Protective effect limited mainly to current smokers, Danish study finds.

Dietary beta-carotene is associated with a reduced risk of urothelial carcinoma (UC), especially among current smokers, according to a large Danish study.

Nina Roswall, MSc, of the Danish Cancer Society’s Institute of Cancer Epidemiology in Copenhagen, and collaborators studied data from 55,557 participants in the Danish Diet, Cancer and Health Study. Subjects were aged 50-64 years and had no previous cancer diagnosis. At baseline, individuals completed a detailed food frequency questionnaire.

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During a median 10.6 years of follow-up, 322 cases of UC were diagnosed. Each 5,000-μg increment in dietary beta-carotene intake was associated with a significant 18% reduced risk of UC, the investigators reported in European Urology (2009; published online ahead of print). And each 5,000-μg increment in total beta-carotene intake was associated with a borderline significant 15% decreased risk.

Supplemental beta-carotene use was not associated with UC risk, but the researchers noted that supplemental beta-carotene was not widely used by members of the cohort. The study also found no association between UC risk and dietary, supplemental, or total vitamin C, E, and folate.

When the researchers looked at the association between nutrient intake and UC risk according to smoking status (never, former, and current smokers), they found that beta-carotene significantly lowered UC risk only in current smokers, in whom dietary and total intake of the nutrient was associated with a 34% and 33% decreased risk of UC.