The omega-3 fatty acids in fish counter the worst effects of air pollutants, which can shrink the hippocampus and the amount of white matter in the brain, responsible for memory and problem-solving.
Researchers from Columbia University in New York studied 1,315 women with an average age of 70 and who weren't showing any signs of dementia. They measured the amount of fish they ate every week and included in the tally were steamed and baked (roast) fish and canned tuna, but excluded any fried fish as the method of cooking damages the fatty acids. They also measured the amount of air pollutants in the areas where the women lived.
The women with higher levels of omega-3 in their blood had more white matter, and the fats also protected the brain of the women living in more polluted areas, the researchers found.
The research underlines the importance of omega-3 on brain health. Earlier studies found the fats also counter inflammation and help maintain brain structure as we get older.