Consuming foods such as dark green leafy vegetables rich in lutein and zeaxanthin may reduce the risk of late-stage age-related macular degeneration (AMD), according to a new Chinese review of six prior studies. The compounds, both carotenoids, seem to protect the eyes by filtering out harmful blue light that can damage vision cells.
In the new analysis, Peking University researchers combined data only from studies of dietary intake of lutein and zeaxanthin, not those involving supplements. Both carotenoids were associated with a 26% reduction in the risk of late-stage AMD. The pooled results showed only a nonsignificant 4% reduction in risk of early-stage AMD, however.
Dietary sources of lutein and zeaxanthin include such vegetables as spinach and other dark leafy greens, broccoli, zucchini, Romaine lettuce, corn and peas, along with egg yolks.
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The nutrients have been associated with benefits for eye health since 1994, when Harvard researchers identified an association between vegetables such as spinach and lower risk of AMD. Lutein and zeaxanthin provide the yellow pigmentation in the macula, a small spot in the center of the retina of the eye. Over time, with aging, levels of these pigments naturally decrease. The yellow color blocks blue light, so as that pigmentation fades, more of this harmful light can penetrate the eye, damaging the rods and cones used in vision.
The most common (dry) form of AMD occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye. AMD is the leading cause of vision loss in older Americans. Noting that only a few studies have examined the association between the carotenoids and AMD risk, the Peking University scientists called for further research to provide definitive conclusions.
Chung-Jung Chiu, DDS, PhD, a scientist in Tufts HNRCA Nutrition and Vision Laboratory, agrees. I do not consider this as conclusive about the issue, he comments. Currently, what this issue needs is data from a large-scale clinical trial.
TO LEARN MORE: British Journal of Nutrition, online first. National Eye Institute www.nei.nih.gov.