Eat lots of fish like tuna! It contains omega-3 fatty acids, will reduce cholesterol, increase brain activity and make you a better person!
Avoid fish like tuna! It has high concentrations of mercury, will stunt brain activity and kill you.
Which is the truth? Both? Neither? I really have no idea.
Recent stories in media like the Wall Street Journal have talked extensively about this. A story about two weeks ago talked about a kid who ate tuna every day, and was damaged as a result. In addition, there is a commentary in today's Journal talking about this concern as a myth. (registration required).
I really like tuna. I have two small kids, and they also really like tuna. I have no idea what the truth is here. I don't think anybody else knows either.