Zeaxanthin May Help Battle AMD

By Dennis L. Gierhart, Ph.D.

February 17, 2003
The call to increase the amount of the antioxidant zeaxanthin in the diets of those with age-related macular degeneration (AMD), whether through food, supplements or a combination of the two, is becoming more common as scientific evidence mounts in support of zeaxanthin's ability to protect the macula from this devastating disease.

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Most recently, in November 2002, research from the Schepens Eye Research Institute and Harvard Medical School, established conclusively that zeaxanthin (zee-uh-zan'-thin) plays an essential role in protecting the retina of the eye from the damaging effects of light.

These results are particularly exciting in the search for a treatment for AMD, which currently affects an estimated 17 million people, with an additional 500,000 diagnosed each year. In fact, an estimated 25 percent of those between the ages of 65-74 have AMD, and that number climbs to estimated 33 percent of those over age 75.

Characterized by the slow but steady loss of function and ability to see in the center field of vision in one or both eyes, AMD slowly robs patients of their sight and their quality of life. As the disease progresses, they grow increasingly reliant on caregivers to meet their daily needs. Most tragic of all, there is no known cure or even generally accepted treatment for AMD.

Science is working to change that, however, starting with a closer look at zeaxanthin, which along with lutein is one of the carotenoids selectively accumulated by the retina. Scientists theorize this is because they are able to provide protection by absorbing blue light and because they are powerful antioxidants.

In the Schepens/Harvard study, published in Experimental Eye Research and Investigative Ophthalmology & Visual Science (IOVS), researchers found that quail -- whose eyes most closely mimic the human eye while aging at a much faster rate -- fed a zeaxanthin-supplemented diet had significantly less retinal damage from exposure to brighter light than did those on zeaxanthin-deprived and normal diets.

"AMD is clearly influenced by genetic and environmental factors. In fact, age and the constant exposure to environmental damage such as excessive sunlight and pollution serve to accelerate its deterioration. Zeaxanthin, however, accumulates in the macula where it absorbs harmful blue wave light and acts as a potent antioxidant preventing oxidative damage, a problem that increases with aging," said C. Kathleen Dorey, Ph.D., principal investigator on the November studies.

In April 2002, IOVS published another study in which researchers concluded that zeaxanthin supplements effectively and preferentially increased the presence in quails' retina to photo-protective levels. Finally, in 2001, Florida International University researchers published results of a study of donor eyes from AMD patients and control subjects, which found that those with the highest concentration of the carotenoids were 99.9 percent less likely to have AMD.

Zeaxanthin is a strong antioxidant with superior light-filtering properties. It is preferentially absorbed from food and settles primarily in the center of the macula, where it protects by absorbing harmful blue light from the sun's rays and by acting as an antioxidant that neutralizes free radicals.

Although found in foods such as corn, oranges, eggs and certain leafy green vegetables, it is very difficult to maintain healthy levels of zeaxanthin through diet alone. According to National Cancer Institute data, most Americans currently don't consume enough zeaxanthin-rich foods, and consumption is declining in groups at the greatest risk for AMD -- women of all ages and individuals aged 40 to 69.

Now, however, thanks to research suggesting zeaxanthin supplements may restore those levels, a new class of zeaxanthin-centered dietary supplement is available.

As a supplement, zeaxanthin has been extensively tested and found to be safe, with no known side effects or drug interactions. Further, limited human volunteer trials have shown no negative interaction with fat-soluble vitamins.

In fact, the main issue surrounding zeaxanthin supplements is effective dosage levels. Among all the supplements on the market containing zeaxanthin, whether as the primary ingredient or in combination with other antioxidants, only one -- ZeaVision -- has demonstrated a capacity to deliver sufficient levels of zeaxanthin to the eye.

Yet as close as research has come to unlocking the full potential of zeaxanthin, more work remains. Additional studies, particularly human trials, are needed to provide conclusive evidence of its potential to prevent or slow AMD, as well as the ability of dietary supplements to restore and maintain healthy levels in the eye.

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Dennis L. Gierhart, Ph.D., is chairman and CEO of St. Louis-based ZeaVision L.L.C. (www.zeavision.com), where he directs day-to-day operations and oversees scientific research and development for the Company's dietary supplement, ZeaVision. Gierhart and ZeaVision hold five patents on zeaxanthin and on methods of using zeaxanthin to prevent or treat macular degeneration, and actively support additional scientific research into zeaxanthin.