Effects of dietary magnesium level on calcium absorption in growing male rats

The effects of dietary magnesium level (0.025, 0.05, and 0.15% magnesium) on calcium absorption were studied in growing rats fed the diets containing 0.5% calcium. The apparent calcium absorption rate and the retention rate of rats fed diets containing 0.15% magnesium were significantly lower than those of rats fed diets containing 0.05% magnesium. On the other hand, apparent magnesium absorption and retention were significantly increased dose-dependently. Femoral bone mineral density (BMD) of rats fed diets containing 0.15% magnesium was significantly lower than that of rats fed diets containing 0.025% and 0.05% magnesium. The amounts of femoral calcium of rats fed diets containing 0.15% magnesium also tended to be lower than those of rats fed diets containing 0.025% and 0.05% magnesium. These results suggested that dietary magnesium and calcium competed with each other in intestinal absorption; therefore 0.05% dietary magnesium level was preferable compared with 0.15% dietary magnesium if the diet contained 0.5% calcium. On the other hand, the amounts of femoral magnesium of rats fed diets containing 0.15% magnesium were significantly higher than those of rats fed diets containing 0.025% magnesium, and the femoral breaking energy of rats fed diets containing 0.15% magnesium was significantly higher than that of rats fed diets containing 0.025% magnesium. These results also suggested that magnesium might have an effect on bone metabolism other than calcium absorption. (C) 1999 Elsevier Science Inc.