Effect of magnesium supplementation on the fractional intestinal absorption of (CaCl2)-Ca-45 in women with a low erythrocyte magnesium concentration

The cosupplementation of magnesium with calcium has been suggested to be be neficial in the prevention of osteoporosis. We investigated the effect of m agnesium supplementation on parameters of bone resorption and fractional Ca -45 absorption. Twenty apparently healthy women with a mean age of 39.2 +/- 9.2 years and an erythrocyte magnesium concentration less than 1.97 mmol/L were recruited into a controlled magnesium supplementation trial. During w eeks 1 to 4, they received a daily control preparation, potassium/sodium ci trate malate (PSCM). During weeks 5 to 8, the subjects received magnesium c itrate malate (MCM) equivalent to 250 mg magnesium per day. During the four th and eighth weeks, blood was collected for measurement of the serum intac t parathyroid hormone (PTH) concentration and serum and erythrocyte magnesi um concentration, urine was collected for measurement of calcium, magnesium , creatinine, and deoxypyridinoline excretion. On the final day of each tre atment period, 5 mu Ci (CaCl2)-Ca-45 was administered orally, and the isoto pe was traced in the blood and urine over 7 hours. Urinary calcium, Ca-45, and deoxypyridinoline excretion, as well as serum intact PTH levels, showed no statistically significant changes as a result of magnesium supplementat ion. However, urinary magnesium excretion increased by 31.1% (P < .005) whi le fractional Ca-45 absorption decreased by 23.5% (P < .001) as a result of magnesium supplementation. It is concluded that magnesium supplementation does not result in changes in bone resorption, while the fractional intesti nal absorption of Ca-45 appears to decrease. Copyright (C) 2000 by W.B. Sau nders Company.