Osteoporosis is one of the most dreaded diseases of aging, often leading to hip fractures and other painful bone breaks that contribute to premature death.
But it is possible to prevent the debilitating disease -- which afflicts an estimated two million Canadians -- by dramatically upping vitamin D consumption, says the scientific advisory committee for Osteoporosis Canada.
The committee says most Canadians need to be popping more of the sunshine vitamin, but particularly those older than 50, who are most at risk of osteoporosis and should take at least 800 International units to 2,000 IU daily, or even more. Those younger need less, but still should be taking 400 to 1,000 IU.
Previously, the group said those under 50 needed only 400 IU and those over 50 needed only 800 IU.
Vitamin makers aren't legally allowed to sell supplements containing more than 1,000 IU vitamin D per dose over-the-counter, so the high end of the range means several pills a day.
The dose guideline is one of the most aggressive by a major public health advocacy group -- depending on the age it is up to five times more than Health Canada currently advises -- and is another sign of the increasing acceptance within parts of the medical community for a larger role for the nutrient.
"Our recommendations are based on our review of the evidence and we can't speak to the factors that Health Canada considered," said Dr. Bill Leslie, head of the advisory committee and professor in the faculty of medicine at the University of Manitoba.
Health Canada and the U.S. Department of Health have an expert panel reviewing current intake guidelines, which were developed based the state of knowledge about vitamin D in 1997, but it is not expected to announce any findings until the fall.
Health Canada recommends 200 IU to 600 IU a day, depending on age and called the group's guideline "premature." It believes "a comprehensive review that looks at both benefits and safety needs to be undertaken before the Department can issue a revised recommendation."
The 2,000 IU figure is the amount Health Canada says is safe to take each day without medical supervision.
The recommendation from Osteoporosis Canada is the third major public health group to say Canadians need to be more mindful of their vitamin D intake, joining the Canadian Cancer Society and Canadian Pediatric Society.
Osteoporosis Canada's revised vitamin D guidelines are being published as a review article in the current edition of the Canadian Medical Association Journal.
Osteoporosis is a disease where the bones gradually lose their calcium, becoming so thin and porous they're more vulnerable to breaking. Vitamin D counteracts the condition because it improves bone mineralization, calcium absorption, and muscle strength, reducing the number of falls people have.
The interest having people up their vitamin D consumption reflects a flurry of research suggesting the nutrient -- up to now linked mainly to curing the childhood bone disease rickets, plays a far wider health role.
Besides preventing osteoporosis, it may also cut the risk of a host of other common chronic ailments, including breast, colon and other cancers, heart disease and multiple sclerosis, although the Osteoporosis Canada science group said these claims need more research.
Scientists say vitamin D could play a role in such a diverse number of conditions because nearly all human cells have receptors for the nutrient, which is converted in the body into a steroid hormone. Hormones are powerful chemicals that control dozens of biological functions.
Researchers say most Canadians don't have enough of the nutrient because it isn't possible to make the nutrient the natural way, through a chemical reaction involving cholesterol in bare skin exposed to strong summertime ultraviolet sunlight, for about half the year during fall and winter. The light connection gives the vitamin D its the sunshine moniker.
"Many Canadians, if not most, are at risk of suboptimal vitamin D status," says Dr. Leslie. "Supplementation is a reasonable preventative strategy."
Researchers looking at the incidence of osteoporosis around the world have a tantalizing clue that it's partly connect to vitamin D insufficiency because the further away from the sunny equator, the more likely people are to have the disease. The osteoporosis rate increases by 0.6 per cent for every 10 degrees of latitude from the equator.
The review said Canadians should have no safety worries about taking up to 2,000 IU a day without medical supervision and even more under a doctor's care because "there is no convincing evidence of adverse effects" of daily intakes up to 5,000 IU a day.
The group the best improvement in clinical outcomes for osteoporosis were attained when people have blood levels of the nutrient above 75 nanomoles/Litre.
With a daily dose of 2,000 IU, most people will match or exceed that target blood level.
The 2,000 IU amount "is a healthy number. It's kind of a compromise. It will probably do the trick for most of the year for three-quarters of the population," says Reinhold Vieth, a professor in the Department of Nutritional Sciences at the University of Toronto.