Cost Per Serving (3 oz.): 48-77¢ Why tuna is so good for you: Sure, salmon gets a glowing (and well-deserved) rep for being a megasource of omega-3s. But did you know that lowly canned tuna also delivers omega-3s? Plus, the 2010 Dietary Guidelines recommend cutting back on meat—eating tuna up to twice a week is one way to do that. Look for chunk light tuna, which comes from smaller tuna fish and is lower in mercury than white albacore tuna.