In a new study from the National Institutes of Health, researchers found that taking a daily vitamin D supplement does not prevent type 2 diabetes in people at high risk.
Currently, more than 50% of adults in the U.S. take nutritional supplements, and the use of vitamin D has increased over the last 20 years.
The team tested 2,423 adults aged 30 or older and the research was done at 22 sites across the United States.
The aim was to directly examine if daily vitamin D supplementation helps keep people at high risk for type 2 diabetes from developing the disease.
In the study, the participants took either 4,000 International Units (IU) of the D3 (cholecalciferol) form of vitamin D or a placebo pill daily.
All study participants had their vitamin D levels measured at the start of the study.
At that time, about 80% of participants had vitamin D levels considered sufficient by U.S. nutritional standards.
The team tested these participants every three to six months for an average of 2.5 years to determine if diabetes had developed.
At the end of the study, about 24% of participants in the vitamin D group developed diabetes compared to 27% in the placebo group.
The difference was too small to be significant.
The team also found that taking 4,000 units of vitamin D daily, which is greater than the average daily recommended dose of 600-800 IUs a day, is safe.
This high amount of vitamin D doesn’t lead to higher blood calcium levels and kidney stones compared with placebo.
The researchers suggest that lifestyle change or the drug metformin remain effective methods to prevent type 2 diabetes.
They will continue to search for new ways to prevent the disease in their future work.
The lead author of the study is Anastassios G. Pittas, M.D., principal investigator from Tufts Medical Center.
The study is published in the New England Journal of Medicine.
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