URINARY-EXCRETION OF MAGNESIUM AND CALCIUM AS AN INDEX OF ABSORPTION IS NOT AFFECTED BY LACTOSE INTAKE IN HEALTHY-ADULTS

The effect of lactose on the urinary excretion of Mg and Ca, as an ind ex of absorption, was studied in a double-blind, crossover study durin g three 1-week periods. Twenty-four healthy, lactose-tolerant, adult v olunteers maintained their habitual diets with the exception that all lactose-containing dairy products in the diet were replaced by 600 g/d of three specially prepared dairy products. These products were based on either lactose-enriched cow's milk or lactose-enriched, lactase (E C 3. 2. 1. 23)-treated cow's milk, with or without added Mg, and were given in turn during 1 week. Lactose intake was increased by 127 mmol/ d (46 g/d) while taking the lactose-enriched products. While taking th e Mg-enriched products, Mg intake was increased by 2.8 mmol/d (69 mg/d ) which was equivalent to 17 % of the habitual Mg intake. Apart from t he lactose and Mg intake, nutrient intake was comparable during the th ree dietary periods. Urinary excretions of Mg and Ca were used as indi cators for their absorption. Mg supplementation significantly increase d urinary Mg excretion by 0.97 mmol/d (equivalent to an increase of 18 %, P < 0.001), indicating that urinary Mg excretion is a valid indica tor for intestinal Mg absorption. Hydrolysis of lactose did not affect urinary excretion of Mg and Ca, which implies that lactose intake doe s not affect the absorption of Mg and Ca in healthy adults.