chronic systemic health problems require improvements in the mental , spiritual and physical for total health! cutting out processed/junk foods and foods you notice you have an allergy/response to is a great idea but there is no 'one diet' that is suitable for every person suffering digestive ailment , diet should be a case by case basis.
for me i found changing the physical (putting healthier foods into my mouth , more exercise , moreless alkaline baths , good supplements etc) has improved both my mental and spiritual and started me on my way to complete healing.