When I got sober and had to kickstart my gut again from being on dope for years, I swore by eating rolled oats and plain greek yogurt.
Every morning: 4 tablespoons of plain, full fat yogurt, unsweetend and none of that full of glucose shit, 2 heaping hand fulls of rolled oats, add some honey to sweeten, mix that shit up and eat it. It's like magic for the gut. The yogurt and oats really feed the beneficial bacteria in your gut, as well as providing some much needed fibre. It also fills one up for a decent amount of time, and levels out the blood sugar. After a few months of this, my shitting went back to pre-addiction levels, and I could go to the bathroom and just take normal dumps again, which was such a foreign feeling.
Yogurt and Oats! Probably 50% of what got me through early recovery.