Flavones and flavonols linked to lower kidney cancer risk
flavonols could cut the risk of kidney cancer by 32 and 31 per
cent, respectively, says a new study from Italy.
More than 80 per cent of all kidney cancers are accounted for by renal cell carcinoma (RCC). According to the charity Cancer Research UK, kidney cancer is the tenth most common form of the disease, with a male:female incidence ratio of 5:3. In the UK alone, around 6,600 new cases of kidney cancer are diagnosed each year, and the disease results in around 3,600 deaths.
Age, sex, obesity, smoking and several genetic and medical conditions are believed to be risk factors, but epidemiological data to support the role of diet in kidney cancer aetiology have yielded mixed results.
The multi-centre case-control study, published in the Cancer Epidemiology Biomarkers & Prevention, assessed the dietary intakes of 767 renal cell cancer patients (494 men and 273 women) and 1,534 controls (988 men and 546 women) using a 78-item food frequency questionnaire (FFQ) from which micronutrient intakes were calculated.
The researchers, led by Cristina Bosetti from Milan's Istituto di Ricerche Farmacologiche, "Mario Negri", then applied published data to calculate the six major classes of flavonoids - isoflavones, anthocyanidins, flavan-3-ols, flavanones, flavones, and flavonols - from the participant's food and beverage intake.
After adjusting the results to eliminate possible confounding factors, such as age, BMI, sex, smoking habits and alcohol consumption, the researchers calculated that the highest intake of total flavonoids was associated with a 20 per cent reduction in the risk of RCC, compared to the lowest intake of all flavonoids.
Amongst the individual flavonoids, the biggest protective effect was associated with high intake of both flavones (32 per cent risk reduction) and flavonols (31 per cent risk reduction).
Increased intake of the other classes of flavonoids was also associated with RCC risk reduction, but less pronounced than flavones and flavonols - 24 per cent for isoflavones, 23 per cent for flavan-3-ols, 10 per cent for flavanones, and six per cent for anthocyanidins.
"Allowance for vegetable and fruit consumption only partly explained these inverse relations," wrote Bosetti. "Thus, flavonoids, and particularly flavones and flavonols, may account, at least in part, for the favorable role of plant foods on RCC."
The study does have several notable limitations, including relying on food frequency questionnaires to gather dietary information. FFQs are susceptible to recall of the subjects. It is also not known if cases adjusted their diet after diagnosis of their disease.
Interest in flavonoids is growing rapidly and a mounting body of science, including epidemiological, laboratory-based and randomised clinical trials, continues to report the cancer-fighting potential of a number of different flavonoids, such as isoflavones, anthocyanidins and flavonols.
According to Business Insights, the market potential for flavonoids in the dietetic and nutritional supplement market is in excess of €670m ($862m) for 2007, with annual increases of 12 per cent.
Source: Cancer Epidemiology Biomarkers & Prevention Volume 16, Number 1, Pages 98-101 "Flavonoids and the Risk of Renal Cell Carcinoma" Authors: C. Bosetti, M. Rossi, J.K. McLaughlin, E. Negri, R. Talamini, R. Talamini, P. Lagiou, M. Montella, V. Ramazzotti, S. Franceschi, C. La Vecchia
