That's an important point.

Decades ago, I thought I was lactose intolerant. I carried activated charcoal capsules with me wherever I went, and at the first sign of lower intestinal rumbling, swallow a couple to avert projectile diarrhea.

After trying a few different diets, I tried keto (we called it Atkins induction back then). I cut out almost all wheat due to the carb content, and lo and behold, I could eat all the cheese and cream I wanted without the slightest intestinal discomfort.

Now I put real cream in my coffee and tea, and eat cheese almost every day. I still have the half used bottle of activated charcoal caps.

What I thought was a lactose intolerance, turned out to be a wheat intolerance, that only showed symptoms when I ate dairy.

So obviously, without an elimination diet, it's difficult to know what food(s) you are intolerant of. That fiber intolerance, might be something else in disguise. I can't say.

Again, we are all different.

I was in my 40s when I went keto. I'm 78 now, with zero prescription medications. I found out what foods were troubling me. I hope you all get that lucky.