Popping a vitamin D pill every day may give people a significant edge in reducing their odds of having heart disease, the leading cause of premature death in Canada.
Doctors at the Intermountain Medical Center Heart Institute in Murray, Utah, reviewed 31,000 of their patients and found that those with the lowest levels of vitamin D in their blood had a 170-per-cent greater risk of heart attacks than those with the highest amounts of the nutrient.
The patients, all aged 50 or older, were placed into groups based on how much vitamin D they had and then tracked for more than a year to see what kind of medical problems they experienced.
"We think that this study … certainly adds further evidence to suggest that if you have low vitamin D and you treat yourself, you may have less heart disease," said Brent Muhlestein, director of cardiovascular research at the institute.
The benefits of having more vitamin D were not limited to a cut in heart-attack risk.
Those with the lowest readings also had an 80-per-cent greater risk of death, a 54-per-cent higher risk of diabetes, a 40-per-cent higher risk of coronary artery disease, a 72-per-cent higher risk of kidney failure and a 26-per-cent higher risk of depression.
Dr. Muhlestein said the results suggest people can lower their "chances of dying or having heart attacks or developing diabetes" through vitamin D supplementation.
The findings were presented today at the American College of Cardiology's annual scientific session in Atlanta.
Previous studies have found associations between low vitamin D readings and cancer and other chronic ailments, but these new findings are some of the most provocative, because they involved such a large survey of patients.
Detecting different disease risks in such a large group allowed the researchers to conclude that their results were statistically significant, meaning they were unlikely to be flukes due to chance.
But the findings of health benefits from so-called observational studies - such as the one at Intermountain - that compare people based on vitamin D levels have been greeted cautiously within the medical community because they don't actually prove that a lack of the nutrient caused any of the diseases.
Those with more vitamin D could have been living healthier lifestyles involving more outdoor exercise, for instance, explaining why they have lower heart attack risk.
To test whether vitamin D played an active role, the Utah researchers then tracked for a year a group of 9,400 patients who'd been told they needed to take more of the nutrient.
Among the 47 per cent who reached normal vitamin D readings, there was about a 30 per cent reduction in the risk of death and about a 17 per cent reduction in risk of coronary artery disease, suggesting that the nutrient, rather than lifestyle differences, caused the better outcome.
Low blood levels of the vitamin is a common condition among people in high-latitude areas of the world, such as the northern United States and Canada. During fall and winter's feeble sunlight, it isn't possible to make the nutrient the natural way: in bare skin exposed to strong ultraviolet light.
The link to light is the reason the nutrient is dubbed the sunshine vitamin, although small amounts are found in fortified foods, such as milk, and naturally in oily cold-water fish such as salmon. Larger amounts are contained in over-the-counter vitamin supplements.
The survey found that the lowest disease risks occurred among those with blood levels of about 107 nanomoles a litre.
Dr. Muhlestein said people vary widely in the amount of vitamin D needed to reach blood levels associated with lower disease risks. Some required only 1,000 International Units daily, while others needed up to 5,000 IU a day.
These amounts are substantially more than what Health Canada currently advises - 200 to 600 IU a day, depending on age - a recommendation based on the nutrient's well documented role in good bone health. Health Canada and the U.S. government have jointly asked an expert panel whether this recommendation needs to be updated. A decision is expected in July or August.
Dr. Muhlestein isn't waiting. "My recommendation to all my patients, and certainly I did it for myself, is to get your vitamin D checked and if you're very low or even a little bit low, start taking supplementation and then get it rechecked," he said.
Intermountain is a non-profit medical organization with 20 hospitals and other health facilities.
According to figures from the Heart and Stroke Foundation of Canada, cardiovascular disease causes about 31 per cent of all deaths in Canada, or more than 71,000 annually.