User blog comment:FairyRaven/Fairy Tail Chapter 363: The Stories That Demons Read, Review and Commentary/@comment-1153699-20131207173113/@comment-24066070-20131212054910

I remember Natsu being able to eat Etherion due to fire being one of the elements in it. He just took in the others as well, which renderend him sick. As far as I remember he couldn't eat anything that didn't contain fire.