Gold onion vegetable bulbsFlavonoids are substances produced by plants that act as antioxidants. Flavonols are a class of flavonoids. Research, appearing in the American Journal of Epidemiology (15 October, 2008; Volume 166, Issue 8, Pages 924-931), shows that flavonols from foods like onions, berries, and apples may protect against cancer. The study (part of the Multiethnic Cohort Study) looked at over 183,000 subjects and their diets. It found that those with the highest consumption of flavonols had a significantly lower risk of developing pancreatic cancer. The reduction in pancreatic cancer was about 25%. Smokers had an even greater benefit, with a 59% reduction in the incidence of pancreatic cancer.