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Confusing, with a capital D

American report calls into question disease-fighting effect of 'sunshine vitamin'

Hey there, time traveller!
This article was published 5/12/2010 (3614 days ago), so information in it may no longer be current.


American report calls into question disease-fighting effect of ‘sunshine vitamin’


American report calls into question disease-fighting effect of ‘sunshine vitamin’

VITAMIN D advocates are "flipping" over a controversial report released by the Washington- based Institute of Medicine (IOM) this week.

The document backs the well-established idea that vitamin D strengthens bones and fends off osteoporosis. But it states that there isn't enough evidence that the so-called sunshine vitamin has any effect on Type 1 diabetes, cardiovascular disease, multiple sclerosis or cancer.

The news is sure to confuse Canadians. Over the past several years, the public has come to regard vitamin D as a way to ward off such diseases, thanks to studies published in reputable science journals and the subsequent news reports. Those headlines have led to a surge in vitamin D supplement sales as well as an increase in patients asking their doctors to test their blood levels for the vitamin.

Meanwhile, the IOM panel -- made up of 14 vitamin D experts from the United States and Canada -- has significantly increased their vitamin D recommendations for healthy adults under age 71 from 200 IU to 600 IU. As well, the report says that adults over 70 "may" need as much as 800 IU of the vitamin.

The IOM has also increased the tolerable upper intake -- the maximum amount of vitamin D a person can take safely -- from 2,000 IU to 4,000 IU.

"They've told you that as a person younger than 70 years of age that you now need three times as much vitamin D as you did a couple of days ago. They've raised it threefold. And they've told you vitamin D is twice as safe as it ever was," says Prof. Reinhold Vieth, a University of Toronto scientist who spoke with the Free Press recently.

The human body makes vitamin D, also known as the sunshine vitamin, when exposed to sunlight. Many experts say people who live in northern regions such as Manitoba do not get enough sun exposure in the winter months to make adequate amounts of the vitamin. Few foods contain vitamin D aside from dairy products fortified with the vitamin.

Vieth, an outspoken vitamin D advocate who has researched the compound since 1974, has for years urged policy-makers to increase its vitamin D recommendations. He says the IOM has made progress in upping vitamin D recommendations, but is doing Canadians a disservice by not acknowledging that the vitamin does more than strengthen bones. He is certain that the vitamin can ward off several diseases and increase life expectancy. He admits that he and some of his colleagues are frustrated by the IOM's caution.

"I get a ton of email from the vitamin D community where people are flipping. But it's no surprise. I've kind of thrown in the towel years ago. I'm watching it more bemused than anything else," says Vieth.

The IOM came to their conclusions about Vitamin D after examining nearly 1,000 published studies.

The problem, according to Vieth, is the fact that the IOM paid the most attention to randomized, placebo-controlled trials and ignored epidemiological evidence showing relationships between vitamin D intake and a decreased instance of certain diseases.

"Much of what we do in life is not placebo-controlled trials. It's just plain knowledge. You do it and it works," says Vieth.

He also says that the panel was conservative in what they decided would be the tolerable upper intake of vitamin D.

"Ten-thousand units is (what) you'd be making in your bathing suit in the summertime if you went out in your backyard," says Vieth. "For somebody to say you should be afraid of anything other than 4,000 units is absurd."

In the past, scientists urged the public that vitamin E and vitamin A (beta-carotene) were healthy in larger amounts. They've since discovered otherwise.

"They have this background concern that this might be another beta carotene and vitamin E that didn't pan out," says Vieth. "They don't want to tell you to do something and sit back and watch it all melt away. So they'd rather do nothing."

Prof. Glenville Jones, the head of Queen's University biochemistry department and a member of the IOM panel that created the vitamin D report, says the studies Vieth and his colleagues favour are not conclusive.

"There are a lot of what we call observational studies which give us hope that these things are connected to vitamin D, but the problem is it's not clear cut enough that we want to base public health recommendations on that," says Jones.

The professor, who works closely with physicians whose patients have trouble metabolizing vitamin D, admits that the IOM panel was "conservative" in their vitamin D recommendations because they don't want to make decisions based "on hunches or people's best guesses. We want them to be based on facts."

Both Jones and Vieth say that a lack of vitamin D can increase mortality risk. Neither would say how much vitamin D each takes daily. Jones says most Canadians are not deficient in vitamin D. The average person's blood contains about 65 nanomoles/Litre of vitamin D. He says healthy Canadians do not need to get blood tests to check their vitamin D levels.

Vieth, on the other hand, says a healthy person should have blood level of at least 75 nanomoles/Litre of vitamin D and that anything less is "as bad for you as smoking."

Eight years ago, Chris Salstrom, 43, was once so physically weak she wore a leg brace and relied on a crutch to get around.

Doctors were baffled by the Winnipegger's mysterious multiple sclerosis-like symptoms, which included muscle spasms, exhaustion and pain so severe she would sometimes spontaneously fall down.

When her Winnipeg doctors couldn't figure out what was wrong, she went to the Mayo Clinic. One blood test later and doctors there discovered she had a vitamin D deficiency that caused rickets. They ordered her to take 1,000 IU of vitamin D daily. Within a month, her pain and weakness disappeared.

"I'm pretty dedicated to taking it. I don't think there's ever a time that I will stop taking it," says Salstrom, an accountant who now lives in Edmonton. "I know that when I started taking it, the difference in how I felt was so drastic that I never want to stop taking it and risk feeling that bad again."

She says the IOM's new vitamin D recommendations "probably should have come years sooner."

Jones recognizes that people with underlying medical conditions may need to get more vitamin D than his panel suggests. He says not everyone may need to take a vitamin D supplement. But if they do, they should be careful, especially at levels above 4,000 IU.

"Even though toxicity systems arise at much higher levels than that, we don't know what medium level intakes over very long periods of time, like years, will do to you."

Have an interesting story idea you'd like Shamona to write about? Contact her at shamona.harnett@freepress.mb.ca


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