Kittens and cats can occasionally eat tuna, but WebMD warns that too much tuna in a kitten's diet can lead to malnutrition. While kittens usually enjoy tuna, it lacks the full range of nutrients necessary for a healthy diet.
A Huffington Post article recommends limiting treats, such as tuna, to 10 percent of a cat's daily caloric intake, or about 20 calories. In addition to having a lackluster nutrient profile, tuna also contains higher than average amounts of mercury, which makes it potentially dangerous if ingested regularly. In lieu of canned tuna, kitten owners should feed their pets canned food formulated specifically for kittens. Other foods to avoid feeding kittens include bones, onions, fat trimmings and raw fish.