Tuna doesn't have adequate amounts of vitamin E and this may lead to a condition called steatitis (also known as yellow fat disease). (catbehaviorassociates.com)
Even tuna that is meant for humans should not be fed to cats, tuna is high in polyunsaturated fat and cats that are fed too much tuna could develop yellow fat disease. (best-cat-art.com)
However, tuna does not contain enough vitamin E and can cause yellow fat disease, or Hepatic Lipidosis, which damages the liver. (animalbehaviorcollege.com)