Antioxidants associated with
reduced risk of age-related macular degeneration
Newswise — A diet with a
high intake of beta carotene, vitamins C and E, and zinc is
associated with a substantially reduced risk of age-related
macular degeneration in elderly persons, according to a
study in the December 28 issue of JAMA.
Age-related macular
degeneration (AMD) is a degenerative disorder of the macula,
the central part of the retina, and is the most common cause
of irreversible blindness in developed countries, according
to background information in the article. Late-stage AMD
results in an inability to read, recognize faces, drive, or
move freely. The prevalence of late AMD steeply increases
with age, affecting 11.5 percent of white persons older than
80 years.
In the absence of effective treatment for AMD, the
number of patients severely disabled by late-stage AMD is
expected to increase in the next 20 years by more than 50
percent to 3 million in the United States alone.
Epidemiological studies evaluating both dietary intake and
serum levels of antioxidant vitamins and AMD have provided
conflicting results. One study (called AREDS) showed that
supplements containing 5 to 13 times the recommended daily
allowance of beta carotene, vitamins C and E, and zinc given
to participants with early or single eye late AMD resulted
in a 25 percent reduction in the 5-year progression to late
AMD.
Redmer van Leeuwen, M.D.,
Ph.D., of Erasmus Medical Centre, Rotterdam, the
Netherlands, and colleagues investigated whether
antioxidants, as present in normal daily foods, play a role
in the primary prevention of AMD. Dietary intake was
assessed at baseline in the Rotterdam Study (1990-1993)
using a semiquantitative food frequency questionnaire.
Follow-up continued through 2004. The Rotterdam Study
included inhabitants aged 55 years or older from a
middle-class suburb of Rotterdam, the Netherlands. Of 5,836
persons at risk of AMD at baseline, 4,765 had reliable
dietary data and 4,170 participated in the follow-up.
Average follow-up of
participants was 8.0 years. During this period, 560 persons
(13.4 percent) were diagnosed as having new AMD, the
majority of whom had early-stage AMD. A significant inverse
association was observed for intake of vitamin E, iron, and
zinc. After adjustment, a 1-standard deviation increase in
intake was associated with a reduced risk of AMD of 8
percent for vitamin E and 9 percent for zinc. An
above-median (midpoint) intake of beta carotene, vitamins C
and E, and zinc, compared with a below-median intake of at
least 1 of these nutrients, was associated with a 35 percent
reduced risk of AMD, adjusted for all potential confounders.
In persons with a below-median intake of all 4 nutrients,
the risk of AMD was increased by 20 percent. Adding
nutritional supplement users to the highest quartile of
dietary intake did not change the results.
“This study suggests that
the risk of AMD can be modified by diet; in particular, by
dietary vitamin E and zinc. A higher intake of vitamin E can
be achieved by consumption of whole grains, vegetable oil,
eggs, and nuts. High concentrations of zinc can be found in
meat, poultry, fish, whole grains, and dairy products.
Carrots, kale, and spinach are the main suppliers of beta
carotene, while vitamin C is found in citrus fruits and
juices, green peppers, broccoli, and potatoes. Based on this
study, foods high in these nutrients appear to be more
important than nutritional supplements. Until more
definitive data are available, this information may be
useful to persons with signs of early AMD or to those with a
strong family history of AMD. Although in need of
confirmation, our observational data suggest that a high
intake of specific antioxidants from a regular diet may
delay the development of AMD,” the authors conclude.
