Tufts Medical Center gets $40 million to see if vitamin D can prevent diabetes

A Tufts Medical Center researcher has received a grant of more than $40 million from the National Institutes of Health to head a multi-center clinical trial aimed at determining whether taking vitamin D supplements can help prevent type 2 diabetes in those at increased risk, Tufts announced Monday.

Americans spend $425 million every year on vitamin D supplements to protect against an array of health conditions—from cancer to multiple sclerosis to heart disease—but there’s a lack of evidence from clinical trials that the supplement does anything beyond preventing bone loss and falls in the elderly.

“The latest vitamin D studies have had some disappointing results,” said Dr. Anastassios Pittas, the Tufts researcher heading the study. But there’s reason to suspect vitamin D may have some beneficial effects in terms of how the body’s cells respond to the hormone insulin, which is responsible for regulating blood sugar.

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Pittas has conducted smaller studies over the past decade that found that those at increased diabetes risk who took vitamin D supplements had improved blood sugar levels. “There is a lot of preliminary evidence that this might help, but we expect to get more definitive answers in this new study.”

He and his colleagues will recruit 2,400 patients over age 30 at 20 medical centers—Tufts is the only one in Boston. The participaants will be randomly assigned to take vitamin D3 (a form of the vitamin that’s most easily absorbed by the body) or a placebo. Participants must have pre-diabetes—also known as insulin resistance—confirmed by blood tests that will be administered by the resesearchers. About 10 percent of those with pre-diabetes progress to full-blown diabetes each year, and the study will measure whether that rate can be reduced by supplementation.

Those provided with vitamin D supplements instead of sugar pills will get a hefty daily dose—4,000 international units—which is far higher than the 600 to 800 IU recommended by the Institute of Medicine in their latest guidelines.

“Deciding the dose was quite a challenge,” Pittas said. Those already taking vitamin D supplements won’t have to stop if they participate in the trial, and most people on the supplements take about 1,000 IU a day. “We wanted to give a dose that is still considered safe but is also high enough to differentiate from those on placebo who may still be taking a supplement.”

Recruitment for the study opened on Monday, and those interested in participating can call 617-636-2843, e-mail d2dtufts@tuftsmedicalcenter.org, or visit the study’s website at www.D2dstudy.org.