Posted on March 8th, 2009 by
Researchers from several U.S. medical institutions have reported that higher levels of circulating vitamin D, as well as higher vitamin D intake, are associated with a decreased incidence of colorectal adenomas (polyps) and recurrent adenomas. The details of this combined analysis were published in the November 1, 2008 issue of Cancer Epidemiology Biomarkers and Prevention.
Colorectal cancer is a type of cancer that is highly preventable or curable in early stages through screening. In a majority of cases, colon cancer develops from small growths, or polyps, in the colon called adenomas. The larger the adenoma, the more likely it will eventually become cancerous.
Individuals who have adenomas are at an increased risk of developing future adenomas and also colon cancer. As a result these individuals are encouraged to undergo more stringent screening, such as colonoscopy, during which adenomas are removed to prevent the possibility that they may progress to cancer. In addition, researchers continue to evaluate the role of diet and other preventive factors that may help decrease the incidence of adenomas and colon cancer.
Vitamin D is a fat-soluble vitamin that comes from dietary supplements, foods such as fortified milk and cereal, certain kinds of fish (including salmon, mackerel, and tuna), and exposure to sunlight. Several case-control studies have suggested that calcium and vitamin D supplementation can decrease the incidence of colorectal cancer, especially in high-risk individuals. However, no randomized trial has confirmed these observations.
In the current study, researchers performed a combined analysis of 17 previous studies evaluating circulating vitamin D levels, as well as vitamin D intake. The results of the analysis indicated that individuals with the highest levels of circulating vitamin D had a 30% reduction in the risk of developing adenomas when compared with individuals with the lowest levels of circulating vitamin D. Individuals with the highest vitamin D intake had a 10% reduction in the risk of developing adenomas when compared with the group with the lowest vitamin D intake.
The role of diet in relation to cancer incidence remains a major focus among researchers, and the results of this particular analysis are promising. Individuals with a personal or family history of adenomatous polyps or familial adenomatous polyposis (FAP) may wish to speak with their physician about the risks and benefits of increasing vitamin D intake.
 Wei MY, Garland CF, Gorham ED. Vitamin D and prevention of colorectal adenoma: A meta-analysis. Cancer Epidemiology, Biomarkers and Prevention. 2008;17(11):2958-2969.
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