Tuna is one of the basic foods of bodybuilding small in calories, sometimes no carbs, a few vitamins, loads of protein. If I were you I would take at least 1Xyour lean body weight in lbs, bodybuilders take anywhere from 1X to 2X depending on activity and progession, with tuna watch it about the carbs having scarce amounts it can really drain your energy if eaten with nothing throughout the day. If tuna was so bad for you so many bodybuilders wouldn't be eating it as they are and you will have heard at least some report of bad side effects.