Guidance for the determination of status indicators and dietary requirements for magnesium.

Balance data obtained since 1997 indicate that the Estimated Average Requirement and Recommended Dietary Allowance for magnesium should be 175 and 250 mg/d, respectively, for 70 kg healthy individuals, and increase or decrease based on body weight. Urinary excretion data from balance studies indicate that 40 to 80 mg (1.65 to 3.29 mmol) Mg/day are excreted when magnesium intakes are <250 mg/day, and 80 to 160 mg/day (3.29 to 6.58 mmol) when intakes are >250 mg/day. The change in urinary magnesium excretion with the change in dietary magnesium intake occurs within a few days. Thus, urinary magnesium would be most useful for population studies. Metabolic unit depletion/repletion experiments show that serum magnesium concentrations decrease only after a prolonged depletion if an individual starts with an adequate magnesium status. Individuals with serum magnesium concentrations in excess of 0.75 mmol/L (1.82 mg/dL), or as high as 0.85 mmol/L (2.06 mg/dL), might be magnesium-deficient because such individuals respond to magnesium supplementation. A combination of a dietary intake <250 mg /day, urinary excretion <80 mg (3.29 mmol)/day, and serum magnesium concentration < 0.85 mmol/L (2.06 mg/dL) and preferably <0.80 mmol/L (1.94 mg/dL) could indicate that an individual would respond to magnesium supplementation.