While vitamin D may have other benefits, preventing type 2 diabetes in high-risk adults does not appear to be one of them.

A new Japanese trial found no significant difference among study participants who used a vitamin supplement and those who took a placebo.

“Although treatment with eldecalcitol [an active form of vitamin D used to treat osteoporosis in Japan] did not significantly reduce the incidence of diabetes among people with prediabetes, the results suggested the potential for a beneficial effect of eldecalcitol on people with insufficient insulin secretion,” the researchers said.

For the study, Tetsuya Kawahara from the University of Occupational and Environmental Health in Kitakyushu, Japan, and colleagues assessed whether eldecalcitol could reduce type 2 diabetes risk in 630 individuals with impaired glucose tolerance. They were compared to 626 participants who received a placebo.

The individuals were recruited from three hospitals in Japan between 2013 and 2019. With an average age of 61, about 46% were women and 59% had a family history of type 2 diabetes. They were tested for diabetes every three months over three years.

The upshot: Researchers found no meaningful differences between the groups.

About 12.5% of the eldecalcitol group developed diabetes compared to 14% of the placebo group. Blood sugar levels returned to normal in about 23% of the eldecalcitol group and 20% of the others, the findings showed.

The report was published online May 25 in the BMJ.

After adjusting for other influential factors, the investigators did find that eldecalcitol may prevent type 2 diabetes in some prediabetic patients. The finding is unclear and more research is needed, the study authors noted in a journal news release.

The study also found a significant increase in both lower back and hip bone mineral densities in individuals who took vitamin D.

Not clear is whether the dose the team chose was the appropriate one for preventing diabetes or whether the results could be applied to all ethnic groups.

About 480 million people worldwide have type 2 diabetes, and the number is expected to reach 700 million by 2045. About a half-billion people have impaired glucose tolerance or prediabetes.

While weight loss and exercise can reduce type 2 diabetes risk, they are hard to sustain, prompting a search for new strategies.

In an accompanying journal editorial, Dr. Tatiana Christides of Queen Mary University of London noted that several questions remain. They include whether vitamin D supplementation may be more effective for particular populations, and whether longer treatment or starting at a younger age might be beneficial.

Health care professionals “should continue to discuss with patients the musculoskeletal health benefits of vitamin D and support them to achieve and maintain lifestyle changes that, although challenging to sustain, are known to decrease development of type 2 diabetes,” Christides said.

More information

The American Diabetes Association has more on prediabetes and types of diabetes.

SOURCE: BMJ, news release, May 25, 2022

Source: HealthDay