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Lutein and zeaxanthin are chemically very closely related to each other; both have the exact same chemical formulae, differing only in their ring stereochemistry and the spatial placement of one end ring and the placement of a double bond in that end ring. Zeaxanthin is a stereoisomer of lutein, differing only in the location of a double bond in one of the hydroxyl groups. The hydroxyl groups appear to control the biological function of these two xanthophylls. Lutein and zeaxanthin are often found together and in esterified form in the same source, although the ratio of lutein to zeaxanthin varies substantially depending on the source.

In people, lutein and zeaxanthin make up most of the pigment in the center of the retina, the central part of the retina responsible for sharp and detailed vision. These two pigments absorb wavelengths in the high-energy spectrum, they may help protect retinal cells in the macula against "phototoxic" damage caused by short-wavelength high-energy light radiation.

Health benefits of lutein and zeaxanthin

Macular degeneration is a medical term that applies to any of several disease syndromes which involve a gradual loss or impairment of eyesight due to cell and tissue degeneration of the yellow macular region in the center of the retina. Age-related macular degeneration (AMD) is the most common form of this type of disease. Lutein serves important roles in vision to help filter ultraviolet wavelengths of light to prevent damage to the eye lens and macula. Lutein has been shown to have significant potential in the prevention of age-related macular degeneration (AMD), the leading cause of irreversible blindness among Americans age 65 and older. Lutein helps build macular pigment density, a critical factor in the health of the macula and the retina. Lutein acts as a natural sunshade, protecting the eye from too much light. Blue light, which has the shortest wavelength on the visible spectrum, is especially damaging to the eye and can cause photo-oxidation in the macula. This can lead to lipid peroxidation, which is toxic to the retina.

In addition to playing pivotal roles in ocular health, lutein and zeaxanthin are important nutrients for the prevention of cardiovascular disease, stroke, and lung cancer. They may also be protective in skin conditions attributed to excessive ultraviolet (UV) light exposure. Lutein and zeaxanthin inhibit lipid peroxidation, a likely factor in the etiology of both retinal and cardiovascular disease. Lutein and zeaxanthin can inhibit thickening of the walls of carotid arteries and LDL-induced migration of monocytes to human artery cell walls. Skin exposure to UV rays generates reactive oxygen species, inflammation in skin cells, and erythema. Lutein and zeaxanthin may prevent cellular damage in these conditions by quenching singlet oxygen or neutralizing photosensitizers. Intake of dietary antioxidants, including lutein and zeaxanthin, reduces this inflammatory response, as carotenoids are poor absorbers of UV light.

Sources of lutein and zeaxanthin

Lutein can be found in the chromoplasts of flowers, fruits and roots (such as, but not limited to, carrots and yellow potatoes). Lutein is typically present in plant chromoplasts as long chain fatty esters, typically diesters, of acids such as palmitic and myristic acids, e.g. lutein dipalminate, lutein dimyristate and lutein monomyristate. Lutein and zeaxanthin is abundant in a number of yellow/orange fruits and vegetables such as mango, papaya, peaches, prunes, acorn squash, winter squash, and oranges. Egg yolks are the richest source and also contain a large amount of zeaxanthin. Although lutein and zeaxanthin may be obtained from certain fruits and vegetables, the isolation of lutein from extracts of marigold flowers and zeaxanthin from berries of Lycium Chinese Mill (LCM berries) proves to be most economical. In Marigold flowers lutein is the major carotenoid and is normally accompanied by about 3-6% zeaxanthin; in LCM berries zeaxanthin is the major carotenoid and is completely free from lutein. In both of these plants, lutein and zeaxanthin are esterified with fatty acids such as lauric, myristic, and palmitic acids.

Dosage and administration

While no recommended daily allowance currently exists for lutein as for other nutrients, positive effects have been seen at levels of 6 mg/day. Individuals who consumed between 6 mg and 12 mg of lutein per day in their diets were less likely to develop cataracts, macular degeneration, and colon cancer. Lutein, in supplemental form, should be taken with fat-containing food to improve absorption.