In the past, experimental studies suggested that calcium and vitamin D might reduce the risk of developing diabetes. In the April issue of Diabetes Care, the journal of the American Diabetes Association, investigators from the Women's Health Initiative Calcium/Vitamin D Trial reported that supplementation with calcium and vitamin D did not reduce the risk of developing diabetes.

This trial involved over 33,000 post-menopausal women who were randomly assigned to two groups - one group was treated with daily calcium plus vitamin D and the other group was given a daily placebo pill. Over an average follow-up time of 7 years, the investigators found that there was no significant difference in the number of new diabetes diagnoses between the two groups.

It may be that higher doses of vitamin D are needed to have an effect on diabetes risk. Still, as reported in the New England Journal of Medicine two years ago, the Women's Health Initiative did find that daily calcium and vitamin D supplements offer another type of benefit for healthy post-menopausal women - they offer small, but significant, improvements in preserving bone density and reducing hip fractures.