Effects of encapsulated magnesium on growth and bone mineral concentrations in weanling rats

Abstract

The effect of magnesium oxide (MgO) encapsulated (E) with a modified cellulose (Ethocel) on growth and bone minerals was assessed in weanling rats. Ethocel encapsulated Mg was added to bread flour at 10 or 30% of RDA/serving (80 mg/100g or 240 mg/100g dry bread). Bread meal, previously supplemented with Mg, was the sole source of Mg in the diet based on AIN93G. Male Sprague-Dawley rats, 26 d old, 8/group, were given either control diet: AIN93G or bread based diets: Mg10E, Mg30E and Mg30N (nonencapsulated) for 4 weeks. Food intake and weight gain of rats fed Mg10E and 30E diets declined 22 and 45%, respectively (P≤0.05). The decline in liver, femur and tibia weights was consistent with decreased food intake and weight gain. Plasma Mg remained unaltered, while plasma Ca concentrations were 14 and 26% lower than the control in the Mg30E and Mg30N groups (P≤0.05). Femur Mg levels were similar to control, but tibia Mg concentrations were reduced by an average of 24% in Mg10E and Mg30E groups and significantly (43%) in the Mg30N group. There was a significant reduction in tibia Ca in the Mg30N group of about 43%; the decline in femur and tibia calcium in the other two bread groups was less significant. The data suggest that encapsulation of MgO did not alter the bioavailability of Mg; it minimized the adverse effects of supplemental Mg on calcium homeostasis.