Benefits of 'Sunshine Vitamin' Not So Clear

By Pat Anson, Editor

Maybe Vitamin D isn’t all it’s cracked up to be.

We’ve reported on several studies showing that low levels of Vitamin D are linked to a variety of chronic pain conditions, as well as anecdotal reports that taking Vitamin D supplements can relieve pain and make you feel better.

But a Canadian researcher says there is very little evidence that the “sunshine vitamin” does any of that.

"Wouldn't it be great if there was a single thing that you or I could do to be healthy that was as simple as taking a vitamin, which seems benign, every day? There is an appeal to it. There is a simplicity to it. But for the average person, they don't need it," says Michael Allan, a professor of Family Medicine and director of Evidence Based Medicine at the University of Alberta's Faculty of Medicine & Dentistry.

Allan is the lead author of a review published in the Journal of General Internal Medicine that examines the evidence for 10 common beliefs about vitamin D. Those beliefs include the ability of vitamin D to prevent rheumatoid arthritis, treat multiple sclerosis, reduce falls and fractures, and improve depression.

The review found little evidence that Vitamin D supplements have much effect at all.

"Even areas that we really thought there was good evidence for benefit early on, don't seem to be bearing out," says Allan. "It makes it really difficult to determine a lot of time if there is anything substantial there that you could tell a patient, 'You can take this and it can help you this much.' There's really not nearly enough there to say that."

Allan and his colleagues did find evidence that Vitamin D can have an impact in reducing the number of falls and fractures among the elderly. But the effect is minor.

"Many people would say taking a drug for 10 years to stop one in every 50 fractures is probably not enough to be meaningful. And that's the best vitamin D gets as far as we know now," he said.

There have been over 1,600 studies conducted on Vitamin D in the last decade alone, but Allan says much of the research was poorly executed and is of low quality. He doesn’t dispute the overall health benefits of Vitamin D – such as building strong bones and teeth -- but thinks taking supplements is unnecessary and could even be harmful in large doses.

Most people get all the Vitamin D they need by being exposed to ultraviolet rays in sunlight. You can also get it by eating foods rich in Vitamin D, such as oily fish and eggs.

“Evidence does not support vitamin D supplementation for the treatment of multiple sclerosis and rheumatoid arthritis or for improving depression/mental well-being. Regular testing of 25-hydroxyvitamin D is generally not required, and mega-doses appear to increase harms,” Allan said. “Much of the evidence is at high risk of bias, with multiple flaws, including analyses of secondary endpoints, small and underpowered studies, inconsistent results and numerous other issues. Therefore, enthusiasm for a vitamin D panacea should be tempered.”

Despite the lack of evidence, belief in the benefits of vitamin D supplements remains strong. Allan believes much of it stems from misplaced trust in studies that show low vitamin D blood levels are linked with poor health. However, association does not prove causation.

"The 40 year old person is highly unlikely to benefit from vitamin D," says Allan. "And when I say highly unlikely, I mean it's not measurable in present science."