Vitamin D is crucial for maintaining the health of bones and muscle tissue, and severe deficiencies can lead to debilitating diseases like rickets, which makes bones soft and easy to fracture. Recent studies have also linked inadequate vitamin D levels to increased risk for cancer, diabetes and cardiovascular disease, among other conditions.
In March of this year, Statistics Canada reported that ten percent of Canadians -- or roughly three million people -- had inadequate levels of vitamin D in their blood for optimal health, and fully 1.1 million were vitamin D deficient.
Some researchers have suggested that Canadians are simply not getting enough vitamin D from diet or supplements to compensate for our northern, low-sunlight climate. However, genetic factors are just as important as environmental factors in determining vitamin D levels. This current study is the largest scientific undertaking to identify the genes responsible for low vitamin D levels. Their results will be published June 10 in the influential British medical journal The Lancet.
One of the paper's co-authors is Dr. Brent Richards of the Lady Davis Institute for Medical Research of the Jewish General Hospital, working with lead author Dr. Thomas J. Wang of Massachusetts General Hospital and colleagues all over the world.
"It's long been known that vitamin D levels are strongly determined by genetic factors," said Dr. Richards, an assistant professor at McGill University's Faculty of Medicine. "However, those genetic factors have not been well described in replicated studies."
The authors did a genome-wide association study of 34,000 caucasian people of European descent and were able to positively identify variants at three genetic sites (or "loci") that are significantly associated with vitamin D concentration in the blood.
"Those individuals most at risk had a two to 2.5-fold greater risk of having vitamin D deficiency," said Dr. Richards. "The magnitude of effect of these genes is equal to or larger than taking a vitamin D supplement."
Richards cautions, however, that the study should not encourage people to immediately start taking large doses of vitamin D.
"We need to have a much more thorough understanding of the risk and benefits first," he explained. "We're doing follow-up studies to determine whether or not people who harbour these risk genes need higher doses of vitamin D supplementation. We're also trying to understand if these genes interact with environmental factors such as sunlight exposure and supplement intake.
"Ultimately we want to understand if people with these genes can be protected from the forms of cancer, diabetes and cardiovascular disease associated with vitamin D deficiency by taking supplements."
About the Lady Davis Institute for Medical Research at the Jewish General Hospital
The Lady Davis Institute for Medical Research (LDI), located in Montreal, Quebec, is the research arm at the Jewish General Hospital, and has strong academic ties to McGill University. With over 150 affiliated researchers, the LDI is one of the largest and most important biomedical research institutes in Quebec and all of Canada. Major breakthroughs have been made by LDI researchers in the areas of HIV/ AIDS, aging, cancer, vascular disease, epidemiology and psychosocial science, and have thereby contributed to the health and well-being of millions of patients in Montreal, across Quebec and around the world.
About the Jewish General Hospital
Now in its landmark 75th year of providing Care for All, the Jewish General Hospital has been a mainstay of superior medical care for generations of patients of all backgrounds. One of Quebec’s largest and busiest acute-care hospitals, the JGH is committed to improving the quality of healthcare for all Quebecers in partnership with the provincial healthcare network. In this anniversary year, the Jewish General Hospital has redoubled its commitment providing patients the best possible care in a clean, safe and human-centered environment. The JGH is able to deliver these pioneering, innovative medical services by strengthening its role as a McGill University teaching hospital, by expanding and upgrading its facilities, and by pursuing cutting-edge research at the Lady Davis Institute for Medical Research. Website: jgh.ca