Looking For Supplements That Aid
by Linda Roach
Take a stroll down the vitamin
aisle at your supermarket and you'll likely find a section where the vitamin or herbal
formulas are labeled as "supporting eye health." The options are many:
antioxidants, carotenoids, ginkgo, bilberry. It's a tempting place to stop if you're
concerned with the common vision problems that accumulate with aging -- macular
degeneration, cataracts, glaucoma, diabetic retinopathy.
there's not much to back up most of those uses. Even the Bible of alternative medicines
using an evidence-based approach, Germany's Commission E report, has very little to say
about whether antioxidants or other nutrients can help prevent the eye diseases of aging.
And that's the biggest uncertainty for people who want to use supplements to preserve
Also of concern is whether a supplement that contains
a lot of one nutrient could do your eyes harm by blocking others that are also important
to eye health. This is particularly the case with carotenoids, the plant compounds like
beta-carotene and lutein that are most commonly found in eye supplements.
"There are over 600 carotenoids in the food we
eat," says Dr. Donald S. Fong, a California ophthalmologist who has done research at
the National Institutes of Health on the importance of nutrients in retinal diseases.
"So if you supplement with high doses of any single one, you block the absorption of
other carotenoids you may need. And, in addition, you might increase the risk of disease
in other parts of the body."
is referring to two studies of vitamin A and beta-carotene, published in The New
England Journal of Medicine in 1994 and 1996. Both found that smokers who took
beta-carotene actually had a higher risk of lung cancer than those who puffed away without
Fresh from that lesson, most ophthalmologists won't
recommend specific nutrition supplements to their patients as a preventive. At the most,
they say, a daily vitamin/mineral combination is adequate.
The rest of the nutrients you consume in hopes of
protecting your vision should come from "functional foods," they say. That is,
eat your grains and oils for vitamin E, selenium and zinc; fruits for vitamin C and other
vitamins; and dark green, leafy vegetables like spinach and kale for carotenoids.
Because people who have the highest blood levels of antioxidant vitamins (C and E) and
carotenoids, such as lutein and beta carotene, are less likely to develop cataracts and
age-related macular degeneration, according to long-term observational studies like the
Nurses Health Study.
research can implicate nutrition as the cause of this phenomenon -- but it can't say which
nutrients are responsible or in what amounts. Nor do such studies translate into evidence that taking supplement
pills will give your body the same protective effect that a nutrient-rich diet will.
This was a key point in the April Institute of
Medicine report that increased the national Recommended Daily Allowances for vitamins C
and E and the mineral selenium. "Insufficient evidence" exists to recommend
antioxidants as a preventive for eye and other chronic diseases, the report said. Nor is
it clear that carotenoids, commonly touted as cell-protecting antioxidants, actually
function as antioxidants when consumed. The report called for large, well-controlled
studies to settle the issues.
National Eye Institute expects results by the fall of 2001 from one such project, the
Age-Related Eye Diseases Study. The study assigned 4,700 individuals -- some with varying
degrees of eye disease already -- to four supplement groups: zinc supplements;
beta-carotene and vitamins C and E; a combination of all those nutrients; or placebo.
Researchers are checking whether any of the groups develop fewer cataracts or cases of
age-related macular degeneration, a retinal disease that is the leading cause of
unavoidable blindness in elderly Americans.
Other common eye diseases of aging are diabetic
retinopathy and glaucoma. The former involves development of uncontrolled blood vessel
growth on the retina, the flat area at the back of the eye where images fall before being
sent to the brain. In glaucoma, high fluid pressure in the eye and other unknown factors
cause deterioration of the optic nerve behind the retina, preventing good visual signals
from reaching the brain.
with any of these diseases, or who have a family history they are trying to outrun, are
the prime target for advertising and health-food store shelves touting the benefits of
various "eye vitamin" supplements.
Here is what is known about the ingredients that
occur most commonly:
Lutein and zeaxanthinin
increasingly promoted carotenoids make up the macular pigment, located in the center of
the retina where the finest vision occurs. Advocates of these nutrients suggest that
taking supplements of them will help you build a thicker pigment layer, preserving vision
as you age. A study at Boston's Schepens Eye Research Institute in 1998 showed that
elderly people with thicker macular pigment reacted to light more effectively. But most
ophthalmologists say the best way to get carotenoids is in food because the eye may
require a mix of the 600 different carotenoids found in foods.
carotenoid is a precursor to vitamin A in the eye, which is essential to the biochemical
cycle in which retinal cells adapt to the dark. Consequently, "eye vitamin"
supplements often contain it. However, since blindness from vitamin A deficiency is only a
problem in very poor countries, and the Institute of Medicine and others recommend against
taking supplements except for outright deficiencies. In addition, it is the vitamin most
often mentioned as toxic at megadoses (above 50,000 International Units daily).
derivative from the fruit of a small, alpine shrub also is showing up increasingly in eye
preparations in health-food stores. The German Commission E report supports its use only
for diarrhea or inflammation of mucous membranes. However, bilberry is used in other
European countries, especially Italy, for microcirculatory disorders -- which many eye
doctors believe is an underlying problem in some retinal diseases, glaucoma and diabetic
retinopathy. Bilberry also is thought to aid the eye's rhodopsin cycle and thus improve
night vision. In this country, it hasn't been studied either for effectiveness or for
Vitamins C and E
recent Institute of Medicine report increased the Recommended Daily Allowances of these
vitamins, which many eye vitamin preparations include as cell-protecting antioxidants. The
institute recommended 75 mg. of vitamin C daily for women and 90 mg. for men, with an
extra 35 mg. daily for smokers. The RDA for vitamin E was set at 15 mg. from food, or 22
International Units for natural-source supplements (d-alpha-tocopherol) or 33 IU of
synthetic E (dl-alpha tocopherol). For the first time, the Institute's RDA panel also set
an upper safety limit for these vitamins: 2,000 mg. daily for C, 1,500 IU for natural E
and 1,100 IU for synthetic E.
Zinc and selenium
these minerals appear in many eye vitamin preparations because of evidence that they are
essential to biochemical processes in the eye. Selenium is especially touted because it is
known to function as an antioxidant elsewhere in the body, and advocates say this means it
should help prevent damage to retinal cells from normal oxidative processes there. As with
other supplements, the scientific evidence is lacking.
glaucoma specialist Dr. Robert Ritch, a clinical professor at New York Medical College and
co-author of a standard text in glaucoma, tells his patients to take daily supplements of
the herb ginkgo biloba. He believes the herb scavenges free radicals produced by oxidation
and increases the blood supply to the optic nerve. It is this nerve connecting the eye and
brain that deteriorates in glaucoma. However, the German Commission E report refers to
gingko primarily for dementia, and no controlled studies of its effectiveness in the eye
Citing European and Chinese literature on the herb,
Dr. Ritch prescribes 120 mg. twice daily for two months, then 60 mg. twice daily
indefinitely. (The only patients who don't get this advice are those on blood-thinners
because of cardiovascular problems.)