Microbiology · 5 min read
The Trillions Living Inside You
Your gut microbes help digest food, train your immune system, and may even shape mood.
Your body hosts roughly as many bacterial cells as human cells—about 38 trillion—most of them in the colon.
These microbes ferment fiber into short-chain fatty acids that nourish gut cells and help regulate inflammation. The Human Microbiome Project mapped this diversity across healthy people.
Researchers are actively studying the gut–brain axis, but many claims online outrun the evidence. Association is not causation—so far.