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Keep your eyes on those leafy greens

January 21, 2008|Karen Ravn | Special to The Times

Dismiss it as boring if you'd like, but "rabbit food" could be just what the doctor orders at your next ophthalmologist's visit.

Eating the right vegetables, it now appears, may help to ward off some life-changing diseases such as cataracts and age-related macular degeneration, conditions you might otherwise come eye to eye with as you get older.

Surprisingly, despite their reputation, carrots are probably not near the top of the list. Certainly, the vitamin A they're full of is necessary for eye health, says Dr. Michael Marmor, an ophthalmology professor at Stanford University School of Medicine. "But people are generally not vitamin A deficient in our society, and a high dose doesn't do any more good."

The most useful vegetables, according to new research, seem to be the leafy green ones -- such as spinach, kale and collard greens -- which are rich in the antioxidant carotenoids lutein and zeaxanthin.

These are also the only carotenoids found in measurable amounts in the eye, says Bill Christen, a professor of medicine at Brigham and Women's Hospital in Boston and Harvard Medical School. "That adds credence to the idea that they could be of benefit," he says.

Christen is lead author of a new study published this month showing that people who eat diets high in lutein and zeaxanthin are less likely to develop cataracts than others whose diets included less of those nutrients. A second new study by Australian scientists that is to be published next month, found similar results for age-related macular degeneration.

But while these studies show a diet-eye health relationship, they do not directly demonstrate cause and effect. Only one study to date has shown specific nutrients can cause reductions in risk for eye disease.

In that 2001 study, a high-dose combination of zinc and several antioxidants (not including lutein and zeaxanthin) lowered the risk of advanced macular degeneration and the vision loss that goes along with it.

Supplements based on that formula are now on the market. Designed for people who already have macular degeneration and are at high risk for having the disease progress to an advanced stage, these products contain zinc and antioxidants in amounts far exceeding their recommended dietary allowances. "They should be taken only on the recommendation of an ophthalmologist," Marmor says.

But many experts recommend that people whose eyes are healthy should take supplements with ingredients that stick closer to recommended amounts such as a multivitamin that also contains lutein, zeaxanthin and zinc.

"It makes perfectly good sense to be taking a prudent amount of nutrient supplements, along with eating a healthy diet, in order not to have problems when you're older," says Dr. Roger Steinert, professor and vice chair of ophthalmology at UC Irvine.

"There's no downside, and there's good evidence it can help," says alternative health guru and author Dr. Andrew Weil, founder and director of the Program in Integrative Medicine at the University of Arizona's Health Sciences Center in Tucson. "I would recommend that people start from an early age . . . certainly in their teens."

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A look at vision loss

Cataracts cloud the eye's lens and interfere with vision by blocking light from reaching the retina. "The lens is a bag of proteins," Steinert says. "Cataracts develop when the proteins become disorganized," similar to what happens when you fry an egg and the clear part becomes opaque white. Cataracts can be treated with surgery to replace affected lenses. The procedure is highly successful.

Age-related macular degeneration affects the retina. In advanced stages, it destroys sharp, straight-ahead vision, leaving people unable to read, drive or even recognize a friend's face. In one form known as "dry" macular degeneration, vision loss sometimes occurs because light-sensitive cells break down in the macula, a yellow spot near the center of the retina.

Alternatively, in the much less common "wet" form, leaky blood vessels grow under the retina where they don't belong. In either case, little can be done to repair the disease's damage over the long term.

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Similar traits, therapy

Different as they are, cataracts and macular degeneration share similarities. Both are age-related, have genetic components and are thought to result, in part, from oxidative damage caused by light.

Lutein and zeaxanthin might help prevent both.

In one new study, published in this month's issue of Archives of Ophthalmology, Christen of Brigham and Women's hospital led a team that analyzed the diets of more than 35,000 female health professionals who in 1993 had enrolled in an earlier research program, the Women's Health Study, and were then tracked for an average of 10 years.

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