Evaluation of the magnesium status in athletics

The purpose of this study was to examine the magnesium balance in endurance athletes. Clarification was to be obtained whether the athletes are more frequently magnesium-deficient than non-athletic persons. In addition, a check was made whether dietary factors are responsible for the onset of magnesium deficiency. 50 volunteers with a mean age of 25 years were enrolled in this randomized, prospective study. Based on a cycle ergometry test women with an aerobic-anaerobic threshold above 2.4 W/kg (n=7) and men above 2.6 W/kg (n=18) were assigned to the group of endurance athletes, the remaining 25 subjects formed the control group (8 women and 17 men), The athletes reported training at least 9 hours per week, the subjects in the control group less than 9 hours per week. Since earlier studies had shown that a serum magnesium concentration within the normal range does not necessarily exclude a magnesium deficiency, and magnesium retention can provide more precise information on the magnesium status using a magnesium loading test, the magnesium retention, plasma magnesium concentration, ionized fraction of plasma magnesium, erythrocytic magnesium concentration, renal magnesium excretion and oral magnesium intake were measured. The mean magnesium retention values in the control group measured using the intravenous magnesium loading test were lower than those in the endurance athletes. No differenees were found in the mean values of plasma magnesium concentration ionized fractions of plasma magnesium and erythrocytic magnesium concentration in the two groups, while the endurance trained subjects excreted significantly more magnesium via the kidneys and had a higher oral magnesium intake than the controt group. The study thus confirms that endurance athletes are more frequently magnesium-deficient than persons who do not engage in endurance sports. This deficiency was caused by elevated renal magnesium excretion. Although the athletes' magnesium intake with food was higher, the magnesium quantity consumed did not suffice to maintain a balanced magnesium status.