New research suggests omega-3 fatty acids can help prevent retinopathy, an eye disease that can lead to blindness in premature babies and people with diabetes.
Retinopathy causes abnormal blood vessels to grow in the retina, the light-sensitive tissue lining the inner surface of the eye. This growth can cause the retina to detach from the back of the eye, leading to vision loss.
"For people who have had diabetes for 25 years, more than half of them will have retinopathy," says Dr Lois Smith, a professor of ophthalmology at the Harvard Medical School .
"It's a very common disease that's getting even more common because it increases with obesity."
Previous studies had shown that eye diseases, such as retinopathy, are slowed down in people who eat a lot of fish.
In their study, which appears in the journal Science Translational Medicine, Smith and her colleagues looked for the specific metabolic process that produced this protective mechanism.
Enzyme key to effect
They fed mice a diet high in omega-3 fatty acids and found it prevented abnormal blood vessel growth in the retina. They found an enzyme called 5-lipoxygenase, or 5-LOX, converted omega-3 into an acid called 4-HDHA, which slowed abnormal blood vessel growth.
"We found that it was produced by a specific pathway where we eat this essential fatty acid, and then it's made into a sub-product (4-HDHA) that specifically prevents disease formation," she says.
The researchers also found the benefits of omega-3 aren't affected by drugs such as aspirin or other painkillers.
"This is important for people with diabetes, who often take aspirin to prevent heart disease," she says.
The researchers say the findings provide new information on how omega-3s work, making them an even more promising option to other drugs currently used to treat retinopathy.
"We found that it had as big an effect as the current drugs that are used in these diseases, so this is huge in terms of increasing medical costs that are occurring in all countries," says Smith.
"Even more important is with the simple intervention just decreasing the disease burden and the horror of blindness in many patients is very exciting.
Smith is currently working alongside the US National Eye Institute, which is conducting a trial of omega-3 supplements in patients with advanced macular degeneration, expected to conclude in 2013.
"The only way we'll know for sure is by doing the clinical studies," she says.
"For many patients that have milder disease there is the possibility that this could prevent the progression and they would never go onto the severe disease-causing blindness."