First and foremost, it’s important to rule out any medical drivers or food allergies that could be causing a dislike of particular flavors or food groups. Children may avoid particular foods because they upset their stomachs. However, they may not be able to describe or identify this connection. Consult your pediatrician to investigate possible allergies or complicating medical conditions before starting any new food regime.
http://www.autismspeaks.org/blog/2012/11/09/encouraging-picky-eaters-autism-try-new-foods