Two new studies give one more reason to eat a diet
rich in fish: prevention of age-related macular degeneration,
the leading cause of blindness in old age.
The omega-3 fatty acids found in fish such as salmon
are already known to help the heart and brain stay
healthy. The new studies, appearing Monday in the
Archives of Ophthalmology, add to evidence that fish
eaters also protect the eyes.
The new studies aren't the strongest level of scientific
evidence, but they confirm the findings of previous
studies that also link fish consumption with prevention
of macular degeneration.
A study of 681 elderly American men showed that those
who ate fish twice a week had a 36 percent lower risk
of macular degeneration. In the other study, which
followed 2,335 Australian men and women over five
years, people who ate fish just once a week reduced
their risk by 40 percent.
The U.S. study also found that smokers nearly doubled
their risk of the eye condition compared to people
who never smoked.
Macular degeneration starts with blurring in the
center of what the eye sees. It progresses to blindness,
slowly or quickly depending on the type of disease.
Six to 8 percent of people age 75 and older have an
advanced form of the disease.
"We have a longer life expectancy so the prevalence
and burden related to age-related macular degeneration
will continue to increase," said Dr. Johanna Seddon
of the Massachusetts Eye and Ear Infirmary in Boston,
lead author of the U.S. study.
The proper balance of essential fatty acids was crucial
to preventing eye disease in the study, Seddon said.
The men who ate not only more omega-3 fatty acids,
but also fewer omega-6 fatty acids, found in vegetable
oils and baked goods, got the most benefit.
Both studies on the effect of fish were based on
participants' recall of what they ate. The studies
were observational, meaning they observed people's
behavior and health. Although the researchers tried
to account for other risk factors, the people who
ate more fish may have had other healthy habits that
lowered their risk.
Stronger evidence may come in five or six years with
results from a large, randomized study of how fish
oil and another nutrient, lutein, affect macular degeneration,
said Dr. Emily Chew of the National Eye Institute,
who is heading that study.
Volunteers will be assigned randomly to get either
fish oil, lutein, or both — or placebos.
Researchers don't yet know why eating fish seems
to protect the eyes. Omega-3 fatty acids may neutralize
free radicals in the eye, preventing the formation
of new blood vessels, reducing inflammation or all
three, Chew said.
Dr. Yu Guang He of the University of Texas Southwestern
Medical Center said the new studies confirm findings
from other research and will give doctors even more
confidence as they advise patients what they can eat
to protect their eyesight.
"I always tell them if you like fish, if you enjoy
fish, eat more fish. Some people don't like the flavor.
I would encourage those people to take (fish oil)
supplements," he said.
