Diet rich in fatty fish good for cognitive function

Dear Doctors: Our grandfather is having memory problems, and my mom is trying to get him to eat more fish. I know fish is called "brain food," but my mom says she has heard on the news that fish keeps you from getting dementia. Is this true? What about fish and mercury?

Dear Reader: Research into a link between a diet rich in fatty fish and improved cognitive function dates back decades. The findin…