Flavonoids Linked to 20% Lower Kidney-Cancer Risk

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EAT YOUR GREENS--and your purples and yellows, too. Brightly colored fruits and vegetables are already known to contain a wide range of healthful nutrients. Now a new Italian study says that increased intake of flavonoids--antioxidant components found in abundance in such foods--could lower your risk of kidney cancer by nearly a third.

The study, published in the journal Cancer Epidemiology Biomarkers & Prevention, assessed the dietary intakes of 767 renal-cell cancer (RCC) patients and 1,534 controls, with about a third more men than women in each group, and studied their responses to a 78-item food-frequency questionnaire. From this data, the researchers, led by Cristina Bosetti, MD, from Milan's Istituto di Ricerche Farmacologiche "Mario Negri," calculated the subjects' micronutrient intakes. They then applied published data to determine the levels participants were getting of the six major classes of flavonoids: isoflavones, anthocyanidins, flavan-3-ols, flavanones, flavones and flavonols.

After controlling for factors like age, sex and lifestyle potentially associated with RCC risk, the researchers calculated that the highest intake of total flavonoids overall was associated with a 20% reduction in the risk of RCC, compared to the group with the lowest intake of all flavonoids.

And when they broke the flavonoids into major classes, two in particular were found to have the greatest protective benefit: Flavones lowered RCC risk by 32% and flavonols by 31%. The other classes of flavonoids also were associated with reduced RCC risk reduction, but to a lesser degree than flavones and flavonols.

Flavonoids are naturally occurring plant pigments, the brightly colored chemical constituents found in most flesh fruits and vegetables. Several thousand different flavonoid compounds have been identified, the differences between them determined by chemical composition at the molecular level.

Flavone-rich foods include parsley, thyme, celery and hot peppers. Different varieties of flavonols are found in abundance in yellow onions, scallions, kale, broccoli, apples, berries, teas, red grapes and red wine. Other studies have shown that antioxidant flavonoids may offer protection for the heart and may slow or prevent macular degeneration, causing a rise in the popularity of flavonoid supplements. But rather than a rush to the vitamin aisle, Dr. Bosetti recommends a trip to the produce department.

"It is generally believed that intake of nutrients from foods is better than supplementation for cancer prevention," she says, adding that randomized studies of supplemented beta-carotene, for example, "did not provide satisfactory evidence of a benefit."

The American Cancer Society estimates there will be more than 51,000 new cases of kidney cancer this year in the US alone, with about 12,890 people dying from the disease. In general, men are at a higher risk than women.

TO LEARN MORE: Cancer Epidemiology Biomarkers & Prevent/on, Jan. 1, 2007; abstract at .

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