INFLUENCE OF A MIXED AND A VEGETARIAN DIET ON URINARY MAGNESIUM EXCRETION AND CONCENTRATION

Urinary Mg is suggested to be an effective inhibitor of the formation and growth of calcium oxalate stones. In order to examine the influenc e of variations in dietary Mg on urinary Mg excretion, ten healthy mal e subjects were kept on two different standard diets for 5 d each. In the course of the test period, 24 h urine samples were collected. Diet s 1 and 2 were calculated according to the dietary recommendations of the German Society of Nutrition (Deutsche Gesellschaft fur Ernahrung, 1986). Diet 1 was established as a model of a balanced mixed diet, whe reas diet 2 represented an ovo-lacto-vegetarian meal plan. Diets 1 and 2 were isoenergetic with equal amounts of the main nutrients, estimat ed from food tables, and a constant fluid intake. In contrast to the c ontent of Mg (336 mg) and dietary fibre (28 g) of diet 1, diet 2 was r ich in Mg (553 mg) and dietary fibre (52 g). On the ingestion of diet 1, renal Mg excretion was 5.09 (SEM 0.35) mmol on the control day and increased slightly but not significantly to 5.40 (SEM 0.52) mmol on th e corresponding day on diet 2. Urinary Mg excretion as a percentage of estimated dietary intake was about double on the balanced mixed diet (37%) than on the Mg-rich vegetarian diet (24%). As both diets contain ed equal amounts of most nutrients, these results indicate a lower exc retion rate of Mg from the vegetarian diet than from the mixed diet. T his would appear to be primarily due to the higher Mg and fibre conten ts and to the lower Mg utilization, that are important factors in decr easing Mg absorption and consequently urinary excretion rate.