Antioxidants protect cells from free radicals, which are byproducts of metabolism that can damage cells. The body produces antioxidants, but also obtains them from foods like green tea, berries, dark chocolate, and fish. Important dietary antioxidants include vitamins A, C, and E, flavonoids, and selenium, which help manufacture glutathione to protect cells from oxidative damage and reduce chronic disease risk. Maintaining adequate antioxidant intake through fruits and vegetables is essential for health.