Fish is an ideal lean protein source, low in saturated fat. Certain varieties such as salmon are also high in omega-3 fatty acids—vital for heart and possibly brain health. Unfortunately, some species also contain contaminants: If possible, eat wild versus farm-raised salmon and limit albacore (white) tuna to one meal a week. If you're pregnant or nursing, check out the guidelines at epa.gov/ost/fishadvice/advice.html.