Respectfully, this is a complicated subject. My bottom line is to get my fiber from real, whole foods. Green beans, brussel sprouts, kidney beans, jiciama, yams, etc. When plants are separated into each of their parts, the issues become complicated.

Historically, we dont eat the hulls of seeds of the grain family. WIth the low carb movement, this once by-product now has a job. The bran-removed to create a more stable starch ( flour) product can be very sharp like glass in its dry state because of the milling process; it does seeem to absorb a lot of water when used in recipes, and I have questions about its bulking, etc. Meaning, if well cooked in plenty of water, I dont see it being a digestion problem.

My thought is that eating a lot of any one food item deserves another look. This is not in the best interest of the GI, overall health, and such. It seems that the high fiber food products are used to replace other better quality ( high nutrition) foods like whole vegetables. In other words, those of us on LC want to have our cake and eat it too, and these fibers allow us to nibble on a sweet without a high impact on our blood sugars.

Otherwise, drinking enough water and exercise also plays a part ; and in horses we use mineral oil to prevent constipation as it is not absorbed and greases the skids. Good for pre surgery.

All very complicated,but comes down to reasonable amounts of bran and hulls as monogastrics are not designed for these fibers in high quantity.