He might try eating only beef and water for a week or two and see if any improvement. The ultimate elimination diet. Quite a number of people over on a couple of carnivore sites have reversed various autoimmune diseases, or so they say.

https://www.youtube.com/results?search_query=Dr+shawn+baker

https://www.youtube.com/results?search_query=dr+paul+saladino+carnivore+diet+

John