Mineral content of colostrum and mature milk of lactating Nigerian women as influenced by stage of lactation.

380 milk samples (96 colostrum and 284 mature milk samples) collected from 240 lactating Nigerian women within the first 9 months of lactation were analyzed for zinc, copper, iron, calcium, and magnesium concentrations by atomic absorption spectrophotometry. Mean levels of zinc, copper, iron, calcium, and magnesium in colostrum were 5.83, 0.52, 0.55, 400, and 33 mcg/ml, respectively; the levels for the same minerals in mature milk collected in the 8th and 12th week of lactation were 3.08, 0.29, 0.38, 300, and 31 mcg/ml, respectively. While milk levels of all minerals decreased with increase in lactation age, zinc levels showed the fastest rate of decrease. Milk zinc levels at the 9th month were only 13% of that in colostrum. Similar percentages for copper, iron, calcium, and magnesium were 49, 60, 34, and 74%, respectively. Estimates of intake by solely breastfed infants during the first 6 months showed gross inadequacies when compared with Recommended Daily Allowances. Results suggest the need for early supplementation, especially as zinc deficiencies as well as a high incicdence of iron deficiency anemia has been reported in Nigerian infants.