Vitamin D supplements are commonly used to protect against bone loss and fractures. However, new research suggests another benefit for people with pre-diabetes: it may help lower their risk of developing full-blown diabetes.
Three clinical trials were conducted to investigate the effect of vitamin D supplements on pre-diabetic patients. The results showed that vitamin D was modestly effective in reducing the risk of pre-diabetes progressing to type 2 diabetes. Over a three-year period, just under 23% of study patients who used vitamin D developed diabetes, compared to 25% of those who were given placebo pills. On average, the study found that supplements reduced the risk of progression to type 2 diabetes by 15%.
Lead researcher, Dr. Anastassios Pittas from Tufts Medical Center in Boston, stated that the findings only apply to people who are at high risk for the disease and it is still unknown what the optimal dose of vitamin D is for people with pre-diabetes. He emphasized that no supplement should replace lifestyle changes such as a healthy diet and regular exercise.
Type 2 diabetes occurs when the body’s cells no longer respond properly to insulin, which helps move sugar from food into cells for energy. This results in high blood sugar levels, which can cause damage to blood vessels over time and lead to complications such as heart, kidney, and eye disease. Pre-diabetes is a state where blood sugar is abnormally high, but not yet high enough to diagnose type 2 diabetes. In the United States, approximately 96 million adults have pre-diabetes.
The study on vitamin D was initiated due to the observation that diabetes is more prevalent in areas farther from the equator. This led to the suggestion that exposure to sunlight, which stimulates the body to produce vitamin D, may play a role in diabetes risk. Further research found a link between blood levels of vitamin D and the risk of type 2 diabetes, and lab research indicated potential reasons for this, such as the ability of vitamin D to restore normal insulin production in animals.
Three clinical trials directly tested the effect of vitamin D supplements on the odds of pre-diabetes progressing to type 2 diabetes. Each trial showed that participants given vitamin D had a lower risk compared to those given a placebo. However, the difference was not statistically significant, meaning the supplement could not be declared effective. To detect a moderate effect of vitamin D, a meta-analysis was conducted to combine the data from all three trials. The analysis, which was published in the Annals of Internal Medicine, included over 4,000 adults with pre-diabetes and found that just under 23% of supplement users developed type 2 diabetes, compared to 25% of placebo users.
The modest difference in the results suggests that vitamin D can delay diabetes in up to 10 million people worldwide with pre-diabetes. It is important to note that overall lifestyle changes are still necessary to halt the progression of pre-diabetes. However, adding a vitamin D supplement can be an easy and low-cost way to get additional protection. People with pre-diabetes should talk to their doctor and get their blood vitamin D levels measured if they have not already. Further research is needed to determine the optimal dose of vitamin D for people with pre-diabetes. It is generally recommended that the daily dose of vitamin D should not exceed 4,000 IU, as high levels of vitamin D stored in body fat can cause problems such as kidney stones. The three trials showed that just over 1% of participants developed kidney stones, and supplement users were not at a greater risk.