Lutein is an antioxidant carotenoid that occurs in nature, such as dark green leafy vegetables, with zeaxanthin, a closely related carotenoid. Lutein and zeaxanthin concentrate in the eye's macula and lens, as well as in the skin, breast and cervical tissues. Both lutein and zeaxanthin protect the macula from the degradation normally associated with aging and oxidative stress. The macula is responsible for focus and color differentiation. While the average American intake of lutein is only 2 mg per day, other population groups consume from 6 to 20 mg per day.