At my old gym, there was a nutrition poster which listed how much moderation you should observe for many different kinds of foods. I remember what it said for tuna packed in water - no moderation necessary at all. Meaning it was so "non-harmful" that you could eat 2 cans a day for the rest of your life and have no predictable bad consequences. I was trying to think of other foods like this. many vegetables, of course (but interestingly, not all) mustard vinegar? Pickles?