For years, doctors have been begging patients to skip the sirloin and order the salmon now and then. Yet Americans still consume seven times as much red meat as fish. Only about one in five eats the recommended two servings of seafood per week. © 2009 Jupiterimages CorporationThe biggest reason medical researchers love fish: It combats the top health threat in the United States. Why don't we take the plunge more often? We're confused -- and a little uneasy -- about fish. By now, you've heard tha