NEW YORK (Reuters Health) - Flavonols may have a protective effect against the development of pancreatic cancer, especially for current smokers, according to findings published in the October 15th issue of the American Journal of Epidemiology.

"Flavonols are a class of flavonoids, polyphenols, that are ubiquitous in plant foods and may exert cancer preventive effects," Dr. Ute Nothlings, of the German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, and colleagues write. "However, evidence from human population studies is scarce and has been hampered primarily by a lack of coverage of flavonols, as well as flavonoids in general, in food composition databases."

The researchers used data from the Multiethnic Cohort Study to examine flavonol intake as a risk factor for pancreatic cancer during 8 years of follow-up. The team estimated intakes of three flavonols -- quercetin, kaempferol, and myricetin -- and examined associations with incidence of pancreatic cancer among 183,518 participants.

A total of 529

cases of pancreatic cancer occurred during follow-up. Results of multivariate Cox regression analyses revealed an association between intake of total flavonols and a reduced risk of pancreatic cancer (relative risk for highest versus lowest quintile = 0.77, p = 0.046). Of the three individual flavonols, the largest risk reduction was seen with kaempferol.

An inverse association among current smokers was observed with total flavonols, quercetin, kaempferol, and myricetin (relative risks for highest versus lowest quartile = 0.41, 0.55, 0.27, and 0.55, respectively). No inverse association was found for never or former smokers.

"Smoking increases oxidative stress, and smoke contains a large quantity of carcinogens," Dr. Nothlings and colleagues note. "Therefore, the actions of flavonols as antioxidants or as modulators of the expression of cytochrome P-450 enzymes involved in the activation of carcinogens may explain the larger risk reduction effect in smokers compared with nonsmokers."

Am J Epidemiol 2007;166:924-931.