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Fish Oil May Save Eyesight
Seniors whose diets are rich in omega-3 fatty acids found in oily fish
and fish oil supplements could reduce their risk of age-related macular
degeneration (AMD) by up to 70% say U.S. and Australian researchers.
Macular degeneration affects over 30 million people worldwide, and
is the leading cause of blindness in people over 50.
People who ate fish at least twice weekly were 45% less likely to
have AMD than those who ate fish less than once a week according to
Johanna Seddon, M.D. and colleagues at the Massachusetts Eye and Ear
Infirmary, affiliated with Harvard Medical School in Boston.
Experts at the University of Sydney found that people who ate three
or more portions of oily fish per week reduced the risk of age-related
macular degeneration (AMD) by 70 per cent. Those who ate at least one
portion of fish every week reduce their risk of developing early AMD
by 40 per cent.
"Insufficient essential fatty acid intake could result in abnormal
retinal metabolism and cell renewal," while higher levels of omega-3
especially from fish "may protect against retinal oxidation and
degeneration," said the report by Brian Chua, BSc, MBBS, MPH, and
other researchers on behalf of Westmead Millennium Institute and Vision
Co-operative Research Center in Sydney.
Both studies are reported in the July issue of the jourrnal Archives
of Ophthalmology. Seddon’s team in the U.S. studied data
from 681 individual male twins in their mid-70s who were World War II
veterans. The Australian five-year study analysed the dietary intakes
of 2258 people 49 and older in Sydney, Australia (average age 64).
Fatty Acid Balance
When it comes to reducing AMD risk, striking the right fatty acid balance
might be important, note Seddon and colleagues.
In their study, the reduced AMD risk was mainly seen in people who
consumed high levels of omega-3 fatty acids and low levels of an omega-6
fatty acid called linoleic acid found in most vegetable oils.
“The ideal omega-6/omega-3 ratio is 3:1 to 4:1,” Seddon’s
team writes. “However, the average American’s diet has an
omega-6/omega-3 ratio that ranges from 10:1 to 50:1." Over-eating
omega-6 fatty acids -- found in oils from corn, safflower and sunflower
-- diminishes the protective effects of omega-3s.
Limitations of the Research
The studies do not prove that eating fish prevented AMD. Both
studies were purely observational; participants weren’t asked
to change their diets. The studies also don’t specify what type
of fish participants ate, or how the fish was prepared.
Nevertheless, the results are reliable after adjusting for other AMD
risk factors. Inflammation might partly explain the results, the researchers
note, and omega-3 fats reduce inflammation.
Sources: Media reports and Seddon, J. Archives of Ophthalmology,
July 2006; Vol. 124: pp. 995-1001. Chua, B. Archives of Ophthalmology,
July 2006; Vol. 124: pp. 981-986.