Vitamin D Won't Help Prevent Most Cancers

TUESDAY, Oct. 30 (HealthDay News) -- High blood levels of vitamin D did not lower the overall cancer death rate in a long-term study, researchers report.

However, they did note a marked reduction in colorectal cancer deaths linked to the vitamin.

The findings, by a team from the U.S. National Cancer Institute, run counter to some earlier data suggesting that vitamin D might help prevent malignancy.

"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."

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Even the finding that the vitamin might lower colon cancer risk merits further study, added Lichtenfeld, who was not involved in the research. "We have called for further research to see if vitamin D does or does not reduce deaths from cancer," he said. "We do not have sufficient evidence at this time to make a recommendation, for example, that people increase their intake of vitamin D to reduce the risk of colorectal cancer."

In their study, the NCI team looked at data on almost 17,000 participants in the third Health and Nutrition Examination Survey who were followed for anywhere from six to 12 years. There were 536 deaths from cancer in the group during that time.

The study found no relationship between overall cancer deaths and circulating blood levels of vitamin D, said the report, published in the Oct. 30 issue of the Journal of the National Cancer Institute.

However, people with higher levels of circulating vitamin D had a 72 percent lower risk of colorectal cancer mortality than those with lower levels, the report found.

These numbers can't be taken to mean that vitamin D prevents colorectal cancer because the study was not large enough and didn't run long enough to provide definitive information, said Cindy Davis, a program director in the NCI nutrition sciences research group and co-author of an accompanying editorial.