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Aug 27, 2023

Vitamin D Might Help Prevent Type 2 Diabetes

| June 2, 2023 People who have prediabetes might be able to ward off type 2

| June 2, 2023

People who have prediabetes might be able to ward off type 2 diabetes by consuming more vitamin D, according to a new study published in the Annals of Internal Medicine. The authors conducted what they called a "systematic review and meta-analysis" of previously published studies and reported that people with prediabetes could lower their risk of developing type 2 diabetes by 15% by supplementing their diets with vitamin D.

Prediabetes, a condition in which a person's blood sugar levels are higher than normal but not high enough to qualify as actual diabetes, is common. According to the U.S. Centers for Disease Control (CDC), some 96 million American adults — more than one in three — have prediabetes, and the great majority of them (80%) don't even know it. These large numbers explain why it's imperative for medical researchers to study possible strategies for preventing prediabetes from turning into actual type 2 diabetes.

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The authors of the new paper noted that some earlier studies have reported an association between vitamin D, blood glucose levels, and risk for developing type 2 diabetes, but they said no previous studies had looked into whether vitamin D might lower the risk of getting type 2 diabetes in people with prediabetes. One of the authors of the newly published report, Anastassios G. Pittas, MD, chief of Endocrinology, Diabetes, and Metabolism at Tufts Medical Center, had led a study in 2019 that investigated whether subjects at high risk of developing type 2 diabetes (but not necessarily with prediabetes) might lower their chances of developing the disease if they took vitamin D supplements. In that study, the authors reported that supplementation did not result in a statistically lower risk than did a placebo (inactive treatment).

The review the researchers conducted was based on trials that measured the effect of vitamin D administered orally compared to placebo in adults with prediabetes. They eventually identified three suitable randomized trials that included 4,190 people. Of these, about half of the subjects (51%) were white and 44% were women, while the average age was 61. The main thrust of their research was how long it took for people to develop actual type 2 diabetes, but they also assessed safety and whether any of the subjects returned to "normal" glucose regulation.

The researchers found that, over a median follow-up of three years, one-quarter of the subjects in the placebo groups developed new cases of type 2 diabetes, while the percentage of new cases in the vitamin D groups was lower (22.7%). After adjustments, the authors reported that vitamin D lowered diabetes risk by 15%. In addition, they found that the percentage of subjects in the vitamin D groups who regressed to normal glucose regulation was nearly one-third (30%). As for safety, they reported no difference between the groups in "adverse events," which included kidney stones, abnormally high blood calcium levels (hypercalcemia), and abnormally high levels of calcium in the urine (hypercalciuria).

This seemingly good news, however, did come with some qualifications. For one, in order for the diabetes prevention effect to take place, the vitamin D dosage might be, as the authors put it, "near and possibly above" earlier recommendations from the Institute of Medicine. There's a difference between supplementation and therapy, and very high doses of vitamin D might be harmful. As the researchers wrote, "…the benefit and safety of vitamin D are population-specific, and the balance of benefit and safety require constant assessment as evidence evolves." Secondly, other diabetes prevention strategies have an even stronger preventive effect. For instance, "intensive lifestyle modification" cuts risk by 58% and using the oral diabetes medication metformin lowers risk by 31%. Finally, most nutritional supplements are not regulated the way pharmaceutical drugs are.

Want to learn more about vitamin D? Read "Vitamin D: Making Sure You Get Enough."

Want to learn more about prediabetes? Read "What Is Prediabetes? Symptoms, Treatment, and More," "Prediabetes Treatment" and "Diabetes Prevention: Eat to Beat Diabetes."

Disclaimer of Medical Advice: Statements and opinions expressed on this Web site are those of the authors and not necessarily those of the publishers or advertisers. The information, which comes from qualified medical writers, does not constitute medical advice or recommendation of any kind, and you should not rely on any information contained in such posts or comments to replace consultations with your qualified health care professionals to meet your individual needs.

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