Lutein

Lutein is an oxygenated carotenoid, a member of the xanthophyll group, with the formula C40H56O2. Like other carotenoids it is fat-soluble and is produced only by plants, algae, and some microorganisms; animals, including humans, obtain it from the diet. Lutein is closely related to zeaxanthin, its structural isomer, and the two can be converted into a third form, meso-zeaxanthin, within the eye.

Dietary sources are led by dark green leafy vegetables such as spinach and kale, along with corn, egg yolk, and various peppers. Commercially, lutein is extracted from the petals of the marigold Tagetes erecta. In this role it is approved in the European Union and some other regions as the food colorant E161b, while the United States permits it in dietary supplements and animal feed rather than as a color additive for human food.

The best-studied role of lutein is in the eye, where it and zeaxanthin build up in the macula to form the macular pigment, filtering high-energy blue light and acting as antioxidants. Evidence on supplements is mixed. A systematic review and meta-analysis found that higher dietary intake of lutein and zeaxanthin was associated with a lower risk of late age-related macular degeneration, though not of early disease ^[3]. In the large AREDS2 trial, adding lutein and zeaxanthin to an eye-health formulation did not by itself significantly reduce progression to advanced macular degeneration, but the carotenoids proved a safer replacement for beta-carotene, which had raised lung cancer risk in former smokers ^[4]. A separate supplementation trial raised blood levels of the carotenoids without significantly increasing measured macular pigment density over placebo ^[1].

Lutein also crosses into the brain, and higher lutein status has been associated with measures of cognitive performance from childhood through older age, although this research remains preliminary ^[2]. It is commonly sold as a supplement, often paired with zeaxanthin, and because it is fat-soluble its absorption improves when taken with a meal containing fat. There is no established recommended dietary allowance.

Lutein is very safe and well tolerated even at high intakes; the worst common effect is harmless yellowing of the skin (carotenodermia) at very high doses. It has no known serious interactions. Food and supplement sources both appear safe long-term.