The fear of losing vision as they age has pushed many consumers to try to safeguard their eyesight with vitamins and supplements.
Many of the formulas contain a combination of the antioxidant vitamins C, E and beta carotene, plus the mineral zinc. Some contain lutein and zeaxanthin, yellow pigments that accumulate naturally in the light-sensitive retina and the lens. Still others include such herbs as bilberry and grape seed extract.
Doctors acknowledge that some supplements might help slow or prevent eye disease, but they caution that the evidence for most of them remains largely theoretical.
"There’s nothing wrong with taking a multivitamin or a vitamin with these things in it, but I don’t think we should make firm claims that haven’t been scientifically validated," said Dr. Michael Marmor, a retina specialist at Stanford University in Palo Alto, Calif.
Of the available formulas, those with three familiar vitamins plus zinc have produced the strongest results. In a large seven-year study published in 2001, a high-dose antioxidant cocktail of vitamins C, E, beta carotene and zinc slowed progression and associated vision loss by 25 percent among patients with moderate to advanced macular degeneration. The disease, caused by the incurable breakdown of the macula (the central part of the retina), is the leading cause of blindness in people over 65.
A follow-up study last fall estimated that if the 8 million Americans over 55 who are at high risk for advanced macular degeneration took the supplement, 300,000 fewer people would lose their vision in the next five years. Currently, about 1.7 million Americans have the advanced form.
There’s far less direct evidence for the benefits of lutein and zeaxanthin supplements, although they hold great promise, experts say. The pigments are believed to filter out damaging UV light before it hits the back of the eye, while neutralizing damaging molecules called free radicals.
"With lutein and zeaxanthin, we’re where we were 10 years ago with zinc and other antioxidants," said Dr. Frederick Ferris, clinical director of the National Eye Institute, who led the landmark study on vitamins and zinc. Researchers have found that people who eat lots of foods rich in lutein and zeaxanthin are less likely to develop advanced macular degeneration and might also get some protection against cataracts.
Doctors now advise patients to consume plenty of lutein-containing leafy green vegetables such as spinach, kale and collard greens, as well as yellow and orange fruits and vegetables. They also recommend wearing sunglasses to protect eyes from UV exposure (known to increase the risk of cataracts).
Stanford’s Marmor said doctors don’t know whether getting the antioxidants in pill form might help, what dose might be useful or whether "you have to start them when you’re 20 or when you’re 60."
Supplement makers, however, say lutein supplements could reduce the risk of developing age-related macular degeneration. Craig Maltby, a spokesman for Kemin Foods in Des Moines, Iowa, which makes the FloraGLO Lutein used in the majority of lutein-containing supplements, cited an unpublished yearlong study of 90 macular degeneration patients in which visual sharpness improved among those taking lutein.
Scientists say they have little evidence that bilberry, grape seed extract or other supplements marketed to improve vision actually do so.
No one tracks the sales of most supplements designed for the eyes. But overall sales of popular antioxidants, including vitamins C, E, beta carotene, zinc and some others, grew 1.3 percent in 2002, Nutrition Business Journal in San Diego reported.
Sales of supplements containing lutein grew from $30 million in 1999 to $100 million in 2002, the journal said, with supplement and vitamin makers adding it and zeaxanthin to an increasing array of products.
Many experts recommend 500 milligrams of vitamin C, 400 international units of vitamin E, 15 milligrams of beta carotene and 80 milligrams of zinc for patients at risk of advanced macular degeneration — those who have it in one eye or who have large deposits of waste products, called drusen, that build up under the retina.
With lutein and zeaxanthin, many doctors leave dosages up to the patients.
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