| NEW YORK
NEW YORK (Reuters Health) - Contrary to what many people believe, vitamin D may not be a strong anti-cancer agent, the results of a new study suggest.
The one possible exception is colon cancer: high blood levels of vitamin D do seem to correlate with a reduced risk of death from this cancer.
"This study was the first, to our knowledge, to look at the relationship between measured vitamin D in blood and subsequent total cancer (deaths) in a population," lead author Dr. D. Michal Freedman, from the National Cancer Institute in Bethesda, Maryland, told Reuters Health.
"The key finding was the lack of an association between vitamin D levels in the blood and subsequent total cancer risk. We were uncertain what association we would find, partly because there were no previous studies that had looked at overall cancer mortality after vitamin D blood measurements," he added.
The findings, which appear in the Journal of the National Cancer Institute, are based on an analysis of data for 16,818 subjects who participated in the Third National Health and Nutrition Examination Survey. The subjects were at least 17 years of age when the survey was undertaken between 1988 and 1994 and they were followed through 2000. Vitamin D levels were measured with a standard test when the study began.
During the study period, 536 cancer deaths occurred, the report indicates. As noted, no association between vitamin D levels and total cancer deaths was apparent. This held true in the overall analysis as well as in analyses confined to various ethnic and age groups.
By contrast, there was some evidence that vitamin D may help prevent colon cancer. In the study, people with the highest vitamin D levels were 72 percent less likely to die from this cancer than were people with the lowest levels.
"Among the questions to be addressed in future studies is the relationship between vitamin D levels and future cancer risk both for individual cancer sites and for total cancer risk." The NCI and other institutes currently have a number of these studies underway, Freedman said.
In a related editorial, Dr. Cindy D. Davis, from the NCI, and Dr. Johanna T. Dwyer, from Tufts University in Boston, comment that "while vitamin D may well have multiple benefits beyond bone, health professionals and the public should not in a rush to judgment assume that vitamin D is a magic bullet and consume high amounts of vitamin D."
SOURCE: Journal of the National Cancer Institute, November 7, 2007.