- Researchers are reporting that vitamin D supplementation can slightly reduce the risk of developing type 2 diabetes for people who have prediabetes.
- The risk reduction, however, was lower than other prevention strategies.
- Experts caution that people should be careful about how much vitamin D supplementation they take.
Supplementing with vitamin D might slightly lower the risk of type 2 diabetes for people with prediabetes, according to a study published today in Annals of Internal Medicine.
Researchers from the Tufts Medical Center in Massachusetts completed a review and meta-analysis of three clinical trials looking at the impact of vitamin D on the risk of developing type 2 diabetes.
The scientists looked for studies that included adults who took 4,000 IU of vitamin D supplements with a three-year follow-up.
They ended up with 2,097 participants who took vitamin D supplements and 2,093 who received a placebo.
During the trial dates:
- 475 people, or about 22%, in the vitamin D group received a new-onset diagnosis of diabetes
- 524 people, or about 25%, in the placebo group received a new-onset diagnosis of diabetes
The researchers extrapolated the numbers into a 15 percent decrease in the risk of developing type 2 diabetes for the participants taking vitamin D supplementation.
The researchers pointed out that vitamin D supplements could be an inexpensive way to delay type 2 diabetes in more than 10 million people worldwide with prediabetes.
Extrapolating their findings to account for the estimated
The researchers noted that a decrease of 15% is lower than other type 2 prevention strategies:
The supplements were generally well-tolerated.
Adverse events included kidney stones as well as high levels of calcium in the urine or blood, but the incidence rate for all was rare and there was no significant difference between the participant groups.
The researchers did not examine safety because the study parameters excluded some people who might be at risk for kidney problems.
The exclusions included children, pregnant or lactating women, hospitalized patients, those with end-stage renal disease, and HIV.
“Professional societies, which advise physicians about the benefits and harms of vitamin D therapy, have a duty of care to understand advice from government agencies, said Dr. Malachi McKenna of St. Vincents University Hospital in Ireland and Mary A.T. Flynn, Ph.D., of Brown University in Rhode Island in an accompanying editorial.
“They should promote population health recommendations about vitamin D intake requirements, thresholds, and safe limits,” the editorial writers noted. “There are important differences between supplementation and therapy. Vitamin D supplementation of 10 to 20 mcg (400 to 800 IU) daily can be applied safely at the population level to prevent skeletal and possibly nonskeletal disease. Very-high-dose vitamin D therapy might prevent type 2 diabetes in some patients but may also cause harm.”
The study did include people at high risk for type 2 diabetes, so the results cannot be generalized for the overall population.
After the trial ended, approximately 30% of the participants’ glucose levels returned to their levels before the study.
“These are interesting studies, and results should prompt further investigations in the form of large randomized trials,” said Dr. Rose Lin, an endocrinologist at Providence Saint John’s Health Center in California.
“The level of vitamin D associated with a nonsignificant reduction in diabetes is much higher than the generally recommended safe dosage, so recommendations for the general population to raise their vitamin D levels to this degree is not advised at this time,” she told Healthline.
Vitamin D is a nutrient that our body uses in multiple ways, according to the
- Helps the body absorb calcium to keep bones and keeps muscles healthy
- Assists nerves carrying messages to the brain
- Aids the immune system in fighting off bacteria and viruses
The daily recommended amount of vitamin D changes with age.
- Infants to 12 months should get 400 IU per day
- Adults aged 71 and older should get 800 IU per day
- The recommendation for everyone else is 600 IU per day
“One of the best ways to get a good dose of vitamin D is through a combination of sunlight and supplementation,” Dr. Mahmud Kara, the founder of Kara MD, told Healthline. “Sunlight offers a good natural source of vitamin D while a supplement can help supplement that source, especially for those that may live in less sunny areas.”
Kara suggests asking the following questions when looking for a supplement:
- Does the product clearly display a supplement facts panel with ingredients, dosage, and ingredient quantities? Or is that information missing?
- Are the claims about the product detailed or supported by research? Or are they vague?
- Does the company include customer feedback, both positive and negative? Or do they only show you the 5-star reviews?
- What does the return policy look like? Does the company stand behind its product?
Only a few foods naturally have vitamin D. These include fatty fish, mushrooms, beef liver, and eggs.
“Supplements are effective in raising vitamin D levels and can be equally effective compared to dietary sources of vitamin D,” Lin said. “Studies have shown that even in states where individuals have high sun exposure, there is still a high prevalence of people with low vitamin D levels.”