Does vitamin D fight colon cancer?

Medical experts are linking high levels of vitamin D to a reduced risk of colorectal cancer. Researchers looked at blood samples of more than 900 adults who participated in a long-term study. Within the group, 318 people subsequently developed cancer and 624 did not. Those with higher levels of vitamin D in their systems had a lower-than-average risk of developing colorectal tumors. Vitamin D may act by boosting the immune system to recognize and attack cancer cells, say researchers. You can get vitamin D from sun exposure, fatty fish, eggs and fortified foods and beverages such as milk and breakfast cereal.

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Your colon may not ever get to go sunbathing at the beach, but it sure does love an ample supply of the sunshine vitamin.

In a study, people with the highest blood levels of vitamin D -- the nutrient your body synthesizes when exposed to sunlight -- were 40% less likely to develop colon cancer compared with people who had the lowest blood levels of D.

In your body, D seems to play a zone defense against cancer. Laboratory studies suggest it nudges out-of-control cancer cells toward apoptosis -- a natural, programmed cell death designed to eliminate trouble. Vitamin D also slows down cancer-cell reproduction and may even block the growth of blood vessels that supply tumors. 
Dariush Mozaffarian, MD
Internal Medicine
Vitamin D appears to protect against colon cancer in observational studies. For example, a cross-sectional study of 3,121 adults ages 50 and older found that those with the highest vitamin D intakes (more than 645 IU per day) were less likely to have cancerous lesions detected via colonoscopy than those with lower intakes. An analysis of 16,618 participants in the National Health and Nutrition Examination Survey (NHANES) nutrition survey found a relationship between vitamin D status and colon cancer, but not total cancer.

As for the potential increase in skin cancers due to ultraviolet B (UVB) exposure in an effort to generate vitamin D, it's worth noting that the vast majority of skin cancers are not fatal, and some analyses suggest that any increase in skin cancer from adding a small amount of unprotected sun exposure would be offset by declines in other forms of cancer.
Researchers at Dana-Farber/Brigham and Women's Cancer Center found that patients diagnosed with colon cancer that had abundant vitamin D in their blood have better survival rates than those who were deficient in the vitamin. Previous research had shown that higher levels of vitamin D reduce the risk of developing colon and rectal cancer by about 50 percent, but the effect on outcomes wasn't known. Recent data also show that patients with stage IV colon and rectal cancer have very low levels of vitamin D.
Studies have shown that getting an adequate amount of calcium and vitamin D in the diet or from supplements can reduce the risk of polyps. Ongoing studies evaluating the role of vitamins and other natural products are underway to examine their role in colorectal polyp prevention. Although few studies have been able to show definitively that modifying lifestyle reduces the risk of colorectal polyps or cancer, lifestyle changes such as reducing dietary fat, increasing intake of fruits and vegetables, ensuring adequate vitamin and micro-nutrient intake, and exercise, will all improve general health. Regardless of your dietary and lifestyle habits, screening for colorectal polyps is the key in preventing colorectal cancer.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Vitamin D helps fight colon cancer by helping to spur apoptosis, or the destruction of damaged cells, in the body. When cells are damaged, they “commit suicide." Vitamin D helps remind these bad cells to self-destruct.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.