Growth and bone mineralization of normal breast-fed infants and the effects of lactation on maternal bone mineral status

Abstract

To determine if human milk provides for adequate growth and bone mineralization during the lst yr of life, 91 term infants were evaluated. Infants were divided into three groups human milk alone, human milk with supplemental vitamin D, and Similac. Lactating mothers who were receiving supplements of calcium and vitamin D were also studied to determine the effects of lactation on their bone mineral status. Blood was drawn from infants and mothers for measurements of serum calcium, phosphate, alkaline phosphatase, and 25-hydroxyvitamin D. Bone mineral content was measured by photon absorptiometry. Growth was similar between breast-fed and formula-fed infants. Regardless of type of feeding, male infants grew heavier and longer than corresponding female infants. Serum calcium and phosphate levels were similar among the three infant groups: only 25-hydroxyvitamin D levels at 4 months and serum alkaline phosphatase at 2 wk and 6 months of age were different among the three infant groups. Biochemical and vitamin D values were similar among the lactating mothers. There were no differences in infant bone mineral content among the three groups, but male infants had higher bone mineral content than female infants. There were no effects of the duration of lactation of maternal bone mineral content or vitamin D status.