Women with high intakes of vitamin D and calcium appear to have a lower risk of developing type 2 diabetes, according to Boston-based researchers.

Dr. Anastassios G. Pittas, of Tufts-New England Medical Center and colleagues looked at data on 83,779 women enrolled in the Nurses’ Health Study. The women had no history of diabetes, cardiovascular disease or cancer when they enrolled in the study. Vitamin D and calcium intake from foods and from supplements were evaluated every 2 to 4 years.

A total of 4843 new cases of diabetes were documented over 20 years of follow-up.

“Based on the latest guidelines set by the Institute of Medicine, only 3% of women in our cohort had adequate vitamin D intake, and only 24% had adequate calcium intake,” Pittas’s group reports in the medical journal Diabetes Care.

Total vitamin D intake was not significantly associated with type 2 diabetes, but there was a difference when it came to vitamin D supplements. The team saw a 13 percent lower risk of diabetes among women in the highest versus the lowest category of vitamin D intake from supplements.

Women with the highest total calcium intake had a 21 percent lower risk of diabetes than those with the lowest intake. In this case, the source of calcium didn’t make much difference: the risk was 18 percent lower among women in the highest versus the lowest category of calcium intake from supplements.

Overall, the lowest risk of diabetes was observed among women with the highest combined intakes of calcium and vitamin D compared with those with the lowest.

The researchers say their findings could have “important public health implications,” because interventions to raise both vitamin D and calcium intake “can be implemented easily and inexpensively to prevent type 2 diabetes.”

SOURCE: Diabetes Care, March 2006.