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WHAT'S NEW
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March health news: Vitamin D battles breast and colorectal cancers
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Two new studies shine a bright light on the sunshine vitamin
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By Heather Camlot
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Good day, sunshine! Two new studies about vitamin D shed a bright light on the sunshine vitamin's positive effect on breast and colorectal cancers.
The findings
"What we found is that 2,000 international units a day of vitamin D3 would produce a serum level of vitamin D that would correspond to getting rid of two-thirds of colorectal cancer," explains Dr. Cedric Garland, the studies' co-author. "We also found that the same [amount] would eliminate about half the breast cancer incidents."
These findings come from meta-analyses -- a high-tech method in which data from multiple reports are combined for a more precise estimate. The studies were conducted by a team of cancer prevention specialists at the Moores Cancer Center at the University of California, San Diego as well as by colleagues on both coasts.
Breast cancer research
For the breast cancer meta-analysis, published online in the Journal of Steroid Biochemistry and Molecular Biology, the data from two previous studies involving 1,760 people were divided into five equal groups, from the lowest blood levels of vitamin D (less than 13 nanograms per millilitre) to the highest (about 52 ng/mL). The data showed conclusively that the higher the amount of vitamin D in the blood, the lower the rate of breast cancer.
Colorectal cancer research
Similarly, the colorectal cancer meta-analysis, published online in the American Journal of Preventive Medicine, pooled data from five studies involving 1,448 people and found that when individuals took 2,000 IU of vitamin D a day (about 46 ng/mL), the rate of colorectal cancer dropped by two-thirds.
Recommended intake of vitamin D
At 11 ng/mL, Canadians as a nation have one of the lowest blood levels of vitamin D in the world, says Garland. And in its revised Food Guide to Healthy Eating, Canada recommends only 400 IU of vitamin D. "We know that 400 is too little," says Garland. "While it's adequate to prevent rickets, and it will help with the reduction of the risk of fractures, it's a fifth of the amount that's needed to have an impact on breast cancer."
Research by Reinhold Vieth, director of the Bone and Mineral Laboratory at Mount Sinai Hospital in Toronto, has shown that daily vitamin D dosages of up to 10,000 IU are safe.
How much to soak up the sun for vitamin D benefits
To get your dose of vitamin D, Garland suggests that Canadians spend 15 to 20 minutes outside every day to take in an adequate amount of vitamin D via the sun.
Those with fairer skin may need less time outside, while those with darker skin will need more to achieve the same effect. "For people who can get in the sun, there really is nothing quite like it. That amount of time in the sun produces 10,000 IU of vitamin D, and we're only recommending 2,000 IU," says Garland.
How to expose your skin for vitamin D benefit
How much you cover up can also affect your sun-induced vitamin D absorption. "Most people...expose only the hands and face, which is only eight per cent of the body surface area, and it takes 40 per cent of the skin to be exposed to make 10,000 units," he says. "It may be better to err on the high side, take the supplement every day of the year at Canada's latitude but then when weather allows, get out in the sun -- but never to a point where it burns."
You'll also want to keep your sunscreen in your back pocket until those 20 minutes elapse since it completely prevents your body from absorbing vitamin D from the sun. Though that advice goes against what the Canadian Cancer Society tells us about applying sunscreen -- at least 20 minutes before heading outdoors -- Garland offers this perspective: "In the United States we have only 2,500 deaths a year from non-melanoma skin cancer. Yet we have more than 250,000 deaths from cancers combined."
In addition to getting vitamin D from the sun, you can get the recommended 2,000 IU of vitamin D in a supplement or from oily fish such as salmon, and in milk. Says Garland: "Taking vitamin D is a cheap, easy way to reduce the rate of cancers."
How much do you know about breast cancer? Take our quiz to find out.
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