LOW ZINC INTAKE DURING EXCLUSIVE BREAST-FEEDING DOES NOT IMPAIR GROWTH

We studied zinc nutrition in exclusively breast-fed infants whose grow th deviated from the norm. Their number fell from 200 at birth to 116 at the age of 6 months and 36 at the age of 9 months. The mothers rece ived 0, 20, or 40 mg Zn f i as sulfate daily. Breast milk intake and c oncentrations of zinc in milk as well as in maternal and infant serum were measured. Individual zinc concentrations in milk showed channelin g. The 20-mg supplement had no effect on the parameters measured. In c ontrast, 40 mg increased the maternal serum zinc concentration by 2 mo nths and slowed the normal decline of milk zinc concentration by 6 mon ths. Maternal supplementation had no effect on infant serum concentrat ions; they remained lower than adult levels throughout the Ist year of life. Zinc intake was low (about one-tenth of RDA), but it seemed to be adequate; the serum concentrations of the infants were stable after the age of 2 months. Low zinc concentrations in serum were not associ ated with impaired growth. On the contrary, the infants with the highe st rates of growth had the lowest zinc concentrations. The infant seru m zinc concentrations were channeled, but they were also influenced by the zinc intake. Reference values for breast-fed infants are given.