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Reviewed By Louise Chang, MD
Vitamin D has attracted attention from researchers for its possible anticancer effects.
Freedman's team studied data on more than 16,800 people aged 17 and older who participated in U.S. health studies between 1988 and 1994.
In those studies, participants got a blood test to measure their blood level of vitamin D.
Freedman and colleagues followed the participants through 2000. During those 12 years, 536 participants died of cancer.
Participants' vitamin D levels at the study's start didn't appear to affect cancer mortality in general, regardless of age, sex, race, or other factors.
However, people with high levels of vitamin D at the study's start were 72% less likely than those with low levels of vitamin D to die of colorectal cancer.
Death rates for the other cancers that were studied, including lung cancer, breast cancer, prostate cancer, other digestive cancers, non-Hodgkin's lymphoma, and leukemia, weren't linked to vitamin D blood levels.
The study's limits include the fact that participants only had their vitamin D level checked once. So it's not clear if their vitamin D level rose or fell over the years.
Freedman's team had lots of data including which participants smoked and exercised. But they can't rule out the possible influence of other factors.
The study appears in next week's edition of the Journal of the National Cancer Institute.
An editorial published with the study 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."
The editorial was written by experts including Johanna Dyer, DSc, RD, of the Office of Dietary Supplements at the National Institutes of Health (NIH).
SOURCES: Freedman, D. Journal of the National Cancer Institute, Nov. 7, 2007; vol 99: pp 1594-1602. WebMD Health News: "Vitamin D for Cancer Prevention?" Davis, C. Journal of the National Cancer Institute, Nov. 7, 2007; vol 99: pp 1563-1565. News release, Journal of the National Cancer Institute.
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