Study: Vitamin D May Delay or Prevent Diabetes in People with Specific Gene Variations

More than two in five adults in the United States—over 115 million people—have prediabetes, a condition characterized by elevated blood sugar levels that often progresses to type 2 diabetes. A new study published in JAMA Network Open suggests that vitamin D supplementation may help delay or prevent diabetes progression, but only in individuals with specific genetic variations.

Key Findings: Vitamin D Reduces Diabetes Risk by 19% in Prediabetic Adults

The study analyzed data from the D2d study, a large, multi-site clinical trial that tested the effects of a daily high dose of vitamin D (4,000 units) versus a placebo in over 2,000 U.S. adults with prediabetes. While the original trial did not find a significant reduction in diabetes risk across all participants, further analysis revealed that those with certain genetic variations in the vitamin D receptor gene experienced a 19% lower risk of developing diabetes when taking vitamin D.

“But the D2d results raised an important question: Could vitamin D still benefit some people?” says Bess Dawson-Hughes, the study’s lead author and a senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. “Diabetes has so many serious complications that develop slowly over years. If we can delay the time period that an individual will spend living with diabetes, we can stop some of those harmful side effects or lessen their severity.”

How Vitamin D and Genetics Influence Diabetes Risk

Vitamin D circulates in the blood as 25-hydroxyvitamin D before being converted into its active form in the body. It then binds to the vitamin D receptor—a protein that helps cells respond to the vitamin. The pancreas’s insulin-producing cells contain vitamin D receptors, suggesting the vitamin may play a role in insulin release and blood sugar regulation.

For the new study, Dawson-Hughes and her team analyzed genetic data from 2,098 trial participants who had consented to DNA testing. They compared responses to vitamin D supplementation between two groups: those who benefited from the treatment and those who did not. The participants were then sorted into subgroups based on three common variations in the vitamin D receptor gene (ApaI): AA, AC, and CC.

Genetic Variations Determine Vitamin D’s Effectiveness

The analysis revealed that adults with the AA variation of the ApaI vitamin D receptor gene—approximately 30% of the study population—did not respond to daily high-dose vitamin D supplementation compared to the placebo group. However, adults with the AC or CC variations saw a significantly reduced risk of developing diabetes when taking vitamin D.

Implications for Personalized Diabetes Prevention

The findings suggest that vitamin D supplementation could be a targeted strategy for diabetes prevention in prediabetic individuals with specific genetic profiles. While the original D2d trial did not show a benefit for all participants, this new analysis highlights the potential for personalized medical care in diabetes prevention.

“If we can identify who is most likely to benefit from vitamin D supplementation, we may be able to delay or prevent the onset of diabetes for millions of Americans,” says Dawson-Hughes. “This could have a significant impact on reducing the long-term complications associated with diabetes.”