The best sources of vitamin D

We all know our bodies need vitamin D to stay healthy—but how much should we be getting, and where should it come from? Find out about the best sources of vitamin D, and whether it's better to take supplements or catch some rays

By Lesley Young

The best sources of vitamin D

Vitamin D: It's what you need

We’ve all read the news: Studies suggest that a lack of this “sunshine vitamin” may contribute to higher risks for a host of diseases. Colorectal, breast and prostate cancers, autoimmune diseases such as multiple sclerosis, and even high blood pressure and cardiovascular diseases are associated with vitamin D deficiencies, says Reinhold Vieth, a leading expert on vitamin D and a professor of nutritional sciences at the University of Toronto.

In addition, a groundbreaking Norwegian study published in Cancer Causes and Controls linked higher levels of vitamin D to lower death rates from breast, colon and prostate cancer. And a 2007 study in the Archives of Internal Medicine found that high levels of vitamin D are associated with an overall decrease in total mortality rate.

The best sources of vitamin D

The sun is our most powerful source of vitamin D, which is produced in the skin in response to UVB rays. About 20 minutes of unprotected exposure in the summer, with a UV Index of 7 or higher, will produce 10,000 international units (IU) in a fair-skinned person, says Vieth. But studies have not yet determined what amount of sunlight is needed to produce an adequate amount of vitamin D for disease prevention. And this amount will likely vary for each individual, points out Heather Chappell, senior manager, cancer control policy at the Canadian Cancer Society. “Darker skin is less able to produce vitamin D than fairer skin. Age slows down production, too.”

These research results don’t mean we should all start worshipping the sun, given the risks that come with sunburn and the question marks around the science.

“There’s absolutely no evidence the vitamin D you get from sunshine differs from the vitamin D you get from a supplement,” explains Vieth. The Canadian Dermatology Association recommends adults take 1,000 IU daily as a supplement and forgo sun protection for only a couple of minutes a day.

Health Canada still stands by its current supplement recommendation of 200 IU for adults under age 50 and 400 IU for those over 50, although a review is underway.

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