ST. LOUIS--June 9, 2003-- A recent human study from the Medical Research Council Environmental Epidemiology Unit, University of Southampton, U.K. provides scientific evidence that a key nutrient and a strong antioxidant member of the carotenoid family, called zeaxanthin (zee-ah-ZAN'-thin,) may be far more important in preventing or stabilizing macular degeneration than previously realized. Macular pigment, which is primarily composed of lutein and zeaxanthin, is thought to protect the retina from damage due to light exposure and oxidative stress. Additionally, it has been shown that a high macular pigment density helps to retain visual sensitivity as we age and evidence indicates that raising the intake of dietary zeaxanthin can increase macular pigment. The macular pigment acts like "sunglasses" by protecting the critically important central sight from damaging light waves. The distribution of lutein and zeaxanthin in the eye may indicate they have different functions. Zeaxanthin is the dominant component in the center of the macula, while lutein dominates at the outer edges. The eye is selective and preferentially places dietary zeaxanthin in the very center of the macula, the most critical area for central vision with the greatest need for protection. This selective uptake of zeaxanthin occurs even though lutein is more available in the diet by a 20:1 ratio.
Previous investigations may have obscured evidence of zeaxanthin's greater protective role by looking at the two carotenoids together, rather than separately. Although both of these carotenoids protect the retina, zeaxanthin has been shown to be a better photoprotector and a recent animal study supports the photoprotective activity of zeaxanthin. Additionally, zeaxanthin's chemical structure makes it a much more effective antioxidant than lutein. The human study concluded that decreased blood plasma zeaxanthin, but not blood plasma lutein, is significantly associated with the risk of age-related macular degeneration. This correlation strongly indicates that a high level of dietary zeaxanthin intake may directly affect the risk of developing macular degeneration. Increasing intake through diet or supplementation may help to slow down or stop vision loss with those who have been diagnosed with AMD.