As we head out of this annoyingly snowbound March, it's practically certain our winter-worn bodies aren't toting enough vitamin D. We northern folks get a lot less of the sun's ultraviolet tonic than everyone else on the planet - and there's sound research showing that we pay a price for it.
I'm not just talking about how imperative the mighty D is for the absorption of calcium. I'm referring to the role it plays in preventing certain cancers like breast and prostate as well as in warding off autoimmune disorders like multiple sclerosis.
Some educated types say we just aren't supplementing enough. Health Canada recommends a minimum daily dose of 200 IU and a maximum of 1,000 IU. Pish-posh! say D advocates. If you're in the lower range of IU intake, call yourself deficient. And some people aren't even getting that.
And don't think you can eat your way into D sufficiency. Sources of this nutrient are limited almost exclusively to animal products like kidney, liver and some fish, though cow's milk and margarine are now D-fortified, as is soy milk as of late. Then, of course, there's the big fiery drugstore in the sky. It won't help you much in the winter, because even on a bright day the sun is still too low.
But the best news is that your body stores D over time. Many advise white folk to soak it up for five to 10 minutes twice a week, with exposure only to the hands, arms and face, while people of colour require up to six times more sunshine. Exposure has to be unprotected, since sunscreen prevents absorption. Health Canada now says that infants exclusively breast-fed should have a supplement of 400 IU per day.
So take advantage of Apollo's chariot over the coming months as it rises heavenward. In moderation, of course. Would we have it any other way?
What the experts say
"If you measured the blood levels of 100 Canadians, easily 80 or 90 would be deficient. In Scandinavia, infants who got higher doses of supplementation were about one-sixth as likely to need a prescription for insulin by the time they were 30.
People become progressively more at risk for multiple sclerosis the further they live from the equator. Those who had one or more sunburns as children were much less likely to end up with MS. In other studies, ultraviolet light exposure is associated with substantial reduction of risk for cancers including breast, prostate and bowel. The only supplement worth taking for an adult would be 1,000 units per day."
REINHOLD VEITH, associate professor of nutritional sciences and pathobiology and laboratory medicine, University of Toronto, vitamin D researcher, Mt. Sinai Hospital, Toronto
"There is really no evidence suggesting that sensible sun exposure will increase your risk of cancer. But there is evidence that sun exposure decreases the risk of melanoma and of dying of melanoma. We have data that shows SPF 8 sunscreen reduces your ability to make vitamin D by 95 per cent. Those who say supplements of 1,000 IU or more can cause toxicity are totally mistaken. Upwards of 5,000 to 10,000 units daily can put you at risk of toxicity. We had a case where a man was taking what he thought was 1,000 units in a teaspoon twice a day, but the company forgot to dilute it, so he was taking over 1,000,000 units a day. That can cause toxicity. You can wind up calcifying your kidneys and having kidney failure and heart failure or death if undetected. Back in the early 90s, we measured vitamin D content in milk throughout the U.S. and western Canada. No more than half of the samples contained 50 per cent of what was stated on the label. Most chronic diseases can be prevented by increasing your intake."
Michael Holick, MD, director of the vitamin D research lab, Boston University Medical Center, author of The UV Advantage
"Animal studies show that vitamin D can prevent autoimmune diseases. The ones we know the most about are rheumatoid arthritis, lupus, multiple sclerosis and type one diabetes. There have been studies of MS showing that supplements can reduce the incidence of MS, but those supplements are now considered totally inadequate, meaning that a higher dosage might have suppressed it altogether. Dermatologists should not be telling people to stay out of the sun without telling them they must take vitamin D supplements. I get my clients to get their doctors to measure their blood levels for vitamin D once a year, and I want those levels to be not in the "normal" range in Toronto but in the normal range for a Louisiana lifeguard. Everyone needs to take a minimum of 1,000 units. Some people need lots more."
Aileen Burford Mason, immunologist/dietitian "The best source of vitamin D is canned fish . Some is added to margarine . Also fluid milk and fortified soy beverage. There's a tiny bit in egg yolk , and that's pretty much it. The best way to get it, although sometimes people have a problem publishing this because of sun safety, is through brief sun exposure from mid-April to mid-October. Most people can get that running to the subway. Deficiency is actually a problem for a lot of people just because they aren't consistent milk drinkers and not everybody eats canned fish."
DOUG COOK, registered dietitian, Toronto
"Most Canadians spend more than two hours a day in the sunlight, and half the population get one or more sunburns during the course of the summer. The amount of sunlight you need for vitamin D metabolism is five to 10 minutes twice a week, with exposure only to the hands, arms and face. Tanning bed operators say their method prevents every form of illness because it gives you vitamin D. That hasn't yet been documented and is not based on known facts. Most people who are suffering from a deficiency are those from the Middle East who wear dark clothing or burqas all the time."
JASON RIVERS, MD, professor of dermatology, University of British Columbia, Vancouver