Sorbitol, IIRC, is what prunes have a lot of, that make them so effective at loosening you up. The problem is, they give some people terrible gas as well. I’m one of them too. And I do have IBS. I’ve had the blood test. There are markers in your blood, and I had just enough of them for the diagnosis, which jibes with the diagnosis of mild IBS that my PCP made symptomatically before the blood test was available.
There are a couple of other artificial sweeteners that also have a laxative effect. IIRC, mannitol is one.