Page 186

the young infant. Although dietary phosphorus is more abundant than calcium in most U.S. diets with the few exceptions cited, neither inadequate nor excessive intake of phosphorus appears to be a problem. The subcommittee accepts that a 1-to- 1 ratio of calcium to phosphorus will provide sufficient phosphorus for most age groups, but if the calcium intake is adequate, the precise ratio of these minerals is unimportant. The RDA for phosphorus is 800 mg for children 1 to 10 years, 1,200 mg for ages 11 to 24 years, and 800 mg for ages beyond 24. A total allowance of 1,200 mg/day is recommended during pregnancy and lactation.

Infants 

The phosphorus content of human milk, 14 mg/100 g, is adequate for the full-term infant; the calcium-to-phosphorus ratio is 2.3 to 1. The RDA for calcium in infants is based on the poorer absorption of calcium from formulas than from human milk. Allowances for phosphorus are based on a calcium-to-phosphorus ratio of 1.3 to 1 (the same as in cow's milk) during the first 6 months, and 1.2 to 1 for the second 6 months. This declining ratio is consistent with the gradual addition of supplementary foods to the basic milk diet of the newborn. The RDA of formula-fed infants from birth to 6 months of age is 300 mg/day, and that for infants 6 to 12 months is 500 mg/day.

Excessive Intakes and Toxicity

An excess of phosphorus, i.e., a calcium-to-phosphorus ratio lower than 1 to 2, has been shown in several species of animals to lower the blood calcium level and to cause secondary hyperparathyroidism with resorption and loss of bone. In humans, only the effect on blood calcium level has been observed clinically. High-phosphorus human milk substitutes may contribute to the occurrence of hypocalcemic tetany in early infancy (Mizraki et al., 1968), unless calcium levels are increased commensurately. The phosphorus levels present in normal diets are not likely to be harmful—certainly not in the presence of adequate intakes of calcium and vitamin D.

References

Avioli, L.V. 1988. Calcium and phosphorus. Pp. 142-158 in M.E. Shils and V.R. Young, eds. Modern Nutrition in Health and Disease, 7th ed. Lea & Febiger, Philadelphia.

Bloom, W.L., and D. Flinchum. 1960. Osteomalacia with pseudofractures caused by the ingestion of aluminum hydroxide. J. Am. Med. Assoc. 174:1327-1330.