The new Canada Food Guide, released to the public February 2007, made food guide history when it recommended that Canadians over the age of 55 take a 400 IU vitamin D supplement. Proponents of the vitamin – and they are many – applaud the move, but say it doesn't go far enough.
Dr. Reinhold Vieth, director of the Bone and Mineral Laboratory, Department of Pathology and Laboratory Medicine at Mount Sinai Hospital in Toronto, contends that Canada's northern latitude means we get fewer of the vitamin D-forming rays of sunlight, which are our primary source of vitamin D. The health benefits of increased levels of vitamin D, says Vieth, are important and largely underreported. “The story for vitamin D doing good is at least as powerful in terms of the evidence as is the story that smoking is doing bad.”
In fact, Osteoporosis Canada encourages adults over 50 to take double the amount recommended in the new Canada's Food Guide – 800 IU.
What does Vitamin D do?
Vitamin D is an important factor in calcium absorption, increasing it by 30 to 80 percent, so we know that vitamin D is critical to good bone health, but many people aren't aware of the link between low levels of vitamin D and other health issues.
Vitamin D and Cancer
In May 2006, the first North American conference on UV, Vitamin D and Health released key findings about the health effects of vitamin D, including a statement acknowledging “ a growing body of evidence that vitamin D may have beneficial effects on some types of cancer, in particular colorectal cancer.”
Vitamin D and Schizophrenia
There has also been research suggesting elevated intake of Vitamin D (2000 IU) early in life could reduce the risk of schizophrenia in men. The study, from Australia, did not find a similar link in women and Vitamin D intake.
According to Mount Sinai researchers, neurological diseases (schizophrenia, bipolar disorder, autism, Alzheimer's) are more prevalent in people who are born in seasons when Vitamin D concentrations/sunshine is low.
Vitamin D and Diabetes
There's also evidence of a connection between Vitamin D and diabetes. Giving a vitamin D supplement during childhood appears to protect against type-1 diabetes, while low levels of vitamin D have been linked to the risk of developing type-2 diabetes.
Vitamin D and Multiple Sclerosis
“In a controlled study in the 1980s, blood samples of United States military personnel were taken and stored,” says Dr. Vieth. “In the late 1990s a check on those samples revealed that those with low vitamin D when the samples were taken were nearly four times as likely to end up with multiple sclerosis.”
Can't Get Enough?
Milk is an excellent source of vitamin D, with one 250-millilitre glass containing 100 IUs. Other sources supplying smaller amounts of vitamin D include margarine, eggs, fortified orange juice, almonds, beans, broccoli, figs, salmon, herring, swordfish and cod and liver oils. Osteoporosis Canada recommends a vitamin D supplement, noting that it's sometimes difficult to get enough vitamin D from the foods we eat.
Will we be hearing more about vitamin D and its importance to our health? We should be, says Dr. Vieth. “The story on vitamin D is not over, by any means.”