A good quality probiotic daily and indefinitely. Also if you don't have stricturing CD (blockage issues) fibre supplements daily and indefinitely, something with psyllium in it.
Also, alot of people find some success using digestive enzymes, these help break your food down so it's less work for your digestive system. You can get them in supplement form but natural ones are best if you can tolerate things like Kiwi, papya and mango (which are all natural digestive enzymes work best if eaten after large/main meals).