Is Vitamin D a cure-all?

By his own account, Montreal molecular biologist John White is on the conservative side when it comes to vitamin D. But the buzz generated over new vitamin D guidelines issued by the Institute of Medicine, the health arm of the U.S. National Academy of Sciences, makes White look nearly evangelical. The IOM report dared to suggest that North Americans are not lacking in vitamin D. White, of course, flatly disagrees.

In 2001, the McGill University Health Centre professor showed that vitamin D curbs malignant cells, including those involved in breast and prostate cancers. Then White discovered that the vitamin can switch on the body’s own antibodies.

The nutrient has since been hyped as a cure-all. Scientists in the vitamin D field are popping mega-doses, some up to 10,000 international units a day. White supplements with 4,000 IU a day, but only during the six months between fall and spring.

Apart from the hype, however, vitamin D deficiencies have been linked with everything from immune disorders to osteoporosis and childhood diabetes.

Last month, White led a team of scientists from McGill University and the Universite de Montreal in a published discovery that vitamin D deficiency contributes to Crohn’s disease, a painful inflammatory bowel condition. Siblings of Crohn’s patients who have not developed the illness should make sure they’re not vitamin D deficient, one of White’s study collaborators advised.

Last week, seven health-care organizations in Britain announced in a joint statement that Britons should take to the sun for a few minutes every day -and without sunscreen -because of fears of vitamin D deficits. Is the sunshine vitamin back in vogue? Before the era of antibiotics, it was the only effective therapy for tuberculosis.

The Gazette spoke with White in his laboratory about some of the confusion surrounding vitamin D.

White says he is disappointed that the U.S. institute did not take into account vitamin D’s multiple roles and effects in the body beyond bone health. Its recommendations are enough to prevent some deficiencies, he added, but do not go far enough to create optimal health.

The new vitamin D recommendations from IOM: Are they enough?

I was surprised when I realized that they were considering how vitamin D was functioning for its role in bone health and only bone health. I knew that they would be relatively conservative. There’s a perception in the field that a certain level of vitamin D is necessary to maintain skeletal integrity. Whereas there are a number of studies that suggest a level above would be necessary for optimal effect.

Are you speaking about the association of the nutrient with other health issues?

That’s what I’m talking about: diabetes, cardiovascular, infectious diseases, cancer, etc.

Has there been a cause-and-effect established between vitamin D and its protective action?

So this is exactly what the Institute of Medicine is arguing -that really the only case where a cause-and-effect has been established is in the requirementof vitaminDfor maintenance of bones. And that the clinical data out there, while certainly interesting and meriting further study, is not of sufficient rigour for them to take it into account when setting up guidelines on recommended daily allowance.

You obviously don’t agree with that?

Vitamin D is complex. If vitamin D were implicated only in cells that are implicated in skeletal health, in bones, or in intestines that control calcium uptake, well, that would be the end of the story. But the vitamin D receptor is produced in virtually every cell in the body. It’s in the heart, in the immune system, etc. Just based on that alone, it would suggest that most cells in the body would be responsive to vitamin D.

What kind of evidence suggests that vitamin D is doing other things?

There’s a type of cell in the immune system called the macrophage. It’s a professional bug-eating cell, and if a cell dies, these come and mop up the debris. They act like receptors for hormones. But they don’t detect hormones; they detect molecular motifs that are characteristic of pathogens -infectious agents, particularly bacteria. One of the things we’re studying in the lab is what happens when the macrophage responds to vitaminD. Oneof the things it does is ramp up production of the enzyme that takes circulating vitamin D and converts it to its active form (1,25-dihydroxy vitamin D). So now all of a sudden the macrophage in response to an i nfection becomes responsive to the active form of vitamin D. In other words, the macrophage is wired to become vitamin-D responsive. Studies suggest that if someone is deficient that the magnitude of the downstream response is markedly attenuated. We have clear molecular evidence that we are biologically wired to use vitamin D in physiological responses that have nothing to do with bone health. That’s my perspective as the molecular guy.

Are Health Canada and the IOM being overly cautious?

One of the recommendations in the IOM report for total dietary intake from all sources is 600 IU units, enough to achieve a circulating level of 50 nanomoles, (a unit of measure written as nmol/L) which is sufficient for 97.5 per cent of the population. I was really surprised that they came up with that recommendation. I’m no bone expert, but I know enough about it to know that there is evidence in the literature that 50 nmol/L is not sufficient for optimal skeletal health. Nor does it provide optimal protection for the elderly against falls. One of the things that they seemed to take out of the literature was in some studies (a small subset showed some cancer cases went up). Some people in the vitamin D field have gotten religion about this stuff -and dismiss it. I see it and I think red flag. But you have to look at the weight of the evidence.

How much vitamin D do I need to take?

I can’t give you a straight answer to that. That depends on who you are. Vitamin D is a fat-soluble vitamin so if you are obese -guess where it goes? Also, the calcium needs of a growing skeleton are higher than that of a skeleton that’s already grown and is in maintenance phase.

Why are people in the field popping high doses like it’s a religion?

Well that’s a question I ask myself. And I suppose on the surface I am doing exactly the same thing. I put myself at the conservative end of the liberal camp rather than a real liberal. I don’t take any vitamin D in the summer. I take 4,000 units a day for six months of the year in Montreal because that’s the period of the year where I know I won’t get any from the sun. I want to be as transparent as possible. I think the evidence in the literature for a protectiveeffectof vitaminDagainst colon cancer, which is quite a common cancer, is strong. There’s colon cancer in my family, so I said to myself five years ago, do I believe this or not, and if so what am I going to do about it? And I came to the conclusion that based on the weight of the evidence in the literature, there’s a good chance that I was doing myself a benefit and very little chance I was doing myself harm. That was a personal decision. I certainly wasn’t going to wait around for the Institute of Medicine to tell me what to do.