Vitamin D and calcium supplementation along with diet and exercise may prevent type 2 diabetes in prediabetic individuals who have insufficient vitamin D in their bodies, a study from India suggests. The results were presented Saturday at the joint meeting of the International Society of Endocrinology and the Endocrine Society in Chicago.

Vitamin D deficiency has been linked to prediabetes, which is a blood glucose, or sugar, level that is too high but not high enough to be considered diabetes. It is unclear, however, if bringing low vitamin D blood levels to normal through supplementation will affect progression to diabetes.

In the new study, every unit increase in vitamin D level after supplementation of the vitamin decreased the risk of progression to diabetes by 8%, the authors reported.

“Without healthy lifestyle changes, nothing works to prevent diabetes in at-risk individuals,” said the lead author, Deep Dutta, MD, DM, a research officer at the Institute of Postgraduate Medical Education & Research and Seth Sukhlal Karnani Memorial Hospital in Calcutta, India. “However, our results are encouraging because the addition of vitamin D and calcium supplements is easy and low in cost.”

“If our results are confirmed in a large multicenter trial vitamin D supplementation would provide us with a new tool in the armamentarium of diabetes prevention strategies," Dutta said.


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The West Bengal chapter of the Research Society for the Study of Diabetes in India funded this study. Of 170 individuals with prediabetes who had not taken vitamin D supplements in the past six months, 125 had vitamin D deficiency or insufficiency, which the researchers defined as a vitamin D blood level (25-hydroxyvitamin D) of 30 nanograms per milliliter (ng/mL) or less. These 125 study subjects were randomly assigned to one of two treatment groups. In the first group, 68 subjects received ready-to-mix, powdered vitamin D3 (cholecalciferol, D-Rise sachets, USV Ltd., Mumbai, India) at a dose of 60,000 IU once weekly for eight weeks and then monthly. They also received a daily 1,250-milligram calcium carbonate tablet.

The other group of 57 subjects received only calcium supplements. Both groups received advice to eat a healthy, calorie-appropriate diet and to engage in brisk exercise for 30 minutes each day.

The researchers analyzed results for subjects who had at least a year of follow-up tests. After an average of nearly two years and four months’ follow-up, only six of 55 subjects (10.9%) in the group that received vitamin D plus calcium supplementation had become diabetic, whereas diabetes developed in 13 of 49 individuals (26.5 percent) in the calcium-alone group. Blood sugar levels reportedly became normal in about twice as many people in the vitamin D group as in the group that did not get vitamin D supplementation: 23 of 55 subjects versus 10 of 49 subjects, respectively (41.8% versus 20.4%).

At the end of the study, those who received vitamin D supplementation had much higher vitamin D levels in the blood and lower fasting blood glucose levels compared with the other group. Every unit (1 ng/mL) increase in vitamin D in the body was associated with a 5.4% increased chance of reversal to normal blood sugar levels, Dutta reported.

He said the greater reversal to normal blood sugar in the vitamin D group presumably occurred through improvements in their insulin resistance and inflammation.