Mineral and vitamin D adequacy in infants fed human milk or formula between 6 and 12 months of age

During the latter half of an infant's year, adequate mineral and vitamin D intakes may be important not only for the prevention of rickets but also for the attainment of optimal adult peak bone mass. Ingestion of 400 IU vitamin D per day, either as a supplement or contained in formula or table milk, will result in normal serum concentrations of vitamin D, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D. Human milk from a vitamin D-sufficient mother provides a marginal amount, less than 100 IU/L/day of total vitamin D activity from the vitamin D and 25-hydroxyvitamin D. Infants exclusively fed human milk of vitamin D-deficient mothers, who do not receive additional vitamin D or adequate exposure to sunlight, are at significant risk for vitamin D-deficiency rickets. The low concentration of phosphorus in human milk is adequate for most term infants but probably compounds any vitamin D deficiency. Intake or phosphorus from formula or table milk is more than adequate, and the addition of baby foods increases this mineral's intake to generous levels. Calcium is well absorbed and adequate in human milk if vitamin D is sufficient, but concern exists about calcium intake from infant formulas for this older group. My colleagues and I have conducted studies of bone mineral content and mineral homeostasis in term infants fed human milk (300 mg/L calcium), standard cow milk formula (440/mg/L/calcium), or a soybean formula (600 mg/L calcium); our findings suggest that all three types of feedings provided comparable bone mineralization and normal indicators of mineral homeostasis. Mean calcium retentions at 6 months, 9 months, and 12 months in all three groups were between 138 and 205 mg/day, substantially more than the 130 mg/day estimated to be needed from body composition data. Estimates for phosphorus were similarly generous. The questions of whether higher calcium intakes will result in further increases in bone mineral content and of the effect of beikost on calcium absorption from different milks require further study.