I wanted to follow up on this post that I had made a couple months ago. MB did not end up curing the IBS, but niacinamide did. It seemed that the most powerful substances in improving my symptoms were those that had direct effects on the cortisol enzymes (aspirin, niacinamide, DHEA). A couple weeks of about 2-3g niacinamide and all my symptoms were gone. It's hard to say for sure that it was the niacinamide since I was also taking thyroid and amitryptyline, but these had not cured the IBS in past attempts.
I should also note that I think there are various causes of IBS. Some people may have IBS related to SIBO, in which case antibiotics may be more effective. I also think that serotonin is a likely culprit in many cases as well. I'm not sure how often cortisol is explored as the cause of IBS, but I wouldn't be surprised if it was related to many cases as well.
Great, thanks for sharing! Have you see the recent study I posted about IBS / colon aging being due to low NAD and high serotonin? Niacinamide seemed to reverse that issue, and lowering serotonin synthesis was one of the mechanisms of action.