During the latter half of an infant's first 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 of
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.