Calcium requirements: new estimations for men and women by cross-sectional statistical analyses of calcium balance data from metabolic studies.

BACKGROUND Low intakes of calcium are associated with an increased risk of both osteoporosis and cardiovascular disease. OBJECTIVE To provide new estimates of the average calcium requirement for men and women, we determined the dietary calcium intake required to maintain neutral calcium balance. DESIGN Calcium balance data [calcium intake -(fecal calcium + urinary calcium)] were collected from 155 subjects [women: n = 73; weight: 77.1 +/- 18.5 kg; age: 47.0 +/- 18.5 y (range: 20-75 y); men: n = 82; weight: 76.6 +/- 12.5 kg; age: 28.2 +/- 7.7 y (range: 19-64 y)] who participated in 19 feeding studies conducted in a metabolic unit. Balance data from the final 6-12 d of each dietary period (minimum length:18 d) of each study (1-9 observations per subject) were analyzed. Data were excluded if individual intakes of magnesium, copper, iron, phosphorus, or zinc fell below the estimated average requirements or exceeded the 99 th percentile of usual intakes from the 1994 Continuing Survey of Food Intakes by Individuals (for iron, above the upper limit). Daily intakes of calcium ranged between 415 and 1740 mg. The relation between intake and output was examined by fitting random coefficient models. Coefficients were included to test for sex and age differences. RESULTS The models predicted a neutral calcium balance [defined as calcium output (Y) equal to calcium intake (C)] at intakes of 741 mg/d [95% prediction interval (PI): 507, 1035; Y = 148.29 + 0.80C], 9.4 mg kg body wt(-1) d(-1) [95% PI: 6.4, 12.9; Y = 1.44 + 0.85C], or 0.28 mg kcal(-1) d(-1) [95% PI: 0.19, 0.38; Y = 0.051 + 0.816C]. Neither age nor sex affected the estimates when calcium intakes were expressed as mg/d or as mg kg body wt(-1) d(-1). CONCLUSION The findings suggest that the calcium requirement for men and women is lower than previously estimated.