Does Vitamin D Protect Against Cancer?

Healthnotes Newswire (November 29, 2007)—In the ongoing search for ways to prevent and treat cancer, vitamin D has recently claimed the spotlight. A new study found that having high levels of vitamin D may protect against colon and, possibly, breast cancer. However, it does not appear to change the likelihood of developing other types of cancer.

Vitamin D is most well-known for its important role in calcium regulation and bone health, but new interest in the vitamin has focused on its immune-modulating effects and possible role in cancer prevention.

The body makes most of the vitamin D it needs through a process that involves a reaction between sunlight and skin, but concern about deficiency due to low sun exposure and sunscreen use has been growing. A recent study found that 36% of healthy young adults and 57% of hospitalized adults have low vitamin D levels, and might therefore be at increased risk for osteoporosis, cancer, and other chronic diseases. Even higher rates of deficiency have been seen in the elderly.

The evidence for vitamin D’s anticancer effect is based primarily on research finding that rates of cancer deaths are higher in northern regions that receive less sunlight, and that people diagnosed with cancer in winter months have lower survival rates. These findings encompass a range of cancers including breast, ovarian, prostate, and colorectal.

The new study, published in the Journal of the National Cancer Institute, used data collected for the Third National Health and Nutrition Examination Survey (NHANES III). The 16,818 people had their blood levels of vitamin D measured upon enrollment and were followed for 6 to 12 years.

The rates of death due to cancer were similar in people with high vitamin D levels and people with low levels. When individual types of cancer were considered, only colon cancer risk was related to vitamin D status: people with the highest levels of vitamin D had a 72% lower risk of colorectal cancer than those with the lowest levels. Higher vitamin D levels were also associated with a lower number of deaths due to breast cancer, but the number of breast cancer–related deaths was considered to be too small to be conclusive.

“Our results do not support an association between [vitamin D] and total cancer mortality,” the study’s authors concluded, “although there was an inverse relationship between [vitamin D] levels and colorectal cancer mortality.” They pointed out that the beneficial effect of vitamin D on colorectal cancer risk seen in this study is consistent with findings from a number of previous studies.

(J Natl Cancer Inst 2007;99:1594–602)

Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.

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