I suspect this happened to my husband and I about 10 years ago when we tried one of those prepackaged diets with all fake sugar. It destroyed our digestive systems, plus he got a lot of new onset allergies and I got IBS. He finally recovered going on Keto four years ago. We both tried probiotics but they made us both so sick (except I could tolerate water Kefir)
Anyway, I was able to keep on an even keel with IBS with a low carb and low FODMAP diet until a few months ago. I believe I am finally healed of IBS and I think it had something to do with the protocol I took during Covid. I also can digest red meat now when it before caused me digestive distress and a rash.
I believe it - I don’t really do the “keto” thing, but 24 hour fasting daily regularly, 48 hour fast once in a while, and it gives the “gut” time to repair and regroup for lack of a better term among other things, and rest for the digestive system. I drink a live yeast Hefe Weissen now and then to keep my gut flora healthy. Yep, that’s my story and I’m stickin’ with it.