Osteoporosis Canada now says adults over 50 can safely take up to 2,000 international units of vitamin D a day to keep their bones strong.
The organization released its updated recommendations on Monday, noting that the former Canadian guidelines on the vitamin were more than 10 years old and did not reflect current research. The new guidelines are published in this week's issue of the Canadian Medical Association Journal.
The new guidelines recommend that adults under age 50, without osteoporosis or conditions affecting vitamin D absorption, should aim to take daily supplements of 400 to 1,000 international units of the vitamin.
"A daily supplement of 25 mg (800 IU) should now be regarded as a minimum dose for adults with osteoporosis," write Dr. David A. Hanley from the University of Calgary Health Sciences Centre, and coauthors.
Those over 50 with or without the bone-thinning condition can safely take between 800 and 2,000 IU. But Hanley's team notes that adults shouldn't go above 2,000 IU a day without the advice of a doctor.
"Canadians can safely take daily vitamin D supplements up to the current definition of tolerable upper intake level (50 micrograms [2000 IU]), but doses above that require medical supervision," they write.
Previously, the group said those under 50 needed only 400 IU and those over 50 needed only 800 IU.
Vitamin D, along with calcium, is essential for preventing and treating osteoporosis, which can lead to fractures. Recent research has suggested the vitamin may also reduce other health risks such as some types of cancer, diabetes and immune system disorders.
The authors note because of Canada's geographical latitude, Canadians are at risk for vitamin D insufficiency.
They note that while most active Canadians get adequate vitamin D levels in the summer through the sun, by winter, vitamin D stores in the blood of many Canadians can fall by half.
"The influence of diet on vitamin D status is minimal… and most circulating vitamin D is derived from exposure to sunlight," the authors write.
They add still more research is needed into optimal doses and safe upper limits for vitamin D intake.
"Despite a great deal of new research in the past decade, these major clinical questions have still not been addressed to the satisfaction of most experts in the vitamin D field," they write.
Three years ago, the Canadian Cancer Society released its own guidelines, based on research suggesting that vitamin D may reduce the risk of some cancers. The society recommended that all adults consider taking 1,000 IUs a day during the fall and winter.
Those with dark skin, who are at higher risk of insufficiency because they don't absorb as much of the vitamin from the sun, should consider taking that amount all year round, the Society recommended.
Health Canada and the U.S. Department of Health have an expert panel reviewing current vitamin D intake guidelines. That update is expected in the fall.
