According to a study, eating oily fish at least twice a week may benefit people suffering from age-related macular degeneration (AMD).
Previous studies have already shown that omega-3 fatty acids, found in abundance in fish like mackerel and salmon, can reduce the risk of getting AMD, but now this latest work suggests that these fats also benefit patients who already have the disease.
The findings are based on almost 3,000 people taking part in a trial of vitamins and supplements, reports the BBC.
It showed that progression to both dry and wet forms of advanced AMD disease was 25 percent less likely among those eating a diet rich in omega-3 fatty acids.
The study, conducted by researchers at Tufts University, Boston, also found that people with advanced AMD who also consumed a low-GI diet, eating of foods that release their sugar more slowly, and who took supplemental antioxidant vitamins and minerals like vitamin C and zinc appeared to reduce their risk of disease progression by even more - by up to 50 percent.
Substituting five slices of wholegrain bread for white bread every day out of a total intake of 250g of carbohydrate might cut out almost 8 percent of advanced age related macular degeneration over five years, say the authors.
However, the supplements were counterproductive for those with early AMD, negating the benefits of omega-3 fats, and even appeared to increase the risk of disease progression.
Those who took all the antioxidant vitamins plus zinc, and who a high daily intake of beta carotene, found in yellow and green vegetables, were 50% percent more likely to progress to advanced disease.
The researchers believe omega-3 fatty acids offer protection against AMD by altering fat levels in the blood after a meal that can be damaging to the body.
However, they say it is not clear whether patients should also consider taking supplements as well as omega-3 because of their mixed findings.
The researchers suggest that eating two to three servings of fatty fish, such as salmon, tuna, mackerel, shellfish, and herring every week, would achieve the recommended daily intake (650mg) of omega-3, substantially cutting the risk of both early and late stage AMD.
However, they warn that too much oily fish is bad because it can contain low levels of pollutants that can build up in the body.
The findings are published in the British Journal of Ophthalmology.