Vitamin D Appears Effective in Reducing Colorectal Cancer Incidence
A larger daily dose of vitamin D could reduce the incidence of colorectal cancer with minimal risk, according to a new review that pools results from five studies.
The analysis found that maintaining a specific target blood level of vitamin D was associated with a 50 percent lower risk of colorectal cancer than that seen in people with consistently lower blood levels.
Previous studies had shown that lower blood levels of vitamin D did not protect against colorectal cancer, according to lead author Edward Gorham, Ph.D., a research epidemiologist with the Naval Health Research Center in San Diego. However, a meta-analysis pools the data from several studies, thus increasing the strength of the results.
The study is being published in the March issue of the American Journal of Preventive Medicine.
The five studies looked at serum collected from healthy volunteers who were then followed for periods ranging from two years to 25 years. There were 535 cases in the pooled analysis and 913 controls, or 1,448 total participants.
The researchers found that a blood serum vitamin D level of 33 nanograms per milliliter or higher was associated with a 50 percent lower risk of colorectal cancer than that seen with blood levels of 12 nanograms per milliliter or lower.
Vitamin D levels in the body are a factor of both diet and sun exposure. Exposing the skin to the sun lets the body synthesize vitamin D, which is why mortality due to colorectal cancer may be higher in geographic areas that get less sunshine.
The amount of dietary vitamin D needed to reach the serum levels that appear to be protective against colorectal cancer