The Urinary Excretion of Magnesium as an Effective Magnesium Deficiency State Indicator: A Controlled Intervention Trial

Abstract

With the western influence in our diets, food consumption has changed, and our magnesium (Mg) intake is no longer optimal. Serum Mg (S-Mg) level is currently used as an indicator of Mg deficiency and is strictly regulated via compensatory mechanisms. It is believed that a 24-h urine collection can be used to evaluate potential Mg deficiency. This study aimed to assess whether Mg deficiency state as found in urine Mg (U-Mg) excretion and improving such deficiency with a diet that meets the Recommended Dietary Allowances (RDAs) of Mg for 15 d. Healthy Japanese women were recruited for Study 1 (n=22) and Study 2 (n=10). Study 1 was 1-d balance test, where fasting blood and 24-h urine samples were collected. Study 2 was 15-d diet load test, where fasting blood (days 1, 7, and 15) and 24-h urine (odd days) were collected. All test meals were made certain to have met the RDA for Mg for women in their 20s. In Studies 1 and 2, S-Mg was within the normal range. In Study 1, U-Mg excretion was 67.7±17.0 mg/d, with a large dispersion. In Study 2, U-Mg excretion on days 7 and 15 was significantly higher than on day 1, but have no significant differences in U-Mg excretion between days 7–15. U-Mg excretion can be a valu-able indicator to evaluate Mg state. In young women, improvements in Mg deficient state were observed after 7–15 d of taking meals that met the RDAs of Mg.