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A new scientific analysis finds that people with prediabetes who take vitamin D have a lower risk of developing type 2 diabetes.
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Previous research has found a similar link.
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Endocrinologists and dietitians explain the link.
More than one in three American adults has prediabetes, a condition where blood sugar levels are higher than normal, but not high enough to be diagnosed as type 2 diabetes. While prediabetes and type 2 diabetes are complicated conditions, new research suggests taking a vitamin D supplement may help lower blood sugar in certain groups.
The study, published in the Journal of the Endocrine Society, analyzed data from 10 clinical trials involving nearly 4,500 people with prediabetes. The researchers discovered that 18.5% of study participants who took vitamin D reached normal blood sugar levels, compared to 14% who took a placebo. In all of the trials, the data showed that people with prediabetes who took vitamin D were more likely to develop normal blood sugar levels.
Meet the experts: Sylvia Christakos, Ph.D., is a vitamin D researcher and professor of microbiology at Rutgers New Jersey Medical School; Jessica Cording, R.D., is author of The Little Book of Game Changers; David Cutler, M.D., is a family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA; Ankit Shah, M.D., assistant professor in the Division of Endocrinology, Metabolism, and Nutrition at Rutgers – Robert Wood Johnson Medical School; Anastassios Pittas, M.D., is a study co-author and a professor of medicine at Tufts University School of Medicine
The connection between vitamin D and blood sugar management seems random, but doctors say there is something to this. But experts warn this does not mean you should forego a regimen or treatment recommended by your doctor in favor of a supplement. Here’s what the research found, and what it may mean.
What is vitamin D?
Vitamin D is a fat-soluble vitamin, per the National Institutes of Health (NIH). Also known as calciferol, the vitamin helps your gut’s absorption of calcium. If you don’t have enough vitamin D, your bones may become thin and brittle.
But vitamin D plays many roles in the body, including reducing inflammation and supporting immune function and blood sugar metabolism, according to the NIH.
Vitamin D is produced by your body when your skin is exposed to the sun’s rays, and it’s also found in some foods, like certain fatty fish, mushrooms, and fortified milk and cereal, says Jessica Cording, R.D., author of The Little Book of Game Changers.
Why might vitamin D help with blood sugar management?
That’s still being explored, although this isn’t the first time vitamin D has been linked with managing diabetes. A scientific analysis published in the Annals of Internal Medicine in 2023 analyzed three clinical trials that studied the impact of vitamin D supplementation on people with prediabetes. During a three-year follow-up, the researchers discovered that 22.7% of participants who took vitamin D developed type 2 diabetes, compared to 25% of those who took a placebo.
The differences aren’t massive—meaning, taking a vitamin D supplement isn’t a guarantee that you’ll avoid developing type 2 diabetes—but many experts agree that there does seem to be something here.
One theory behind this link is that vitamin D impacts glycemic control, which is your body’s ability to manage your blood sugar, Cording says. “Vitamin D is actually a hormone,” Cording points out. Having healthy levels of vitamin D may in theory help regulate other hormones in the body, helping to support the function of your endocrine system. (Type 2 diabetes impacts the endocrine system, which regulates glucose, a.k.a. blood sugar, levels in the blood, Cording explains.)
Vitamin D is also linked to a lower risk of insulin resistance, which is when the body is unable to respond to or use the hormone insulin. Insulin helps to escort sugar to your cells, where it’s used for energy. Insulin resistance is often seen as a part of prediabetes and a precursor for type 2 diabetes.
“Additionally, vitamin D may have an anti-inflammatory effect, and inflammation is a known risk factor for developing diabetes,” says Ankit Shah, M.D., assistant professor in the Division of Endocrinology, Metabolism, and Nutrition at Rutgers, Robert Wood Johnson Medical School.
But there are still a lot of unknowns here. “The mechanisms involved in potential helpful effects of vitamin D in lowering the risk for type 2 diabetes at this time have not been well defined,” says Sylvia Christakos, Ph.D., a vitamin D researcher and professor of microbiology at Rutgers New Jersey Medical School.
However, she points out that data suggest that people with low vitamin D levels also seem to have impaired pancreatic beta cell function and insulin resistance. Both of those are linked to the development of type 2 diabetes.
It’s also entirely possible that there’s nothing to this link, says David Cutler, M.D., a family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA. “It’s very easy to find studies that show associations,” he says. “You have to accept that many studies that were done showed no association and never came to light.”
Should I use vitamin D to manage blood sugar?
As of right now, there’s no official recommendation on using vitamin D to manage blood sugar in people with prediabetes. However, Christakos recommends having your vitamin D levels tested if you’re at high risk of developing type 2 diabetes. If you’re low, your doctor may recommend that you take a vitamin D supplement to support several areas of your health, not just your blood sugar.
Dr. Shah agrees. “While vitamin D deficiency and diabetes are two separate issues that have different treatment strategies, there might be a benefit such that treating one issue may have positive spillover effects on the other,” he says.
If your doctor says you could benefit from taking a vitamin D supplement, it’s important to have the right expectations for what this could do for you, says Anastassios Pittas, M.D., study co-author and a professor of medicine at Tufts University School of Medicine.
“Vitamin D should be viewed as part of an overall diabetes prevention plan, not a stand-alone solution,” he says. “In the vitamin D and diabetes prevention trials, participants took an average of about 4,000 IU of vitamin D daily. That dose would be a good starting point.” He says some people may need a bit less or more, depending on their lifestyle and size. Again, it’s important to consult your doctor before adding a supplement to your routine.
But Cording says it’s important to keep in mind that you can overdo it with vitamin D. So, you don’t want to put yourself on this vitamin without talking to a healthcare professional first. “Taking too much vitamin D can lead to vitamin D toxicity,” she points out. That can cause your body to absorb too much calcium, raising your risk of kidney stones and constipation. In extreme cases, it may even lead to heart rhythm issues, kidney failure, and death, per the NIH.
How to lower type 2 diabetes risk
Dr. Shah stresses that you’re not doomed to develop type 2 diabetes if you’ve been diagnosed with prediabetes. “Having prediabetes puts you at risk for developing overt type 2 diabetes, but it does not have to be a foregone conclusion,” he says. “One can prevent, or at least delay, this progression by employing multiple well-known strategies.”
That means focusing on eating a low-glycemic diet, doing your best to manage your weight (as this may impact insulin resistance), and exercising regularly, Dr. Cutler says. “These are all proven to both prevent type 2 diabetes and help with blood sugar control,” he says. Dr. Shah also recommends trying to reduce your stress levels and aiming to get at least seven hours of sleep a night.
Ultimately, it’s important to have a conversation with your healthcare provider if you’ve been diagnosed with prediabetes. They should be able to give you personalized guidance on next steps.
Dietary supplements are products intended to supplement the diet. They are not medicines and are not intended to treat, diagnose, mitigate, prevent, or cure diseases. Be cautious about taking dietary supplements if you are pregnant or nursing. Also, be careful about giving supplements to a child, unless recommended by their healthcare provider.
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