User blog comment:Yxz2014/Possible big plot hole??/@comment-112.198.64.78-20140930082851

Interesting point, My only guess is... even though titans don't have actual digestive systems, They can ONLY digest titan shifters.. or that titan shifters have something inside them that gives them the ability to shift, kinda like whatever it is giving them the ability to shift latches on to the living thing absorbing it (the human dies inside the titan so the titan gets whatever is inside the human who has it)