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High levels of antioxidants and zinc significantly reduce the risk of
advanced age-related macular degeneration (AMD) and its associated vision loss.
These same nutrients had no significant effect on the development or
progression of cataract. These findings from a nationwide clinical trial are
reported in the October 2001 issue of
Archives of Ophthalmology.
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,
which are 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
and/or number increases a person's risk of developing advanced AMD, which can
cause serious vision loss.
The three stages of AMD analyzed in this study are:
These two forms of advanced AMD can cause serious vision loss. Scientists
are unsure about how or why an increase in the size and/or number of drusen can sometimes lead to advanced AMD, which affects
the sharp, central vision required for the 'straight ahead' activities in our
daily routine, such as reading, driving, and recognizing faces of friends. One
observation is that the larger and more numerous the drusen,
the higher the risk of developing either form of advanced AMD. People who have
advanced AMD in one eye are at especially high risk of developing advanced AMD
in the other eye. The formulation used in the study contained several
antioxidant vitamins, which are nutrients that can help maintain healthy cells
and tissues. They also contained zinc, which is an important mineral
incorporated into many body tissues.
The nutrients evaluated by the AREDS researchers contained 500 milligrams of
vitamin C; 400 international units of vitamin E; 15 milligrams of
beta-carotene; 80 milligrams of zinc as zinc oxide; and two milligrams of
copper as cupric oxide (Copper was added to the AREDS formulations containing
zinc to prevent copper deficiency, which may be associated with high levels of
zinc supplementation). In this trial, the NEI collaborated with Bausch & Lomb, an eye care company that provided the formulation
evaluated by the AREDS researchers and financially supported the laboratory
testing and distribution of study medications.
"Previous studies have suggested that people who have diets rich in
green, leafy vegetables have a lower risk of developing AMD," said
Frederick Ferris, MD, 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 AREDS 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."
The Age-Related Eye Disease Study involved 4,757 participants, 55-80 years
of age, in 11 clinical centers nationwide. Participants in the study were given
one of four treatments: 1) zinc alone; 2) antioxidants alone; 3) a combination
of antioxidants and zinc; or 4) a placebo, a harmless substance that has no
medical effect. The benefits of the nutrients were seen only in people who
began the study at high risk for developing advanced AMD -- those with
intermediate AMD, and those with advanced AMD in one eye only. In this group,
those taking "antioxidants plus zinc" had the lowest risk of
developing advanced stages of AMD and its accompanying visual loss. Those in
the "zinc alone" or "antioxidant alone" groups also reduced
their risk of developing advanced AMD, but at more moderate rates compared to
the "antioxidants plus zinc" group. Those in the placebo group had
the highest risk of developing advanced AMD.
Dr. Ferris said some people with intermediate AMD may not wish to take large
doses of antioxidant vitamins or zinc because of 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."
In the cataract portion of the study, researchers discovered that the same
nutrients had no significant effect on the development or progression of
age-related cataract. A cataract is a clouding of the eye's lens that blocks
some light from reaching the retina and interferes with vision.
"Participants taking the 'zinc alone' treatment, the 'antioxidants alone'
treatment, or the combination of zinc and antioxidants were all about as likely
to develop a cataract as those taking a placebo," Dr. Ferris said.
"At the time the study was planned, laboratory and animal research had
suggested that antioxidants might be of benefit in treating or preventing
cataract," he said. "Also at that time, limited epidemiologic and
clinical trial data suggested that antioxidants might affect the development of
cataract. However, our analyses did not find any connection between the
antioxidant vitamins used in the AREDS and cataract development."
Despite the evidence that these nutrients did not lower the risk of cataract
development over the seven-year period of the study, Dr. Ferris noted that an
effect over a longer period of time, or with different doses of these or other
antioxidants, cannot be ruled out.
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," he said. "Slowing the
progression of AMD to its advanced stage will save the vision of many who would
otherwise have had serious vision impairment."
A list of studies centers
is available.
The National Eye Institute (NEI) is part of the National Institutes of
Health (NIH) and is the Federal government's lead agency for vision research.
NEI-supported research leads to sight-saving treatments and plays a key role in
reducing visual impairment and blindness. The NIH is an agency of the