One idea that’s been floating around the diabetes research community for some time is that vitamin D might be helpful in lowering a person’s chance of developing type 2 diabetes. A new study, however, has shown that for the great majority of people it probably isn’t.
The research, The New England Journal of Medicine, was based on findings from what’s called the Vitamin D and Type 2 Diabetes (D2d) trial. The study was comprised of 2423 individuals from 22 cities in the United States, all of whom had been diagnosed as having prediabetes. There were roughly equal numbers of men and women and the average age was 60. The subjects were separated into two groups — one group received a daily dose of 4000 IU (International Units) of vitamin D and the other received a placebo (an inactive substance). According to lead investigator Anastassios G. Pittas, MD, “We did the D2d study to test the hypothesis that vitamin D supplementation lowers risk for diabetes in people who are at risk for diabetes.”
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The participants in the study were followed up for 2 1/2 years, during which time they were given blood tests every six months. Over the course of the study, 293 people in the vitamin D group and 323 in the placebo group developed new-onset diabetes. Dr. Pittas concluded that “the effect was not statistically significant.”
However, there was one encouraging finding. About 17% of the subjects were found to have insufficient levels of vitamin D and 4% were found to be vitamin D deficient. As Dr. Pittas explained, “We looked at a small subgroup of the cohort with vitamin D deficiency…. Among those participants, there was a 62% reduction in diabetes risk.” In other words, although vitamin D doesn’t appear to prevent diabetes in people with sufficient vitamin D levels, it likely reduces the risk in people with insufficient levels.
Dr. Pittas pointed out that some other large-scale studies on the relationship between vitamin D and diabetes are being developed and the results should throw more light on the question. But in the meantime, because the researchers found no safety issues with a daily dose of 4000 IU of vitamin D, they advised that physicians recommend vitamin D supplementation for patients who are both at risk for diabetes and whose vitamin D levels are low.
A freelance writer and editor based in the Chicago area, Gustaitis has a degree in journalism from Columbia University.