Both Crohn's and Rheumatoid diseases are auto immune diseases. Most doctors only discuss expensive therapy, drug and surgery options. There is substantial research of reversing RA with diet.
Nutrition Interventions in Rheumatoid Arthritis: The Potential Use of Plant-Based Diets. A Review
But less so on Crohn's but enough to be promising.
from American Gastroenterological Association (AGA)
DEFINE_ME
and from Kings College in London
What is the best diet for Crohn’s disease? - YouTube