Thirty-eight lactating women, from 1 to 31 months postpartum, provided monthly milk samples for determination of calcium, magnesium, manganese, copper, iron, and zinc. Subjects remained in the study an average of 4 consecutive months, with a maximum participation of 9 months. Subject variation accounted for the majority of variance in the raw data. After statistically controlling subject effect, copper, iron, and zinc levels were shown to be significantly related to duration of lactation. Prediction equations for these three minerals were developed, making it possible to calculate, on an individual basis, the copper, iron, and zinc levels of milk to be produced in future months. Data were also collected to determine possible correlations between breast milk mineral levels and the maternal dietary intake, serum levels, or hair concentration of these same minerals. No significant correlation was found between the milk mineral content and any of the three parameters under study.

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Lead was measured in the milk of 39 lactating women to determine if the concentration posed a toxicological hazard to nursing infants. Blood and hair of these women were also analyzed for lead to establish possible correlations with milk, and to indicate body burdens. The women were categorized as rural or urban residents so that all mean values of lead could then be correlated with their locations. The mean levels of lead in milk, blood, and hair were 3, 119 ng/ml and 2002 ng/g (ppb), respectively. Lead levels in milk were not considered high enough to pose any threat to the nursing infant. Furthermore, the levels in blood and hair were below values typically cited as average. The three biological parameters did not correlate significantly with each other or with the location of these women. Therefore, it does not appear that the women in this study have high body burdens of lead, or that the nursing infant is at any risk of lead exposure via milk.

For those interested in another approach to breast-feeding, Jelliffe and Jelliffe have recently published an elegant paper titled " Breast Is Best."4 Developing skills that enhance breast-feeding can be learned by reading the books listed at the end of this article. If pediatricians want to be strong advocates of breast-feeding, they must be convinced of the advantages of breast milk. Many physicians say that they support breast-feeding but will, for instance, send formula bottles to the bedside of a breast-feeding mother. The antagonistic physician or member of the office team may make remarks such as "Are you going to breast-feed until your child goes to school?" " Are you still breast-feeding?" or " The baby needs solid foods for good nutrition." These innuendos can defeat and demoralize the breast-feeding mother. Unless the physician provides strong support against these remarks, the mother will lose her confidence. Many husbands who are advocates of breast-feeding will defend her against these discouraging remarks. Group sessions of lactating mothers also bolster morale. Many mothers find duenna substitutes whom they can communicate with by telephone. (A duenna is an elderly woman who has charge of young unmarried women in a Spanish family.) However, when breast-feeding mothers confront a serious problem for which they have no simple solution, the pediatrician has to provide the ultimate backup support.