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Vitamin D Does Not Prevent Type 2 Diabetes in People at High Risk
June 10, 2019

Taking a daily vitamin D supplement does not prevent type 2 diabetes in adults at high risk of developing the disease, according to a study published in The New England Journal of Medicine and presented at the 79th Annual Scientific Sessions of the American Diabetes Association (ADA).

The Vitamin D and Type 2 Diabetes (D2d) enrolled 2,423 adults aged 30 years or older at 22 sites across the United States and randomised participants to take cholecalciferol 4,000 IU/day or placebo. All participants had their vitamin D levels measured at the start of the study, at which time about 80% had vitamin D levels considered sufficient by US nutritional standards.

The study screened participants every 3 to 6 months for an average of 2.5 years to determine if diabetes had developed. The researchers then compared the number of people in each of the 2 study groups that had progressed to type 2 diabetes. At the end of the study, 293 out of 1,211 (24.2%) participants in the vitamin D group developed diabetes compared with 323 out of 1,212 (26.7%) in the placebo group -- a difference that did not reach statistical significance. The study was designed to detect a risk reduction of ≥25%.

D2d enrolled a diverse group of participants with a range of physical characteristics, including sex, age, and body mass index, as well as racial and ethnic diversity. This representation helps ensure that the study findings could be widely applicable to people at high risk for developing type 2 diabetes.

“In addition to the study’s size, one of its major strengths is the diversity of its participants, which enabled us to examine the effect of vitamin D across a large variety of people,” said lead author Anastassios G. Pittas, MD, Tufts Medical Center, Boston, Massachusetts. “When the study ended, we found no meaningful difference between the two groups regardless of age, sex, race or ethnicity.”

The researchers also evaluated the safety of taking daily high-dose vitamin D and found no difference in the number and frequency of predicted side effects, such as high blood calcium levels and kidney stones, when compared with patients in the placebo group.

Reference: https://www.nejm.org/doi/full/10.1056/NEJMoa1900906

SOURCE: National Institutes of Health