Lutein And Zeaxanthin For Age-Related Macular Degeneration
Of the 20 observational studies assessed by this systematic review, 13 found that the carotenoids lutein and zeaxanthin might prevent or alleviate age-related macular degeneration.
The retina is the light-sensitive tissue at the back of the eye. The macula is the area of the retina with the highest concentration of photoreceptor cells, and thus a key factor in visual acuity.
Age-related macular degeneration (AMD) occurs when plaque deposits known as drusen start accumulating in the retina, though whether they cause AMD or are just a marker of the disease is unknown. As AMD progresses, the deposits expand and the macula becomes damaged, which can result in blurred vision (particularly in the center field of view), loss of color perception, difficulty seeing in low light, and in the end, blindness.
Lutein and zeaxanthin are carotenoids — a class of plant pigments — present notably in dark leafy greens. Once ingested, they appear to gather in the retina (lutein is dispersed throughout the retina; zeaxanthin concentrates in the macula). This finding in the late 1980s led to the hypothesis that these two carotenoids may benefit eye health. Since then, observational studies have noted an association between dietary intakes of lutein and zeaxanthin and a lower risk of AMD. Intervention trials, however, have produced mixed results. The systematic review summarized below assessed the available evidence.
This systematic review of 55 studies assessed the effect of dietary lutein, zeaxanthin, and meso-zeaxanthin (a metabolite of lutein and zeaxanthin) on AMD.
Of the 20 observational studies, 8 were prospective cohort studies (lasting 5–26 years) and 12 were either case-control or cross-sectional studies.