Zinc, Antioxidants Stave Off Eye Disease
Combination can prevent age-related macular degeneration
FRIDAY, Oct. 12, 2001 (HealthDayNews) -- A new study has found that a simple regimen of antioxidants along with high levels of zinc significantly reduces the risk of advanced age-related macular degeneration (AMD), a leading causes of vision loss and blindness in the United States.
The results should benefit hundreds of thousands of Americans who currently have intermediate or advanced AMD in one eye.
The six-year study, conducted by the National Eye Institute and reported in the latest issue of the Archives of Ophthalmology, followed more than 3,500 people, aged 55 to 80, at 11 clinical sites around the country.
The volunteers, all with varying stages of AMD, were divided into groups according to the severity of their condition. The subjects were then randomly assigned to one of four treatment plans: 80 milligrams of zinc alone; antioxidants alone (500 milligrams of vitamin C, 400 IU of vitamin E, and 15 milligrams of beta-carotene); a combination of zinc and antioxidants, or a placebo.
Participants with intermediate or advanced AMD in only one eye who took the combination treatment lowered their risk of developing advanced stages of AMD by about 25 percent and their risk of vision loss by about 19 percent. Taken alone, zinc reduced the risk of advanced AMD by about 21 percent and the risk of vision loss by 11 percent. Antioxidants alone reduced the risk of developing advanced AMD by about 17 percent and the risk of vision loss by about 10 percent.
"It's a very big deal to take a disease like AMD, for which there's really no markedly effective treatment, and prevent the development of this disorder in 25 percent of people," says study leader Dr. Frederick Ferris, clinical director at the National Eye Institute. "We were hoping for 10 to 20 percent. To get 25 percent was remarkable."
The study did not find any relationship between the dietary supplements and the development of cataracts, another leading cause of visual impairment and blindness which can effectively be treated with surgery. A related study, reported in the same journal, found that high doses of vitamin C, vitamin E and beta carotene didn't lower the risk of age-related cataracts.
The antioxidant/zinc report "is an extremely good study, and it's reassuring to me as a practitioner because it's what I've been recommending to my patients for two years," says Dr. Anne Sumers, a spokeswoman for the American Academy of Ophthalmology and a private practitioner in Ridgewood, N.J. "We know now that this is going to help my high-risk patients."
No one is quite sure why these dietary supplements are effective, but researchers have long been interested in zinc as a possible remedy for vision loss because it is found in unusually high concentrations in cells right under the retina of the eye. A small clinical trial conducted in the mid-1980s showed a benefit from zinc and led to the marketing of a number of products. That study, however, was very small and other evidence proved inconsistent.
Based on the new study, the National Eye Institute is recommending that anyone older than 55 have dilated eye examinations to determine their risk of advanced AMD. Risk is determined by looking at the size and number of drusen, which are yellowish-white deposits under the retina. Those with extensive medium-size drusen or at least one large drusen in one eye may be at risk and may benefit from taking the dietary supplements.
Although the dietary supplement regimen is relatively simple, cheap and available over the counter, there are some caveats, so it's worth consulting your physician before starting. "This is not chicken soup, and you're taking high doses of these supplements, and there could be consequences," warns Ferris.
A few side effects were reported in the study, mainly genitourinary problems in a small number of people who took zinc (either in combination or alone); a slightly higher rate of anemia among participants taking zinc and yellowing of the skin in some participants taking beta-carotene.
Beta-carotene is not recommended for smokers because it has been shown to increase the risk of lung cancer. And high levels of zinc always should be accompanied by copper supplements to reduce the risk of copper-deficiency anemia. There's also a possibility that the zinc and the antioxidants will interact with prescription and other over-the-counter medications.
One final word of caution: Because the study participants were overwhelmingly (96 percent) white and well nourished, the benefits may not extend to the general population.
The participants will continue to be monitored for five years to assess long-term effects and possible complications, although without a placebo comparison group. The at-risk participants who were taking a placebo are now all happily taking the supplements.
In the related study on cataracts, 4,629 people took either antioxidants, antioxidants and zinc, zinc only or an inactive substance. The researchers found "no apparent effect on the seven-year risk of development or progression of age-related lens opacities or visual acuity loss."
What To Do
Some companies sell zinc-antioxidant formulations specifically for your eyes. The giant eye care company Bausch & Lomb provided the supplements for the study and will be marketing them. If you want to use products already available in stores, make sure you read the labels to match dosages with those used in the study. "We worked hard at the beginning of the study to select levels of supplement that we thought were likely to have an effect and were also likely to be fairly safe," says Ferris.
The National Eye Institute reports that 1.7 million Americans have some form of AMD and that approximately 100,000 are already blind from the disease. The condition increases markedly in people over age 65 and could pose a significant public health problem as the population ages. For more information on this disease, check the National Eye Institute
Lighthouse International has information on vision rehabilitation services, education, research and advocacy, all related to vision.