Is Vitamin D Supplementation Effective in Prevention of Type 2 Diabetes

For a long period of time, vitamin D has been known to be effective in preventing type 2 diabetes. However, research must be able to prove that.

Diabetes is one of the major health challenges faced by the majority of the worldwide population. The numbers continue to grow and affect individuals of all ages. Those at high risk for type 2 diabetes are overweight/ obese and have an impaired glucose tolerance and elevated fasting blood glucose levels. In order to control and prevent diabetes, one must adjust their dietary lifestyles. However, keeping up with lifestyle changes may be challenging. Therefore, there are convenient approaches that can be implemented that will aid in reinforcing lifestyle changes in order to to lower the risk of type 2 diabetes in persons with prediabetes.

Over the years, there was indication that low vitamin D levels may contribute to the onset of diabetes. Furthermore, as of recently, several trials testing the effect of vitamin D supplementation to reduce the rate of progression to diabetes in people with prediabetes have been completed to determine whether vitamin D supplementation does or does not play a role in diabetes prevention. Lack of adequate levels of vitamin D are said to increase insulin resistance.

It is crucial to assess vitamin D status objectively when necessary by laboratory blood testing of the serum 25(OH)D levels. Type 2 diabetes patients are said to benefit from improving their vitamin D status in regards to their glucose metabolism and decreased mortality risk. Those patients diagnosed with insulin resistance who are vitamin D deficient should be treated with an appropriate amount of vitamin D to achieve circulating levels of 25(OH)D of 40–60 ng/mL (Grober & Holick, 2019).

A randomized double-blind placebo-controlled study by Lemieux et al., 96 subjects with prediabetes, mostly those who were vitamin D deficient, were given daily doses of 5000 IU vitamin D3 or placebo for 6 months. In the initial stage of the study, the mean 25(OH)D level was 20.4 ng/mL. After 6 months, the 25(OH)D levels in the active treatment group had risen significantly, from 20.4 ng/mL to 51 ng/mL compared to the placebo group. Conversely  to the placebo group, the vitamin D supplemented patients showed a significant beneficial effect on beta cell function and insulin sensitivity after 6 months. According to the investigators of the study, vitamin D supplementation in persons with prediabetes and an inadequate vitamin D status  can improve insulin sensitivity.

In conclusion, it may be rationa to recommend appropriate vitamin D supplementation along the guidelines recommended by the Endocrine Society. Recommendations of daily doses are as follows: 400–1000 IUs, 600–1000 IUs, and 1500–2000 IUs of vitamin D to maintain blood levels of 25(OH)D >30 ng/mL.

Gröber U, Holick MF. Diabetes Prevention: Vitamin D Supplementation May Not Provide Any Protection If There Is No Evidence of Deficiency! Nutrients. 2019 Nov 4;11(11):2651. doi: 10.3390/nu11112651. PMID: 31689953; PMCID: PMC6893410.

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