Quercetin May Help Protect Colon From Cancer
Lee Swanson Reserch Update
Increased intakes of the antioxidant flavonoid quercetin, found in onions and apples, may reduce the risk of developing cancer of the colon by 50%, according to a recent study.
However, dietary intakes of the flavonoid were not associated with beneficial effects on rectal health, researchers reported in the British Journal of Nutrition.
Researchers from the University of Aberdeen add that increased intakes of flavonoids in general were associated with a 40% reduction in the risk of developing colorectal cancer.
Flavonoids can be split into a number of subclasses, including anthocyanins found in berries, flavonols from a variety of fruits and vegetables, flavones from parsley and thyme, flavanones from citrus, isoflavones from soy, mono- and poly-meric flavonols like the catechins in tea and proanthocyanidins from berries, wine and chocolate.
In order to examine the benefits of a flavonoid-rich diet with respect to colorectal cancer risk, the researchers performed a case-control study involving 264 people with confirmed colorectal cancer and 408 healthy, cancer-free controls.
Since tea is the main dietary source of flavonoids in the United Kingdom, the researchers sought to distinguish between total dietary and non-tea intake of four flavonoid subclasses—flavonol, procyanidins, flavon-3-ol and flavanone. The participants were drawn from a "tea-drinking population with a high colorectal cancer incidence," said the researchers, led by Janet Kyle.
While no association between total dietary flavonoids and the incidence of colorectal cancer was observed, when Kyle and her co-workers considered only flavonoids from non-tea sources and the specific site of the cancer, a significant protective effect was documented for non-tea flavonols and colon, but not rectal, cancer.
"We concluded that flavonols, specifically quercetin, obtained from non-tea components of the diet may be linked with reduced risk of developing colon cancer," the researchers concluded.
British Journal of Nutrition Published online ahead of print.