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Adults With Prediabetes

February 7, 2023

Researchers from the Division of Endocrinology at Tufts Medical Center found that vitamin D was effective in lowering the risk for developing diabetes in adults with prediabetes.

In a new study, researchers from the Division of Endocrinology at Tufts Medical Center found that vitamin D was effective in lowering the risk for developing diabetes in adults with prediabetes

Taso Pittas, MD

Vitamin D is a fat-soluble vitamin that is naturally present in a few foods, added to others and available as a dietary supplement or by prescription at higher doses. It is also produced by the body when ultraviolet rays from sunlight strike the skin. Vitamin D has many functions in the body, including a role in insulin secretion and glucose metabolism. Observational studies have found an association between having a low level of vitamin D in the blood and a high risk for developing diabetes.

Authors of the study set out to determine whether giving vitamin D to people who were at high risk for diabetes could reduce the risk of progressing to diabetes. The authors searched three databases for trials that specifically focused on comparing the use of vitamin D versus placebo in adults with prediabetes for diabetes prevention, and found three vitamin D and diabetes prevention trials.

"In these trials, including the D2d study which our team conducted, vitamin D reduced the risk for diabetes, but the reported risk reduction was not statistically significant in any trial because the percentages were smaller than each trial was powered to detect," said Anastassios G. Pittas, MD, MS, Chief of the Division of Endocrinology, Diabetes and Metabolism at Tufts Medical Center and the lead author of the study. "To increase the statistical power to detect an effect, Drs. Kawahara and Jorde (who led the Tromsø and DPVD trials, respectively) and I combined individual participant data from the three trials in a meta-analysis."

After checking the quality of the data, the researchers harmonized the data into standard units with unified coding. They then used statistical approaches to compare the rates of diabetes in patients who received vitamin D compared with those who received placebo.

After following participants for an average of three years, new-onset diabetes occurred in 22.7% of adults who received vitamin D and 25% of those who received a placebo. This translates to vitamin D reducing the risk of developing diabetes by 15%. About 30 adults with prediabetes would need to be treated with vitamin D to prevent 1 person from developing diabetes.

"These results indicate a modest benefit of vitamin D in lowering diabetes risk in adults with prediabetes," said Dr. Pittas. "However, there are still some important unknowns. Specifically, we do not know the optimal vitamin D dose or formulation, and whether we should be aiming for a specific blood vitamin D level to maximize benefit in this population, with little or no risk of any side effects. Additional research will need to be done to answer these important questions."

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