Osteoporosis therapy: don't forget the phosphorus - Literature Review & Commentary - Brief Article

Townsend Letter for Doctors and Patients,  June, 2003  by Alan R. Gaby

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The effect of calcium intake on the absorption of phosphorus was assessed in 543 studies of healthy women aged 35-65 years and in 93 men and women aged 19-78 years. Mean net absorption of phosphorus was 60.3% for the first group and 53% for the second group. For each 500-mg increase in calcium intake, phosphorus absorption decreased by 166 mg.

Comment: This study indicates that increasing dietary intake of calcium decreases the absorption of phosphorus. A deficiency of phosphorus can lead to impaired bone mineralization, which might account for the equivocal results seen in some calcium supplementation trials. The authors of the present study point out that one of the most effective trials in elderly patients used tricalcium phosphate as the calcium source (N Engi J Med 1992;327:1637-42). The interaction between calcium and phosphorus should not be of concern for many individuals, since most Western diets contain ample or excessive amounts of phosphorus. However, individuals with marginal nutritional status (such as the elderly) who supplement with large amounts of calcium may be at risk of developing phosphorus deficiency. The presence of a low serum or urinary phosphorus level may indicate low or suboptimal phosphorus status. When the potential for calcium-induced phosphorus deficiency is a concern, it may be advisable to administer a proportion of the supplemental calcium in the form of a calcium phosphate preparation (e.g., Posture[R]).

Heaney RP, Nordin BEC. Calcium effects on phosphorus absorption: implications for the prevention and co-therapy of osteoporosis. J Am Coll Nutr 2002;21:239-244.

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