Impaired glucose tolerance in vitamin D deficiency can be corrected by calcium

Vitamin D-3, via its active metabolite 1 alpha,25-dihydroxyvitamin D-3, helps maintain normal calcium levels in the body Apart from the maintenance of calcium homeostasis, the active form of vitamin D-3 is now known to be involved in a number of other functions including that of pancreatic beta cells. Low serum insulin levels and impaired glucose tolerance in a vitamin D-deficient state have been reported in experimental animals Hypocalcemia is a major consequence of vitamin D deficiency Whether the impairment observed is due to vitamin D deficiency per se or is secondary to low calcium is still a matter of controversy. The present study was conducted to delineate the roles of vitamin D and calcium in glucose intolerance associated with vitamin D deficiency in vivo. It was found that supplementation with either vitamin D-3 or high calcium alone to vitamin D-deficient rats could correct the defects. In addition, insulin sensitivity was found to be enhanced in the vitamin D-deficient group compared with vitamin D control or calcium-supplemented groups. Hence the present study demonstrates that calcium per se in the absence of vitamin D increases insulin secreation and normalizes intolerance to glucose seen in vitamin D deficiency. (C) Elsevier Science Inc. 2000. All rights reserved.