New vitamin D guidelines divide health experts
CTV.ca News Staff
Published Tuesday, November 30, 2010 9:58PM EST
A major new U.S-Canadian report calls for an increase in the daily recommended intake of vitamin D, but not to the levels many health organizations have been urging because of mounting evidence linking the "sunshine vitamin" to the prevention of chronic disease.
After reviewing nearly 1,000 published studies along with testimony from scientists and others, an expert committee from the trusted Institute of Medicine agreed that vitamin D and calcium play a role in maintaining strong bones. But they also said there was not enough strong evidence yet that vitamin D plays a role in preventing chronic illnesses, such as cancer and diabetes.
The IOM's report raises the recommended Dietary Reference Intakes of vitamin D, but says the changes are focused primarily on bone health.
"In respect to some of the other diseases that we looked at, we just didn't have enough evidence yet to definitively say what level of vitamin D or how much supplements to take to prevent heart disease or cancer," Dr. Clifford J. Rosen, a member of the IOM panel, explained to CTV's Canada AM Tuesday morning from Washington.
"We focused on skeletal or bone health because that was the primary outcome in which there were enough studies to conclude what we did."
The IOM raised its daily recommended intake for vitamin D to:
- 600 International Units of vitamin D a day for most people (up from 200 IU)
- 800 IUs per day for people 71 and older (up from 600 IU)
- breastfed babies need 400 IU daily, a level the panel continues to endorse
As for calcium, it recommends:
- 700 milligrams per day of calcium for most toddlers ages 1 through 3
- 1,000 mg daily for most children ages 4 through 8
- 1,300 mg per day for adolescents ages 9 through 18
- 1,000 mg per day for most women ages 19 through 50 and for men until age 70
- 1,200 mg per day for women over 50 and for both men and women over 70
The panel concluded, after reviewing national surveys of blood levels of both vitamin D, "the majority of Americans and Canadians are getting enough" from our diet and the sun and do not need to take supplements.
"We're getting about 200 to 300 units just in our food sources alone," Rosen noted, adding that most of us are getting the rest through supplements and sunshine.
Health Canada has yet to formally approve the recommendations, but their website has already increased its recommended limits.
However, several health organizations have called for high doses of vitamin D in recent years, and some are standing by those recommendations, saying the report only focused on bone health.
In 2007, the Canadian Cancer Society recommended that all adults consider taking 1,000 extra IUs of vitamin D daily throughout the winter because of the lack of sunlight. Those with darker skin and those who get little exposure to sunlight should consider taking 1,000 IU daily year-round.
On Tuesday, the society told CTV News that it will not be changing its recommendations because of "the growing body of evidence about the links between vitamin D and cancer risk."
"The IOM report focused on recommendations for bone health and our mandate is cancer," Cancer Society spokesperson Alexa Giorgi said in an email.
Dr. Reinhold Vieth, a professor in the University of Toronto's Department of Nutritional Sciences says he's disappointed that the IOM panel focused only on bone health.
"I think other conditions besides bone health should have counted, but they ignored them," he told CTV News.
"The amount of vitamin D that helps bone is not entirely appropriate and not enough for other types of conditions," he said. "That is evolving evidence and to ignore that type of evolving evidence is not quite right."
Still, while the new vitamin D recommendation of 600 IU a day is a big jump from the 200 IU previously recommended, the panel cautioned against assuming that if a little vitamin D is good, that more must be better.
It noted that research on the vitamin is just beginning and cautioned that other vitamins once touted as health boosters, such as beta-carotene and vitamin E, later turned out to be dangerous at higher levels.
The IOM panel noted that most of the research so far on vitamin D has only been able to draw links between intake and health effects; they have not conclusively proven that the vitamin is causing the effects.
"While these studies point to possibilities that warrant further investigation, they have yielded conflicting and mixed results and do not offer the evidence needed to confirm that vitamin D has these effects," the IOM said in a news release.
The report also warns against taking high doses of vitamin D, noting that there are still too many unknowns about the risks of doing so.
"Getting too much calcium from dietary supplements has been associated with kidney stones, while excessive vitamin D can damage the kidneys and heart," they wrote.
Because there is some evidence of the risk of death or chronic disease from long-term high vitamin D and calcium intake, the panel also issued "tolerable upper intake levels" (UL) for each supplement – the maximum it recommends per day, raising the limits in all cases:
- 2,500 IUs per day of vitamin D for children ages 1 through 3
- 3,000 IUs daily for children 4 through 8 years old;
- 4,000 IUs daily for all others.
- 2,500 milligrams per day of calcium from age 1 through 8
- 3,000 milligrams daily from age 9 through 18
- 2,500 milligrams daily from age 19 through 50
- 2,000 milligrams daily for all other age group
Dr. Vieth said he's pleased to see the upper limits were raised to 4,000 IU, saying it now allows researchers to study the health effects of higher levels of the vitamin without ethical questions.
Health Canada closely follows The Institute of Medicine's recommendations on Dietary Reference Intakes while setting standards for food labelling, updating the Canada Food Guide, setting nutrition standards for school and nursing homes, and other matters.