Vitamin D May Lower Colon Cancer Risk

Study Shows Higher Blood Levels of Vitamin D Linked to Reduced Risk of Colorectal Cancer

By Kelli Miller Stacy
WebMD Health News

Reviewed By Brunilda Nazario, MD

Jan. 21, 2010 -- Soaking in more sunlight and drinking more dairy may help you ward off colon cancer.

Researchers in Europe have found that people with abundant levels of vitamin D -- the so-called sunshine vitamin -- have a much lower risk of colon cancer. The findings add to a growing body of evidence that suggest vitamin D may have the power to help prevent colon cancer and possibly even improve survival in those who have the disease.

The body makes vitamin D after the skin absorbs some of the sun's rays. You can also get vitamin D by consuming certain foods and beverages, such as milk and cereal, which have been fortified with the vitamin, but few foods naturally contain it.

For the current study, researchers looked at the link between blood levels of vitamin D as well as dietary vitamin D and calcium, and who was at risk for colorectal cancer. They based their findings on information from the European Prospective Investigation into Cancer Study (EPIC), a study of more than 520,000 people from 10 Western European countries. The study participants gave blood samples and completed detailed diet and lifestyle questionnaires between 1992 and 1998.

During the follow-up period, 1,248 patients were diagnosed with colorectal cancer. Researchers compared their lifestyle and diet backgrounds to the same number of healthy patients. They discovered that those with the highest blood levels of vitamin D had a nearly 40% decrease in colorectal cancer risk than those with the lowest levels.

However, the best way to boost your vitamin D level may be a matter of debate. As vitamin D's potential health benefits become more widely advertised, more people may advocate supplementation. However, the researchers say it's unclear if supplements are better at increasing blood levels of vitamin D than a balanced diet and moderate exposure to outdoor sunlight. They caution that the long-term effects of taking large doses of vitamin D supplements have not been well studied.

"Our findings suggest that the potential cancer risk benefits of higher vitamin D levels should be balanced with caution for the toxic potential," they write in today's online version of BMJ. "Before any public health recommendations can be made for vitamin D supplementation, new randomized trials are needed to test the hypothesis that increases in [blood levels of vitamin D] are effective in reducing colorectal cancer risk without inducing serious adverse events."

Colorectal cancer is the third most common cancer in men and women in the U.S., according to the American Cancer Society.

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SOURCES: News release, BMJ.

Jenab, M. BMJ, Jan. 20, 2010; vol 340.

American Cancer Society web site: "How Many People Get Colorectal Cancer."

National Institutes of Health web site: "Dietary Supplements: Vitamin D."

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