Low levels of lutein and zeaxanthin - carotenoids found in dark green, leafy vegetables such as spinach and kale - could contribute to age-related macular degeneration (AMD), according to researchers who believe they have further evidence to support the theory that the antioxidants can prevent the disease.
The researchers, led by Dr Paul Bernstein at the Department of Ophthalmology and Visual Sciences, Moran Eye Center in the University of Utah School of Medicine in Salt Lake City, said their study shows that AMD patients who had begun taking high-dose lutein supplements (4 milligrams or more per day) regularly after their initial diagnosis of AMD were able return those levels back to normal.
"This research is a major step toward large-scale clinical studies to prove the extent to which lutein and zeaxanthin protect against age-related macular degeneration," Bernstein said. "We know that these carotenoids are specifically concentrated in the macula of the human eye."
The research compared the macular pigment levels of healthy eyes with those eyes of people with AMD. The researchers report that for the first time, they were able to objectively measure lutein and zeaxanthin levels in the eyes of living people in a large clinical study. Bernstein measured macular carotenoid levels in 93 eyes from 63 patients with AMD and in 220 normal eyes from 138 volunteers using resonance Raman spectroscopy.
The researchers found that macular carotenoid levels decline with age, reaching a stable low level after the age of 60, the age when AMD incidence begins to rise dramatically. They also found that macular pigment levels in the eyes of AMD patients not consuming high-dose lutein supplements were 32 per cent lower than elderly normal eyes.
"These results taken together lead us to believe that low macular levels of lutein and zeaxanthin represent a pathogenic risk factor for the development of AMD," Bernstein said. "As a safeguard, patients at risk for visual loss from AMD should consider supplementing their diets with at least 4mg of lutein each day along with other antioxidant nutrients."
The National Eye Institute, Spectrotek, and Kemin Foods, which makes purified lutein, supported the study.