The yellow carotenoid lutein has been eyed very closely by researchers in recent years, and is a common ingredient found in a number of dietary supplements, foods and beverages. The majority of lutein found in supplements and foods is extracted from marigold flower petals. An underappreciated and overlooked cousin of lutein is zeaxanthin , which is also found in marigold petals, and like lutein has a keen affinity for certain structures of the eye (lens, retina).
The "hot spot" where lutein and zeaxanthin localize in the eye is called the macula , the center of the retina where light-induced damage and free radical/oxidative damage may occur. Interestingly, at the center of the macula, zeaxanthin is present in concentrations that are double that of lutein, which reverses as one moves away from the center.
Together, lutein and zeaxanthin are the only two carotenoids that comprise the "macular pigment" (MP), which is influenced by both foods and supplements rich in either or both carotenoids. Supplementation with equal doses of either lutein or zeaxanthin alone can produce similar increases in MP, with no apparent difference between the two. The MP can be viewed as sunglasses for blue light (part of the light spectrum that the eye encounters), which penetrates the eye compartment and strikes the macula.
Evidence is mounting that suggests MP can protect against chronic degenerative eye conditions like age-related macular degeneration (AMD) and cataracts. Several studies where blood lutein and zeaxanthin concentrations were measured among people with either condition have drawn a link between low blood concentrations and higher risk. Two recent small-scale studies followed people with cataracts or macular degeneration for 2 years. These subjects were assigned to receive either vitamin E or lutein esters supplements. Only those receiving the lutein esters showing improved visual function (reduced glare sensitivity and increased visual acuity).
A different study gave a supplement containing crystalline lutein and zeaxanthin to subjects with AMD over 12 months and found improvement in recovery from exposure to glare and contrast sensitivity. Additional studies focusing upon the effectiveness of lutein and zeaxanthin in both the prevention and treatment of ocular diseases may yield a new view on evidence-based eye health.