Recent research has revealed that age-related macular degeneration (AMD) is twice as common in elderly smokers as nonsmokers. However it was also found that those among the elderly who ate fish at least twice weekly are almost half as likely to have AMD than those who eat fish less than once a week.
The study was conducted by Johanna Seddon, MD, and colleagues who work at the Massachusetts Eye and Ear Infirmary, which is affiliated with Harvard Medical School in Boston. The results of the study have been published in the July's Archives of Ophthalmology.
Other experts in Australia, have also found that age-related macular problems are rarer in people whose diets are rich in omega-3 fatty acid found in fish, including mackerel and salmon, as well as flax seeds and walnuts.
Seddon's study used data from 681 individual male twins in their mid-70s of which 222 of them had intermediate or late-stage AMD and 459 had early or no AMD.
These men were made to complete questionnaires regarding their smoking history, alcohol use, diets, physical activity and use of supplements and multivitamins.
According to the researchers, "Current smokers had a 1.9-fold increased risk of AMD while past smokers had about a 1.7-fold increased risk" of AMD. In addition it was found that men with the highest fish consumption of at least two weekly servings were 45 percent less likely to have AMD than those with the lowest fish consumption of less than one weekly serving.
The Australian study reported a similar pattern in participants who reported eating fish at least three times weekly.
According to Seddon and his colleagues to reduce AMD risk, striking the right fatty acid balance is important. Reduced AMD risk was seen in people who consumed high levels of omega-3 fatty acids and low levels of an omega-6 fatty acid. Omega-6 fatty acid linoleic acid, is found in vegetable oils including corn, sunflower and safflower oils.
Seddon's team writes, "The ideal omega-6/omega-3 ratio is 3:1 to 4:1. However, the average American's diet has an omega-6/omega-3 ratio that ranges from 10:1 to 50:1. Our results suggest that when our diet is rich in these omega-6 fatty acids the protective effect of omega-3 fatty acids is dampened."
Although both studies were purely observational, researchers note that the results could probably be attributed to inflammation. As they pointed out smoking boosts inflammation, while omega-3 fats reduced inflammation.