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Prevention of colorectal cancer: more time in the sun?
Freedman DM, Looker AC, Chang S-C, Graubard BI. Prospective study of serum vitamin D and cancer mortality in the United States. J Natl Cancer Inst 2007;99:1594–602.
Vitamin D reduces cell proliferation, promotes apoptosis and increases cell differentiation so may have a role in preventing cancer. Photochemical synthesis in the skin is a major source of vitamin D and the risk of many cancers (including colorectal cancer (CRC)) is inversely related to markers of exposure to sunlight. This hypothesis was tested utilising data from the NHANES III study. There were 16 818 participants with 146 578 person-years of follow-up. Serum 25-hydroxyvitamin D (25(OH)D) was measured at baseline by radioimmunoassay. There were 536 cancer deaths during follow-up and no overall association between cancer risk and baseline vitamin D was found. There were 66 CRC deaths and the risk of CRC was inversely proportional to 25(OH)D levels. There appeared to be a dose–response relationship and there was a 72% risk reduction (95% CI, 32% to 89%) in subjects with ⩾80 nmol/l 25(OH)D compared with those with <50 nmol/l. This is a large well designed prospective study but there were multiple analyses conducted on these data so …