Butyrate
Your colon cells run on a molecule made by bacteria eating your leftovers.
Grounded in the research on butyric acid
What it actually is
Butyrate is a four-carbon short-chain fatty acid. Your colon cells — colonocytes — use it as their primary fuel, pulling roughly 70% of their energy directly from it. It's not some supplement-store invention. It's a metabolic byproduct your gut bacteria produce when they ferment dietary fiber you couldn't digest yourself. The cell eats the waste product of the bacteria. That's the deal.
Where the science started
The fermentation angle was nailed down across several labs in the 1980s. Marcel Roberfroid and others mapped how anaerobic bacteria — Faecalibacterium prausnitzii, Roseburia, Butyrivibrio — break down resistant starch and non-digestible oligosaccharides into acetate, propionate, and butyrate. Butyrate gets absorbed almost entirely at the colonic mucosa. Almost none of it makes it into systemic circulation under normal conditions. It lives and dies in the gut.