1 · Fibre reaches the colon — the microbes' raw material
Your own digestive enzymes cannot digest dietary fibre, so it passes largely intact through the small intestine to the colon, where it becomes raw material for the gut microbiome.Gut-brain dialogue has a chemical route, and it starts with the dietary fibre you eat.Fibre's defining feature: your own digestive enzymes can't digest it, so it passes largely intact through the small intestine all the way to the large intestine (colon). And that's exactly where the gut microbiome lives.
In other words, fibre isn't 'useless residue' but the raw material fed to the gut microbiome. What fibre you eat determines what can be produced downstream. This scene draws fibre arriving in the colon as the microbes 'smell dinner' and get to work, about to ferment it into short-chain fatty acids.