Cancer Foundation Blog

Vitamin D and Cancer Prevention

Most people are aware that Vitamin D is the ‘sunshine vitamin’, and we make this critical vitamin after exposure to the sun.  However, even in the summer, 66-68% of Canadians do not have sufficient levels of Vitamin D.

Common sense would tell us that our levels drop in the fall, when our exposure to the sun is limited.  And drop they do, quite dramatically.  Several studies suggest that approximately 95% of Canadians lack adequate vitamin D in the fall.  That’s an astounding number and should make everyone realize how important it is to be taking their daily vitamin D supplement, particularly when several forms of cancer, including breast, ovarian and colon, are linked to vitamin D deficiency, as well as cardiovascular disease, osteoporosis, and stroke.

So how much vitamin D should you be taking to maximize the health benefits from this key nutrient?  Currently, most organizations, including the Canadian Cancer Society, recommend only 1000 IU. 

However, a charitable organization called GrassrootsHealth (http://www.grassrootshealth.net/) has gathered the opinions of sixteen prominent vitamin D researchers and physicians in the United States and Canada – and they recommend an intake of 2000 IU of vitamin D3 per day (Vitamin D3, also called ‘cholecalciferol’, is the type of vitamin D you should be looking for in a supplement).  These scientists firmly believe, as do I, that this amount is safe, and is absolutely necessary to achieve ‘sufficient’ levels for the majority of the population.  Two thousand IU is also the upper limit that the United States’ National Academy of Sciences, Institute of Medicine regards as having no adverse health effects.

A review article published last year in Annals of Epidemiology, suggests that by raising oral intake of vitamin D3 to 2000 IU per day that approximately 58,000 new cases of breast cancer and 49,000 new cases of colorectal cancer would be prevented in Canada and the United States each year.

The importance of adequate levels of vitamin D is further demonstrated by a study of five hundred and twelve women living in Toronto, who had been diagnosed with breast cancer. These women had their vitamin D levels measured and then were followed up to determine outcomes.  The results, published in 2009 in the Journal of Clinical Oncology, showed that women with deficient vitamin D levels were more likely to experience a distant recurrence or die compared to those with sufficient levels of the vitamin.

Did you take your vitamin D today?