(ARA) – Findings from a nationwide clinical trial reported that high levels of antioxidants and zinc significantly reduce the risk of advanced age-related macular degeneration (AMD) and its associated vision loss.
Scientists found that people at high risk of developing advanced stages of AMD, a leading cause of vision loss, lowered their risk by about 25 percent when treated with a high-dose combination of vitamin C, vitamin E, beta-carotene and zinc. In the same high risk group — which includes people with intermediate AMD, or advanced AMD in one eye but not the other eye — the nutrients reduced the risk of vision loss caused by advanced AMD by about 19 percent. For those study participants who had either no AMD or early AMD, the nutrients did not provide an apparent benefit. The clinical trial — called the Age-Related Eye Disease Study (AREDS) — was sponsored by the National Eye Institute (NEI), one of the Federal government’s National Institutes of Health.
“This is an exciting discovery because, for people at high risk for developing advanced AMD, these nutrients are the first effective treatment to slow the progression of the disease,” said Paul A. Sieving, M.D., Ph.D., director of the NEI. “AMD is a leading cause of visual impairment and blindness in Americans 65 years of age and older. Currently, treatment for advanced AMD is quite limited. These nutrients will delay the progression to advanced AMD in people who are at high risk — those with intermediate AMD in one or both eyes, or those with advanced AMD in one eye already.
“The nutrients are not a cure for AMD, nor will they restore vision already lost from the disease,” Dr. Sieving said. “But they will play a key role in helping people at high risk for developing advanced AMD keep their vision.”
A common feature of AMD is the presence of drusen, yellow deposits under the retina. Often found in people over age 60, drusen can be seen by an eye care professional during an eye exam in which the pupils are dilated. Drusen by themselves do not usually cause vision loss, but an increase in their size or number increases a person’s risk of developing advanced AMD, which can cause serious vision loss.
Advanced AMD can cause serious vision loss. Scientists are unsure about how or why an increase in the size or number of drusen can sometimes lead to advanced AMD, which affects the sharp, central vision required for the “straight ahead” activities, such as reading, driving and recognizing faces of friends.
“Previous studies have suggested that people who have diets rich in green, leafy vegetables have a lower risk of developing AMD,” said Frederick Ferris, M.D., director of clinical research at the NEI and chairman of the AREDS. “However, the high levels of nutrients that were evaluated in the AREDS are very difficult to achieve from diet alone.
“Almost two-thirds of AREDS participants chose to take a daily multivitamin in addition to their assigned study treatment,” Dr. Ferris said. “The study also showed that, even with a daily multivitamin, people at high risk for developing advanced AMD can lower the risk of vision loss by adding a formulation with the same high levels of antioxidants and zinc used in the study.”
Dr. Ferris said some people with intermediate AMD may not wish to take large doses of antioxidant vitamins or zinc medical reasons. “For example, beta-carotene has been shown to increase the risk of lung cancer among smokers,” he said. “These people may want to discuss with their primary care doctor the best combination of nutrients for them. With the use of the high levels of zinc, it is important to add appropriate amounts of copper to the diet to prevent copper deficiency.”
The AREDS participants reported few side effects from the treatments. About 7.5 percent of participants assigned to the zinc treatments — compared with five percent who did not have zinc in their assigned treatment — had urinary tract problems that required hospitalization. Participants in the two groups that took zinc also reported anemia at a slightly higher rate; however, testing of all patients for this disorder showed no difference among treatment groups. Yellowing of the skin, a well-known side effect of large doses of beta-carotene, was reported slightly more often by participants taking antioxidants.
“The AREDS formula is the first demonstrated treatment for people at high risk for developing advanced AMD,” Feris said. “Slowing the progression of AMD to its advanced stage will save the vision of many who would otherwise have had serious vision impairment.”