Vitamin D, believed to be useful to protect against cancer by many people, may not be a strong anti-cancer agent except for colon cancer, according to a new study published in the Journal of the National Cancer Institute in Bethesda, Maryland.

"Over the past several years, a number of publications have suggested that vitamin D can reduce deaths from various forms of cancer," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "This is a further bit of evidence that leads us to call for further investigations before we make recommendations for the general population."

Dr. D. Michal Freedman, from the National Cancer Institute in Bethesda, Maryland, and his colleagues analyzed data from the third national Health and Nutrition Examination Survey to examine the relationship between levels of circulating vitamin D in the blood and cancer mortality in a group of 16,818 participants aged 17 and older.

After about a decade of follow-up, 536 participants had died of cancer. Cancer mortality was not related to the level of circulating vitamin D for the overall group, nor was it related when the researchers looked at the data by sex, race, or age.

The only possible exception is that high blood levels of vitamin D do seem to correlate with a reduced risk of death from colon cancer.

An editorial published with the study, written by experts including Johanna Dyer, DSc, RD, of the Office of Dietary Supplements at the National Institutes of Health, states that "the relationship between nutritional factors and colorectal as well as other cancers is complicated" and that the findings "must be put into the context of total diet and lifestyle."

(Agencies via Xinhua News Agency October 31, 2007)