Recalculation of the calcium requirement of adult men.

BACKGROUND There is uncertainty about the calcium requirement with particular respect to age and sex differences and the calculation of skin calcium losses. OBJECTIVE We calculated the calcium requirement of adult men from a homogenous set of calcium balances and a robust estimate of calcium loss through the skin. DESIGN We reviewed available high-quality published calcium balances in men and retrieved 219 balances; we noted a fall in calcium absorption in individuals >60 y of age. Our analysis was confined to 157 men ≤59 y of age with intakes of ≤1100 mg Ca. RESULTS The mean age of the men was 38 y (range: 17-59 y), and the mean duration of the balances was 107 d (9-480 d). We assumed skin calcium losses of 40 mg Ca/d on the basis of the calcium content of insensible water loss. There was a highly significant correlation between calcium intake and the net absorbed calcium (R(2) = 0.59), but inspection and physiologic considerations led us to use the logarithmic transformation of intake, which yielded the equation Ca absorbed = 210 log Ca intake - 1135 mg Ca. The calcium intake at which urine calcium plus skin calcium losses were equal to the net absorbed calcium was rounded to 750 mg Ca as the requirement, which implied a recommended allowance of 900 mg Ca. CONCLUSION We conclude that the mean calcium requirement of adult men <60 y of age is 750 mg Ca/d, and the Recommended Dietary Allowance should be 900 mg Ca.