Health benefits of Vitamin D

Getty Images

The sunshine vitamin has been soaking up the spotlight over the past few years, touted as an immune-boosting cure-all for everything from the flu to cancer. But some experts caution that the hype is overblown and, if anything vitamin D is only one piece in a very complex puzzle.

Here's what we know. Experts agree that vitamin D is important for maintaining healthy bones by helping our bodies absorb calcium, and it plays a key role in supporting our immune systems. "The immune system is like a soldier that protects you," says Reinhold Vieth, a professor of nutritional sciences at the University of Toronto and a clinical biochemist at Toronto's Mount Sanai Hospital. "With more vitamin D, your immune system becomes a smarter soldier that can tell friend from foe."

How? According to Sreeram Ramogopalan, a researcher at Oxford University, vitamin D helps our immune systems target foreign cells (like viruses) while preventing it from targeting our own healthy cells.

       That's why, says Ramagopalan, a growing body of research has started to look at how vitamin D deficiency affects a range of autoimmune diseases such as multiple sclerosis, rheumatoid arthritis and type 1 diabetes. A link might explain why these diseases are more prevalent the farther you get from the equator, because people closer to the poles don't soak up as much sun.

Getting adequate levels of vitamin D might also help us ward off all kinds of infections. A new Japanese study published in the American Journal of Clinical Nutrition found that children who took 1,200 IUs of vitamin D daily all winter were significantly less likely to get the flu than kids who only took a placebo.

Many health officials have backed away from these claims, saying the research is just too preliminary to draw conclusions. Since the craze began, patient testing of vitamin D levels has skyrocketed: up more than 2,000 percent in Ontario since 2004 (costing an estimated $66 million this year). In August, the government of Ontario proposed pulling funds for individual vitamin D tests, joining five other provinces that feel the proof is too weak.

Statistics Canada estimates that three million Canadians aren't getting adequate vitamin D. How much do we need? Vieth recommends following guidelines from the Canadian Cancer Society. Osteoporosis Canada and the Canadian Dermatology Association: Adults should take a 1,000 IU supplement every day during fall and winter. And if you are at risk of deficiency (over 50, dark skinned, don't go outside often, wear clothing that covers most of you), you should take 1,000 IU a day all year round.

Your body needs to be exposed to ultraviolet rays to make vitamin D by itself. Both Vieth and Ramagopalan recommend spending about 10 to 15 minutes outside (without sunscreen, which blocks UV rays from being absorbed) every day in the warm, sunny months. When it's too cold to go for a walk or sit in the park, for your dose from your diet or a daily supplement.