Lutein is a type of organic pigment called a carotenoid, which is related to beta-carotene and vitamin A. It is synthesized only by plants and is found in high quantities in green leafy vegetables such as spinach, kale, and yellow carrots. Lutein is important for eye health and is one of two major carotenoids found in the human eye (macula and retina). It is thought to function as a light filter, protecting the eye tissues from sunlight damage. Lutein is commonly taken by mouth to prevent eye diseases, including cataracts and age-related macular degeneration (AMD), which is the leading cause of blindness and vision impairment. Some studies have also reported that lutein may have positive effects in different clinical conditions, thus ameliorating cognitive function, decreasing the risk of cancer, and improving measures of cardiovascular health. Lutein is found in many foods, including egg yolks, spinach, kale, corn, orange pepper, kiwi fruit, grapes, zucchini, and squash. According to the NHANES 2013-2014 survey, adults in the United States consume on average 1.7 mg/day of lutein and zeaxanthin combined. No recommended dietary allowance currently exists for lutein, but some positive health effects have been seen at dietary intake levels of 6–10 mg/day. The only definitive side effect of excess lutein consumption is bronzing of the skin (carotenodermia).