PhotoVitamin D is sort of like Mom, apple pie, and so forth. But a new Canadian study finds there's little scientific evidence to back up all the claims made for the popular vitamin.

We get vitamin D from the sun, of course, but many people also pop it in the form of tablets as well, thinking it helps with depression, multiple sclerosis, and other maladies.

But according to Michael Allan, director of Evidence Based Medicine at the University of Alberta's Faculty of Medicine & Dentistry, much of that belief isn't validated by science.

"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 Allan.

Little evidence

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. His team wanted to know if it really can reduce falls and fractures, improve depression and mental well-being, prevent rheumatoid arthritis, treat multiple sclerosis, and lessen incidences of cancer and mortality.

The verdict: there's little evidence that supplementation with the vitamin has much of an effect at all. Vitamin D supplementation does seem to have a "minor impact" in reducing falls among the elderly, but that's about it.

"If you were to take a group of people who were at higher risk of breaking a bone -- so had about a 15 percent 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 said.

Not measurable

"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."

Allan says many of the previous studies that claimed benefits for the supplement simply weren't well done. The bottom line, he says, is that while moderate vitamin D supplementation won't cause harm to the average healthy person, it won't heal either.

"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."

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