If you live in a city, chances are you are exposed to air pollution every day. The good news is a new study has found an impactful way to protect our brains from external threats like pollution: eating broiled or baked fish.

According to the study, which was published in the medical journal of the American Academy of Neurology, found that eating broiled or baked fish just once or twice a week may help protect the brain from the negative impacts of air pollution, thanks to the powers of omega-3 fatty acids. Omega-3 fatty acids are a type of polyunsaturated fat that is deemed an “essential fat” because we cannot produce enough without eating it as well—and fish are a popular source for many diets.

“Fish is an excellent source of omega-3 fatty acids and easy to add to the diet,” says study author Ka He, M.D., Sc.D., of Columbia University in New York. “Omega-3 fatty acids have been shown to fight inflammation and maintain brain structure in aging brains. They have also been found to reduce brain damage caused by neurotoxins like lead and mercury.”

The new research set out to see if those benefits extended to other forms of toxins, such as the fine particulate matter found in air pollution. Using a combination of blood tests, diet questionnaires, and brain scans, researchers were able to see that women who had the highest blood omega-3 levels had greater volumes of white matter and greater volumes of the hippocampus.

The study included older women (the average age of participants was 70) who lived in areas with high levels of air pollution and did not have dementia at the start of the study. The researchers assessed the amount of fish (including broiled or baked fish, canned tuna, tuna salad, tuna casserole, and non-fried shellfish) the participants consumed.

By the end of the study, they found that specifically eating fish that has been broiled or baked is linked to brain health benefits. Frying fish, however, will not give you those benefits as frying the fish damages the fatty acids.