Start with simple steps by repopulating your gut flora with super drinks like
kefir and beet kvas, eat fermented vegetables
daily, liberally consume bone broths (properly prepared — see Nourishing Traditions book by Sally Fallon and Mary Enig), eat
grains that are only properly prepared (soaked for at least 12 hours in salty and slightly acidic water), make sure your diet consists of foods rich in vit.