NUTRITION
June 22, 2016

Reconsidering Vitamin D

Studies showing vitamin D improves health may be flawed, but does that mean they're wrong?

Vitamin D is an important nutrient, and it’s a best seller in the vitamin aisle; but its value as a supplement may have been oversold. It's possible that you don’t need to do anything more than go outdoors a little more to get all you need.

In a recently published review, Canadian researchers looked at 10 of the most common beliefs about vitamin D and the scientific evidence to back up those beliefs. The researchers examined claims that the vitamin could reduce falls and fractures; improve mental health, including depression; prevent rheumatoid arthritis; aid in the treatment of Multiple Sclerosis; and reduce the incidence of cancer.

Better quality research needs to be done if vitamin D supplementation is to have any clinical significance.

They found that vitamin D supplementation doesn’t have much effect on any of these things. Some of the benefits that looked good in early research don’t seem to be as strong as once believed. Of all of the supposed benefits of vitamin D, the one that had the strongest evidence was reducing the number of falls and fractures among the elderly, but, even then, the impact was small.

According to a statement by Michael Allan, professor of Family Medicine and director of Evidence Based Medicine at the University of Alberta, “If you were to take a group of people who were at higher risk of breaking a bone — so had about a 15 per cent 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.” And that’s just not enough of a benefit to be meaningful, according to Allan.

The problem is that much of the research into vitamin D simply suggested low vitamin D levels were associated with poor health outcomes. The studies did not prove that low levels of the vitamin caused health problems, only that when a person was low in vitamin D, the risk for certain health issues was also higher.

Better quality research needs to be done if vitamin D supplementation is to have any clinical significance.

Taking moderate amounts of vitamin D isn’t harmful to a healthy person, but it isn’t particularly helpful either. The Dietary Reference Intake for adults is 600 international units (IU) or 15 micrograms (mcg) per day. After the age of 70 it increases to 800 IU or 20 mcg. The Tolerable Upper Intake level (UL) is 4,000 IU or 100 mcg, and long-term intakes at that level or above increase the risk for health problems.

Often called the sunshine vitamin because of the body’s ability to make the vitamin when exposed to the ultra-violet rays of the sun, vitamin D is a rarity in food. About the only good food sources are fatty fish (tuna, mackerel, salmon) and fish liver oils with small amounts found in beef liver, egg yolks, cheese, and fortified foods like milk, margarine and yogurt.

“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,” Allan said.

Maybe the best advice concerning vitamin D supplements is to save your money and go outside and play.

The review is published in the Journal of General Internal Medicine.

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