Is eating fish good for your brain? That may depend on how the fish is prepared. According to a 12-year study of nearly 5,000 men and women over the age of 65, eating five or more servings each month of tuna or other baked or broiled fish decreases the risk of stroke 28%. But those protective benefits disappeared when the fish was fried. Eating at least one serving of fried fish or a fish burger each week led to a 37% increase in stroke risk, which grew with each additional serving. Frying seems to alter the ratio of good to bad fats, including trans fats, in the fish--which, scientists speculate, may encourage the formation of blood clots.