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Flavonoids reduce pancreatic cancer risk among male smokers

By Shane Starling , 21-Mar-2008

Finnish researchers have found flavonoid consumption may cut the risk of developing pancreatic cancer among male smokers.

They scrutinised the responses of 27,000 50 to 69-year-old healthy male smokers to a questionnaire and found "greater total flavonoid intake was associated with decreased pancreatic cancer risk in participants randomised during the trial to placebo…". The findings, published in the March edition of Cancer Epidemiol Biomarkers, are backed by at least three cited studies including a Finnish cohort study involving more than 10,000 people that found reduced rates of pancreatic cancer in both sexes. But the researchers suggested the effect may be compromised by smokers who may have been consuming supplemental A-tocopherol and/or B-carotene. Flavonoids are components of plants that are especially concentrated in fruits and vegetables such as broccoli and other cruciferous vegetables, apples, beans and onions. They have been shown to have various benefits including cancer reduction, heart health and free radical (oxidation) control.


Functional beverages such as superfruit juices have risen to prominence on the back of their boosted antioxidant levels and high-antioxidant food supplements derived from sources such as flax have also become popular with consumers. Flavonoid effects The study examined, "the association between dietary intakes of total flavonoids, three flavonoid subgroups (flavonols, flavan-3-ols, and flavones), seven individual flavonoids (kaempferol, myricetin, quercetin, catechin, epicatechin, apigenin, and luteolin), and flavonoid-rich foods and development of exocrine pancreatic cancer in a prospective cohort of male smokers in Finland." With such a large sample many variables had to be accounted for and these included age; height, weight, and body mass index; education; place of living; self-reported history of diabetes mellitus, pancreatitis, gallstones, or peptic or duodenal ulcers; measured blood pressure; serum cholesterol; smoking habits; occupational and leisure physical activity; energy and alcohol intake; and energy-adjusted fat, saturated fat, carbohydrate, free sugar, fibre, h-carotene, calcium, folic acid, vitamin C, and vitamin E intake.


The researchers acknowledged this variation "could cause inaccurate risk estimates" but noted "the monotonic decreasing hazard ratios across flavonoid intake quartiles and the consistency of the reduced pancreatic cancer risk across individual flavonols and flavan-3-ols among participants in the placebo group would support that subjects were ranked robustly enough to observe associations." After adjustments were made for the above factors it was demonstrated there was a 64 per cent reduced pancreatic cancer risk for those with high total flavonoid intake, relative to low intake, particularly for the flavonol kaempferol and the flavan-3-ol catechin. Inverse trends were observed for three individual myricetin, quercetin, and epicatechin. In the case of quercetin these results supported an Argentinian study that found raised quercetin intake had led to an increased incidence of pancreatic dysplastic foci in rats. But the researchers noted animal studies in pancreatic cancer models backed their conclusions that high dietary intake of flavonols and flavan-3-ols could inhibit human pancreatic carcinogenesis.


Modus operandi The researchers suggested flavonols and flavan-3-ols inhibit pancreatic carcinogenesis via various actions including inhibition of proliferation, cell cycle arrest, induction of apoptosis, promotion of differentiation, antioxidative activity, and inhibition of angiogenesis. But they cautioned: "Our results should be considered with caution given the relative small number of cases in the placebo group and the lack of an established biological mechanism for the interaction that we observed." "Most pertinent, flavonoids can inhibit the activity of phase I enzymes and increase the activity of phase II enzymes," they stated.


The researchers pointed out their conclusions were related to men and not necessarily applicable to non-smokers, women, and populations with high consumption of food supplements. In the United States, pancreatic cancer is the fourth most common cause of cancer mortality. It led to 33,400 deaths among men and women in 2007. Source: Cancer Epidemiol Biomarkers March 2008 Volume 17. Pages 553-62.


Flavonoid Intake and Risk of Pancreatic Cancer in Male Smokers (Finland)


Authors : Gerd Bobe, Stephanie J. Weinstein, Demetrius Albanes, Tero Hirvonen, Jason Ashby, Phil R. Taylor, Jarmo Virtamo, and Rachael Z. Stolzenberg-Solomon

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