Objective: To examine the role of six flavonoid classes (flavanones, flavan-3-ols, flavonols, flavones, anthocyanidins and isoflavones) and vitamin C in the aetiology of stomach cancer.
Methods: Case-control study undertaken in Greece in the 1980s. Dietary information was obtained from 110 patients with incident stomach adenocarcinoma and 100 control patients. Flavonoid estimates were based on the recently released database of the US Department of Agriculture.
Results: In models including sociodemographic variables, energy intake, vegetables, fruits and, alternatively, vitamin C the six flavonoid classes, only flavanones and vegetables remained significantly inversely associated with stomach cancer risk. The odds ratio (95% confidence intervals) per one standard deviation increase of intake of flavanones was 0.55 (0.31-0.96) whereas for vitamin C it was 1.05 (0.46-2.41). When fruits and vegetables were not adjusted for, both vitamin C and several flavonoid categories were inversely associated with stomach cancer risk, but these associations could be attributed to other compounds in these foods.
Conclusions: Among the major flavonoid classes studied, only flavanone intake is inversely associated with stomach cancer risk and could account for the apparent protective effect of fruit intake against this form of cancer. Additional factors, however, are likely to be involved in the consistent protection conveyed by vegetables.