Researchers tracked the diet and health outcomes of more than 43,000 male participants for 12 years. Using detailed food frequency questionnaires, participants were asked how often they ate fish, ranging from never or less than once per month to six or more times per week. The men in the study were also asked about four different fish items: canned tuna fish, dark meat fish such as mackerel, salmon sardines, bluefish and swordfish; other fish and shrimp, lobster, or scallops served as a main dish. The researchers assessed the effect of long-chain omega-3 polyunsaturated fatty acid, a constituent of fish believed to have healthful effects, on the risk of ischemic stroke (blood flow to a certain area of the brain is interrupted). They found that men who ate even a small amount of fish, one to three times per month from any of the fish categories, reduced their risk of ischemic stroke by 40 percent. There was no evidence of further risk reduction of stroke by consuming fish more often. The findings appeared in the Dec. 25, 2002, issue of the Journal of the American Medical Association.