Regularly eating fish and shellfish provides lean protein and high amounts of omega-3 fatty acids, which reduce your risk of cardiovascular disease and diabetes. A seafood diet uses fish and shellfish for your primary protein sources -- if this is something you're interested in, try it for a week to see if it's right for you. Always consult your doctor before dramatically changing your diet. The Food and Drug Administration urges women who are or may become pregnant, young children and nursing mothers not to eat fish that are high in mercury. These varieties include shark, swordfish, mackerel and tilefish.