Calcium and phosphorus metabolism in full-term infants

Appropriate intake of dietary calcium and phosphorus is essential for the maintenance of mineral homeostasis and support of adequate bone mineralization in growing infants. Disturbances of calcium homeostasis such as newborn hypocalcemia, have been shown to be secondary to high oral phosphate intake. The incidence of hypocalcemic tetany has changed from epidemic proportions in newborns, who were formerly fed evaporated cow's milk formula, to the present sporadic occurrence in newborns who are now fed humanized cow's milk formula, with a calcium concentration of about 50 mg/dl and a phosphorus concentration of about 35 mg/dl. Human milk, provided vitamin D intake is adequate, has been shown to maintain calcium-phosphorus homeostasis and support adequate bone mineralization at least in the first 6 months of life. After this, the phosphorus content of breast milk could limit mineral accretion in exclusively breast fed infants. The present concentration of calcium and phosphorus in the humanized cow's milk formulas support adequate mineral homeostasis and bone mineralization throughout the first year of life. As bone calcium content is proportional to calcium intake, feeding whole cow's milk from early infancy onward is associated with abnormal bone mineralization. The adequacy of bone mineralization in infants fed soy formula is still controversial.