Magnesium requirements: new estimations for men and women by cross-sectional statistical analyses of metabolic magnesium balance data

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 (>= 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 (Pl): 113, 237 mg/d; Y = 19.8 + 0.880 M], 2.36 mg (.) kg(-1) (.) d(-1) (95% PI-1.581, 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.