Vitamin D helps strengthen your bones, maintain your nervous system, move your muscles and boost your immune system. Whether it also can help protect you against cancer is not entirely clear. But the American Cancer Society says that after numerous studies, there's some promising evidence that vitamin D may play a role in reducing risks for some kinds of cancer.
Vitamin D Sources and Requirements
Vitamin D's best-known function is maintaining bone strength by helping your body to absorb calcium. You produce vitamin D on your own when your skin is exposed to direct sunlight, and you also take it in through foods -- mostly through milk, cereal, juices and other foods that have been fortified with the nutrient. According to the National Institutes of Health, adults need at least 600 IU of vitamin D per day from the ages of 19 to 70, and 800 IU at age 71 and older.
Studies on Colon and Breast Cancer
According to the National Cancer Institute, some studies have found that higher levels of vitamin D were linked to reduced risk of colorectal cancer. But the NCI judges the data inconsistent -- for example, one large study found a reduced risk for men but not for women, and in other studies, the lowered risk was not statistically significant. Research on vitamin D and breast cancer risk has yielded conflicting results, according to the NCI.
Deficiences Common
An M.D. Anderson Cancer Center report -- while stressing that more research is needed -- states that vitamin D may be linked to reduced risk for more than 16 types of cancer, including bladder, breast, colon, endometrial, esophageal, gallbladder, lung, ovarian, pancreatic, prostate and lymphoma. The report says vitamin D deficiency is prevalent and urges people to have a blood test to check whether they are getting enough.
Recommendations
The National Cancer Institute calls vitamin D's possible protective value inconsistent and says some studies suggest a link between higher vitamin D and greater risk for some cancers. Getting more sun is not recommended because of the increased risk of skin cancer. However, talk to your doctor about supplements if you are at high risk for a vitamin D deficiency -- for example, if you are older, have dark skin, are obese or have Crohn's disease.
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