Tuna is a great source of protein, selenium and vitamin D, regardless of whether it comes from a can or it's freshly caught. However, tuna, like a lot of other fish, can be a source of mercury. So when you're stocking your pantry with canned tuna, look for cans of smaller fish, like skipjack rather than cans of albacore, yellowfin/ahi and bigeye tuna. And yes, you can feel safe about eating canned tuna. In fact, the U.S. Food and Drug Administration (FDA) says it's just fine to eat at least two to three, 4-ounce servings of canned tuna a week. So go ahead and fill up your pantry so you have plenty on hand for your favorite classic tuna fish sandwich.