Cataracts—an opaque buildup of damaged proteins in the lens of the eye—are
the leading cause of visual decline in those over 65. In fact, most people in
that age group have at least the beginnings of cataract formation. Many factors
contribute to the development of cataracts but damage by free radicals is
believed to play a major role. (See the article on atherosclerosis for a
description of free radicals.)
Cataracts can be removed surgically. Although this has become a relatively
quick, safe, easy, and painless surgery, it does not result in completely normal
vision. Clearly, preventing cataracts, if possible, would be preferable.
Treatment
Principal Proposed Treatments for Cataracts (Prevention):
Antioxidants
Numerous observational studies suggest that high intake of antioxidants such as
vitamin C, vitamin E, and carotenoids (beta-carotene, lutein, and lycopene) are
associated with a reduced incidence of cataracts.
However, the results of observational studies are notoriously unreliable. It is
quite possible that individuals who consume a diet rich in antioxidant vitamins
have other lifestyle habits that could be responsible for the benefits seen.
Furthermore, foods containing antioxidants also contain numerous other active
substances, which could be responsible for the effects seen in some studies
rather than the identified antioxidants themselves.
Studies that involve actually taking supplements (intervention trials) can
provide much stronger evidence regarding whether a treatment actually works.
Unfortunately, the results of a recent large intervention trial were not
encouraging.
This double-blind placebo-controlled trial studied the effects of antioxidant
supplements in 4,629 older individuals. Participants received either placebo or
an antioxidant supplement containing 500 mg of vitamin C, 400 IU of vitamin E,
and 15 mg of beta-carotene. The results over more than 6 years showed no effect
on the risk of development of cataracts nor the rate at which existing cataracts
grew worse.
A previous double-blind placebo-controlled study examined the use of
beta-carotene or vitamin E alone and failed to find them effective.
Other Proposed Treatments for Cataracts (Prevention):
Herbs high in antioxidant flavonoids are frequently suggested for preventing
cataracts. These include bilberry, ginkgo, OPCs, and turmeric. For various
theoretical reasons, the supplements cysteine, lipoic acid, niacin (vitamin B3),
riboflavin (vitamin B2), selenium, taurine, and zinc have also been proposed.
However, there is little real evidence that any of these treatments actually
help.