In addition to vitamins C and E, the most common and active antioxidant compounds that occur naturally in foods are flavonoids. Dietary flavonoids are highly bioavailable, and have been shown to confer antioxidant protection, inhibit platelet activation, exert vasorelaxant effects, and reduce inflammation in human studies. In animal model studies, dietary flavonoids have been shown to reduce the development of atherosclerosis. Polyphenols also have potent antibacterial, antifungal, and antiviral activities.