Can vitamin D reduce the risk of full-blown diabetes in people with prediabetes?

This study looked at the effect of vitamin D levels in reducing the risk of full-blown diabetes in people with prediabetes. They found that having high levels of vitamin D reduced the risk of developing diabetes. 

Prediabetes means a higher than normal blood glucose (sugar) level. However, not high enough to be considered diabetes. People with prediabetes have a high risk of developing full-blown diabetes unless they make changes in their diet and lifestyle. Research shows that people who have low vitamin D levels are at increased risk of developing diabetes. However, it is not clear what level of vitamin D is best for preventing diabetes in people with prediabetes.

This study involved 2,158 patients with prediabetes. They were divided into 2 groups. Group 1 received high dose vitamin D supplements (100µg or 4,000 units) while group 2 received a placebo. Participants were followed for an average of 2.5 years. Vitamin D levels were checked at the start of the study and every year after. Three levels of vitamin D were compared. Normal levels were considered 54-99 nmol/L, high levels were 100-124 nmol/L, and very high levels were above 125nmol/L. 

70% of participants receiving high dose vitamin D maintained high or very high vitamin D levels. Those with high vitamin D levels were 52% less likely to develop diabetes than those with normal levels.  Those with very high vitamin D levels were 71% less likely to develop diabetes. For each increase in vitamin D levels of 25nmol/L, the risk of developing diabetes decreased by 25% in those assigned to group 1 and by 10% in those in group 2.

The authors concluded that maintaining consistently high levels of vitamin D (higher than the normal level) may help protect against diabetes in people with prediabetes. 

This study did not evaluate the safety of maintaining high levels of vitamin D. More research is needed to ensure there are no safety issues with maintaining very high levels of vitamin D.

Speak to your physician about the use of high dose vitamin D supplements to reduce your risk of diabetes.