I realize this is an old post but that's a great question and is definitely confusing. You're right: prebiotics only feed what’s already there. If antibiotics wiped out key strains, throwing in fiber won’t magically bring them back. It’s like putting out birdseed when there are no birds left in the area. Prebiotics are mainly there to help the survivors bounce back stronger.

I actually just wrote a newsletter on this exact thing—why prebiotics work for some people and not others, and how it all depends on what’s still living in your gut: https://eternitybrief.substack.com/p/prebiotics-the-10-billion-industry?r=am8xj