Posted 07 December 2007 - 02:44 AM
Am J Clin Nutr. 2007 Oct;86(4):1054-63.
Calcium requirements: new estimations for men and women by cross-sectional statistical analyses of calcium balance data from metabolic studies.
Hunt CD, Johnson LK.
US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. curtiss.hunt@ars.usda.gov
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 ©] 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.
PMID: 17921384
Am J Clin Nutr. 2006 Oct;84(4):843-52.
Magnesium requirements: new estimations for men and women by cross-sectional statistical analyses of metabolic magnesium balance data.
Hunt CD, Johnson LK.
US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. chunt@gfhnrc.ars.usda.gov
BACKGROUND: Current recommendations for magnesium requirements are based on sparse balance data. OBJECTIVE: To provide new estimates of the average magnesium requirement for men and women, we pooled magnesium data from 27 different tightly controlled balance studies conducted at the US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND. DESIGN: Magnesium balance data (magnesium intake - [fecal magnesium + urinary magnesium]) (664 data points) were collected from 243 subjects (women: n = 150; weight: 71.6 +/- 16.5 kg; age: 51.3 +/- 17.4 y; men: n = 93, weight: 76.3 +/- 12.5 kg; age: 28.1 +/- 8.1 y). Data from the last 6-14 d of each dietary period (> or =28 d) of each study were analyzed and were excluded if individual intakes of calcium, copper, iron, phosphorus, or zinc fell below respective estimated average requirements (EARs) or exceeded 99th percentiles of usual intakes of those elements (iron: above the upper limit) from the 1994 Continuing Survey of Food Intakes by Individuals. Daily intakes of magnesium ranged between 84 and 598 mg. The relation between magnesium intake and magnesium output was investigated by fitting random coefficient models. RESULTS: The models predicted neutral magnesium balance [defined as magnesium output (Y) equal to magnesium intake (M)] at magnesium intakes of 165 mg/d [95% prediction interval (PI): 113, 237 mg/d; Y = 19.8 + 0.880 M], 2.36 mg . kg(-1) . d(-1) (95% PI: 1.58, 3.38 mg . kg(-1) . d(-1); Y = 0.306 + 0.870 M), or 0.075 mg . kcal(-1) . d(-1) (95% PI: 0.05, 0.11 mg . kcal(-1) . d(-1); Y = 0.011 + 0.857 M). Neither age nor sex affected the relation between magnesium intake and output. CONCLUSION: The findings suggest a lower magnesium requirement for healthy men and women than estimated previously.
PMID: 17023712