/ml at 28 days. Manganese levels decreased from a mean of 5.4 +/- 1.6 ng/ml on day 1 to 2.7 +/- 1.6 ng/ml on day 5; from 8 to 28 days there was little change, the overall mean being 3.7 +/- 2.2 ng/ml. The average concentration of chromium over the whole period was 0.27 +/- 0.10 ng/ml. Average daily intakes of the elements, by the infants, over the one month period were: zinc, 2.0 mg; copper, 0.25 mg; manganese, 2.0 micrograms; chromium, 150 ng.