Your gut bacteria may decide what a fibre supplement does for you
The same daily dose of fibre produced different chemistry depending on whether Prevotella or Bacteroides bacteria dominated a person's gut, with arabinoxylan raising the beneficial fatty acid propionate and Bacteroides-dominated guts showing the broadest response. Inulin shuffled the bacterial mix without raising short-chain fatty acids at all, and neither fibre budged glucose or insulin in anyone.
For you: A reason not to expect any single fibre supplement to do for you what it did for someone else; the response may hinge on which bacteria dominate your gut.
What it shows: A proof-of-concept finding at best: just 23 healthy adults took each fibre for one week at a time, so nobody knows whether these gut-type differences last or translate into real health outcomes.RCT · J Nutr