Fighting a Cold? Take D!

(Originally published in the Powell River Peak)

How do you get your vitamins?

Vitamin C comes from oranges, vitamin A from carrots, but the main source of vitamin D is the sun. Vitamin D is the only major nutrient humans can produce themselves.

The good news most people make all they need in 15 to 20 minutes of overhead summer sunlight (longer for those with dark skin).

But that's in summer. According to Dania Matiation, the community nutritionist at Vancouver Community Health, "the bad news is that this far north, in winter, you're probably not getting enough sunlight even if you spend an hour or more outdoors. Which means you need to be looking at your diet, or at supplements."

In northern latitudes, the low level of the sun in the sky means that the ultraviolet B rays that form vitamin D are blocked by the thickness of the atmosphere, even at midday. That's why Scandinavians have used cod liver oil for years, and why the Inuit eat a diet heavy with D-rich animal fats. It's also why Health Canada estimates that the majority of Canadians have a vitamin D deficiency.

It's been known since the 1930s that lack of vitamin D caused a condition called rickets, but it's only in the past few years that a raft of new research has built a strong case that vitamin D, which is technically a steroid hormone precursor, rather than a true vitamin, is critical to everything from immune system function, including fighting cancer, to nervous system development in infants. One study even showed that people with higher levels of the vitamin lived two to three years longer than those with low levels.

Studies are also improving knowledge of how much is needed. The current Health Canada standard of 400 IU (international units) was based on the amount needed to prevent rickets. The new studies indicate that much more may be needed for optimum health, as much as 1,000 to 2,000 IU.

"I think there will be new recommendations from Health Canada in the next few months," said Matiation.

Getting that much isn't practical through diet. Milk is fortified, but only 100 IU per cup. That leaves two options--supplements and tanning booths.

"The booths provide both kinds of ultraviolet, A and B," said Rhonda Boyles, owner of Pacific Breeze Tanning Studios. "It's possible to have a sensible regime of tanning that meets your vitamin needs and doesn't damage your skin." Boyles also works as a receptionist at the Powell River Recreation Complex, another location for tanning. "When you start acquiring the tan," she added, "that's the signal that you're getting enough vitamin D."

One contributing factor to the deficiency problem is that dermatologists, justifiably worried about increasing skin cancer rates, have been discouraging any sun exposure at all, and encouraging use of sunscreen when people do go out. But sunscreen blocks ultraviolet B.

Dr. James Spencer, clinical professor of dermatology at Mount Sinai School of Medicine, New York City, says people can get enough vitamin D from diet and supplements. He recommends fortified milk or orange juice, and eating salmon and other fatty fish, plus taking a 600 IU supplement. "It's so easy," he said. "And it's a lot safer than lying in the sun or climbing undressed into a tanning booth and frying your whole body."

Heather Chappell, senior manager of cancer control policy at the Canadian Cancer Society, agreed that the most reliable source is probably supplements. "The Society recommends that adults start talking 1,000 IU of vitamin D daily in winter, and people with dark skin should take them year round."

Matiation added that, while it's important to consume D, it should be done sensibly. "Don't panic and overdo it," she said, "because too much vitamin D also has toxicity problems." This is especially true for pregnant women, who should consult a physician before adding supplements of any kind.

"A reasonable balance of sun, diet and supplements should work for most people," she said.

Vitamin D Effects
* Promotes immune system function. Why do people get colds and influenza in winter? New studies show it may be low levels of vitamin D.
* Promotes immune system cancer fighting, particularly against colon, breast and prostate cancers.
* Regulates bone density and calcium absorption.
* Low levels may be linked to diseases ranging from high blood pressure to periodontal disease, multiple sclerosis and depression.
* Low levels are strongly linked to muscle aches and bone pain.
* Taking supplements may add as many as one to two years to the average lifespan

Vitamin D Sources
* Fish liver oils, such as cod liver oil, 15 millilitres provides 1,360 IU.
* Catfish, 85 milligrams provides 425 IU.
* Salmon, wild-caught, cooked, 100 milligrams provides 360 IU.
* Mackerel, cooked, 100 milligrams provides 345 IU.
* Sardines, canned in oil, drained, 50 milligrams provides 250 IU.
* Tuna, canned in oil, 85 milligrams provides 200 IU.
* Sun-dried shiitake mushrooms, 13 caps provide 400 IU.
* Fortified cow's milk, 250 millilitres provides 100 IU.