What is the gut microbiome?

The bloating after dinner is not food working through you. It's your gut bacteria reacting to it.

Your gut microbiome is the collection of bacteria and other microbes living mostly in your large intestine. These microbes help break down fiber, support the gut lining, interact with the immune system, and even communicate with the brain.

Most people still call it gut flora — a term that dates back centuries and is more poetic than accurate. Scientists began using the word microbiome as sequencing technology made it possible to identify the full range of microbes in the gut. That shift accelerated with projects like the NIH Human Microbiome Project, launched in 2007, which used DNA sequencing to identify microbes that previous methods had missed.

Gut bacteria turn fiber into short-chain fatty acids like butyrate — a compound that helps feed the cells lining the colon and supports the protective lining of the gut. Foods like 🧄 garlic, onions, 🌾 oats, bananas, and beans help feed the bacteria already in your gut. That fiber gets fermented into compounds like butyrate inside the colon, which is why eating fiber is different from actually benefiting from it.