Many studies have suggested that a diet rich in fish is good for the heart. Now there is new evidence that such a diet may ward off dementia as well. One of the largest efforts to document a connection  and the first such study undertaken in the developing world  has found that older adults in Asia and Latin America were less likely to develop dementia if they regularly consumed fish.

And the more fish they ate, the lower their risk, the report found. The findings appear in the August issue of The American Journal of Clinical Nutrition.

The study, which included 15,000 people 65 and older in China, India, Cuba, Venezuela, Mexico, Peru and the Dominican Republic, found that those who ate fish nearly every day were almost 20 percent less likely to develop dementia than those who ate fish just a few days a week. Adults who ate fish a few days a week were almost 20 percent less likely to develop dementia than those who ate no fish at all.

“There is a gradient effect, so the more fish you eat, the less likely you are to get dementia,” said Dr. Emiliano Albanese, a clinical epidemiologist at King’s College London and the senior author of the study. “Exactly the opposite is true for meat,” he added. “The more meat you eat, the more likely you are to have dementia.” Other studies have shown that red meat in particular may be bad for the brain.