Study: Vitamin D May Cut Risk Of Type 1 Diabetes

A new study by researchers at the Harvard School of Public Health adds to growing evidence that vitamin D plays a critical role in maintaining overall health.

The new government-funded study, published online in the American Journal of Epidemiology, suggests that a simple intervention — having adequate levels of vitamin D during young adulthood — may cut the risk of developing adult-onset, type 1 diabetes by as much as 50 percent.



Here’s some of the Harvard news release:

This study provides the strongest findings to date to suggest that vitamin D may be protective against type 1 diabetes.

In type 1 diabetes (once called juvenile-onset or insulin-dependent diabetes), the body’s immune system attacks and permanently disables the insulin-making cells in the pancreas. About 5% of the estimated 25.8 million people in the United States with diabetes have type 1, according to the American Diabetes Association. Although it often starts in childhood, about 60% of type 1 diabetes cases occur after age 20.

Previous studies have suggested that a shortage of vitamin D might boost type 1 diabetes risk, although those studies mostly examined the link between vitamin D levels in pregnancy or childhood and the risk of type 1 diabetes in children. Other research, in young adults, uncovered an association between high vitamin D levels and a lowered risk of multiple sclerosis—an autoimmune disease genetically and epidemiologically related to type 1 diabetes—suggesting that inadequate vitamin D in adulthood may be an important risk factor for autoimmune diseases in general…

The researchers conducted a prospective case-control study of U.S. military personnel on active duty, using blood samples from the Department of Defense Serum Repository, which contains more than 40 million samples collected from 8 million military personnel since the mid-1980s. Identifying 310 individuals diagnosed with type 1 diabetes between 1997 and 2009, the team examined blood samples taken before onset of the disease, and compared the samples with those of 613 people in a control group.

The researchers found that white, non-Hispanic, healthy young adults with higher serum levels (>75 nmol/L) of vitamin D had about half the risk of developing type 1 diabetes than those with the lowest levels of vitamin D (<75 nmol/L). Although the researchers found no significant association among Hispanics and blacks, the authors said this may be due to the small number of individuals in these groups.

“The risk of type 1 diabetes appears to be increased even at vitamin D levels that are commonly regarded as normal, suggesting that a substantial proportion of the population could benefit from increased vitamin D intake,” said Alberto Ascherio, professor of epidemiology and nutrition at HSPH, the study’s senior author…

Worldwide, an estimated 1 billion people have inadequate levels of vitamin D in their blood, and deficiencies can be found in all ethnicities and age groups. While sun exposure is an excellent source of vitamin D, sunscreen, clothing, skin pigmentation, and winter months reduce vitamin D production. Food tends to be a poor source of vitamin D, with “good” sources, such as salmon and fortified milk, containing 400IU or less per serving. “Whereas it is premature to recommend universal use of vitamin D supplements for prevention of type 1 diabetes, the possibility that many cases could be prevented by supplementation with 1,000-4,000 IU/day, which is largely considered safe, is enticing,” the authors said.

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  • Reasonable?

    Vitamin D is hard to dose orally.
    We were meant to take vitamin D in via the sun.
    There was a classic association of Type 1 Diabetes and MS with Northern European ancestery. It could be environmental.
    We were designed for more sunlight than our environment provides.

  • David C. Holzman

    Here is an old, but exceptionally comprehensive article on vit D from the journal of the National Institute of Env’tal Health Sciences:

  • Christine

    Am curious whether 1,000-4,000 IU/day is safe for young children. Would be a helpful to know given most kids who get type 1 do so between the ages of 10-14 which would mean supplements would need to be given to kids under 10 to have any effect, no?

    • David C. Holzman

      I’m not sure what the optimum dose for kids is, but kids under 10 should definitely be getting supplements, probably somewhere in that 1,000-4,000 range unless they are spending time in the sun sans sunscreen where it’s high enough in the sky that their shadow is shorter than their height. People with low blood levels of Vit D are more likely to get infectious disease, cancer, and autoimmune disease. Based on measurements of levels in aboriginal populations in the tropics the Vit. D Counsel recommends a minimum of about 45 ng/ml. The 75 nmol/L in the article is equivalent to 30 ng/ml.

      I’ve had my blood level taken twice. In August a few years ago, it was around 50ng/ml, with no supplements, but running shirtless every day. In December of the same year, it was also ~50ng/ml, and I was taking 3,000-4,000 IU/day.

      At Boston’s latitude, the sun is too low in the sky to catalyze vit D production in the skin from roughly end of September or early October until late March.