The ultimate portable health food, apples really do keep the doctor away, suggest researchers at Cornell University, because they contain some of the highest levels of the flavonoid quercetin, a potent antioxidant plant pigment. Red apples provide the most. Flavonoidrich foods also have antiviral, antibacterial and anti-inflammatory effects, and seem to protect against heart disease, stroke, bowel cancer, and Alzheimer�s disease. Make sure you eat the skin, where flavonols concentrate.