Many people swear by the benefits of vitamin D supplements, including that it can treat multiple sclerosis (MS) or depression. However, a new study is throwing water on those supposed benefits, arguing that scientific evidence simply doesn’t back them up.
Michael Allan, MD, a professor of family medicine and director of evidence-based medicine at University of Alberta’s Faculty of Medicine & Dentistry, examined evidence regarding 10 common beliefs about the benefits of vitamin D. Among them: Improving depression and mental well-being, preventing rheumatoid arthritis, treating MS and cutting cancer risk.
However, as he reported in the Journal of General Internal Medicine, vitamin D supplementation doesn’t have much of an impact at all.
“Even areas that we really thought there was good evidence for benefit early on, don’t seem to be bearing out,” Allan said in a statement. “The one that we probably have the most evidence for is fractures. If you were to take a group of people who were at higher risk of breaking a bone — so had about a 15% chance of breaking a bone over the next 10 years — and treated all of them with a reasonable dose of vitamin D for a decade, you’d prevent a fracture in around one in 50 of them over that time.”
Allan notes that most people would agree that taking a drug for a decade or more that would only impact 1 in 50 fractures is “probably not meaningful.”
Even though there is a lack of concrete evidence on the benefits of vitamin D, millions of Americans turn to the vitamin daily. Allan argues that the reason for the high utilization is because of prior research that claimed that low vitamin D levels were associated with poorer health outcomes, even though that doesn’t prove causation.
It is also important to keep in mind that taking high levels of vitamin D can potentially be harmful. There are relatively few studies of the effect of taking more than 2,000 IU daily of vitamin D.
In addition, other drugs can influence the absorption of vitamin D. For example, steroid drugs like prednisone, weight loss drugs like Alli (orlistat) and the cholesterol-lowering drug Questran (cholestyramine) can reduce the absorption of vitamin D.