Magnesium-deficient diet-induced reduction in protein utilization in rats is reversed by dietary magnesium supplementation.

We investigated the effect of dietary magnesium (Mg) level on protein utilization in rats. Male Wistar rats were fed a control diet (control group) and a Mg-deficient diet (Mg-deficient group) for 28 days. After 28 days, the diet of half of the Mg-deficient group (recovery group) was changed from the Mg-deficient diet to the control diet for either 7 or 14 days. After 28 days, final body weight, weight gain and food efficiency were significantly decreased due to the Mg-deficient diet. Apparent Mg absorption, Mg retention and serum Mg levels were also significantly decreased due to the Mg-deficient diet. Furthermore, the Mg-deficient group showed a significant increase in urinary nitrogen (N) excretion and significant decreases in N retention and serum albumin level. At day 7 and 14 after changing the Mg-deficient diet to the control diet, apparent Mg absorption, Mg retention and serum Mg levels were significantly increased in the recovery group as compared with those in the Mg-deficient group. However, with regard to final body weight, weight gain and food efficiency, no significant differences were observed between the Mg-deficient group and the recovery group. At day 14 after changing the diet, urinary N excretion was significantly decreased and N retention was significantly increased in the recovery group as compared with the Mg-deficient group. At day 7 and 14 after changing the diet, the serum albumin level was also significantly increased in the recovery group as compared with that in the Mg-deficient group. These results suggest that: 1) the Mg-deficient diet depresses protein utilization; 2) the Mg-deficient diet-induced impairment of protein utilization is reversed by dietary Mg supplementation; and 3) the Mg-deficient diet-induced growth retardation is not completely reversed after 14 days of Mg supplementation.