If you’re taking vitamin D to lower your risk of developing type 2 diabetes when you get older, it’s time to lower your expectations.
A new study, the largest of its kind, has found that taking 4000 international units (IU) per day, which is the safe daily upper limit, increases the amount of vitamin D in the blood, but doing so does not change a person’s risk of developing diabetes compared to people who don’t take the vitamin.
After about 2.5 years, diabetes appeared at a rate of 9.4% per year with vitamin D supplements and 10.7% with placebo capsules, an insignificant difference. All the patients were already at high risk for developing type 2 diabetes and 80% already had adequate levels of the vitamin.
For the 5% of the study population who had very low levels of vitamin D, there appeared to be a benefit, but the researchers urged caution in reacting to that finding as the numbers were too small to prove.
About the study
The study involved 2,423 volunteers who were at high risk for developing type 2 diabetes, which can often be prevented with diet and exercise.
About 29 million Americans already have type 2 diabetes and it is the 7th leading cause of death in the
Previous research has found that people with low levels of vitamin D have an increased risk of developing type 2 diabetes. The new study, known as D2d, was designed to test whether supplementation would cut the odds.
All the volunteers met two out of three criteria for pre-diabetes, making it more likely that vitamin D - if effective - would help them.
Ultimately, 616 developed diabetes: 293 in the vitamin D group and 323 who were taking placebo capsules. The researchers found that the risk of developing type 2 diabetes in each group was too similar to indicate that vitamin D made a big difference.
In contrast, earlier randomized controlled trials have shown that lifestyle changes such as diet and exercise can lower the risk of developing type 2 diabetes by 58% over a similar period of time.
Preventive treatment with the drug metformin can lower it by 31%.
Bottom line: Weight loss and increasing physical activity is still the best way to prevent diabetes.”
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