Most Canadians and Americans are receiving enough vitamin D and calcium, according to a new report that triples current recommendations for the sunshine vitamin.
The U.S. and Canadian governments asked the Institute of Medicine to assess data on calcium and vitamin D in human health and to update the dietary reference intakes, or DRIs, that appear on nutrition labels for packaged foods.
The report, released Tuesday, concluded that most people in Canada and the U.S. need 600 international units of vitamin D per day, triple Health Canada's current recommendation of 200 IU for adults aged 19 to 50. People 71 and older may require as much as 800 IUs per day because of potential physical and behavioural changes related to aging.
The recommendations are not just for a supplement or diet but for the combination of both sources, said committee chair Catherine Ross, who is also a professor of nutritional science at Penn State University, University Park.
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The recommendations assume minimal exposure to the sun, which naturally boosts vitamin D levels.
There isn't enough evidence that vitamin D helps protect against cancer, heart disease, autoimmune diseases and diabetes, but further investigation is warranted, the group said.
"The committee emphasizes that, with a few exceptions, all North Americans are receiving enough calcium and vitamin D," the report concluded.
"Higher levels have not been shown to confer greater benefits, and, in fact, they have been linked to other health problems, challenging the concept that 'more is better.'"
The panel set an upper limit for vitamin D, concluding that once intake exceeds 4,000 IU per day, the risk for harm starts to increase.
Very high levels of vitamin D, above 10,000 IUs per day, are known to cause kidney and tissue damage, according to the report.
The evidence does strongly support the importance of vitamin D and calcium in promoting bone growth and bone maintenance, the report's authors said.
"This is a stunning disappointment," said Dr. Cedric Garland of the University of California, San Diego, who wasn't part of the institute's study and says the risk of colon cancer in particular could be slashed if people consumed even more vitamin D.
"I believe we should be using significantly more," agreed Dr. Gerry Schwalfenberg, a family physician in Edmonton and an assistant clinical professor in the department of family medicine at the University of Alberta.
"I would be suggesting, at least for our latitude, and our amount of sun that we’re getting, a minimum of 1, 000 [IU] and probably 2,000 [IU] would be where I find most people would get levels that would help to prevent chronic disease," added Schwalfenberg, who has written several papers on vitamin D.
Vitamin D blood test not standardized
Vitamin D blood tests are more widely used now than a few years ago. But the measurements used by labs to report deficiencies have not been based on rigorous scientific studies, and no central authority has standardized measurements, the committee noted in the report.
Someone could be deemed deficient or sufficient depending on which laboratory did the blood test, the authors said.
Health Canada said Tuesday that it welcomed the recommendations.
"While the recommended amounts of vitamin D per day have increased for everyone, this does not mean that Canadians need to change their current food or supplement intakes," Health Canada said in an email. "Based on Health Canada’s preliminary analysis of Canadians vitamin D blood levels, most are currently meeting their needs for vitamin D."
The Canadian Cancer Society recommends Canadians take in 1,000 IU — 25 micrograms — of vitamin D every day.
"Our recommendation is based on the growing body of evidence about the links between vitamin D and cancer risk, and as a result, we will not be changing our recommendation at this time," the society said.
Vitamin D can be obtained from milk, fortified milk alternatives, fish, liver and egg yolk.
As of Dec. 1, Ontario is delisting vitamin D testing for most of the population. Manitoba, Nova Scotia, Newfoundland and Labrador, Prince Edward Island and Saskatchewan have made similar moves.