What happens in the large intestine?

Bacteria in the large intestine break down fiber, producing gas and other chemicals. Muscles in the colon remove excess water from intestinal contents.

When waste first enters the large intestine, it contains large amounts of food that cannot be digested in the small intestine, like fiber and other forms of carbohydrate. Bacteria in the large intestine then break down these materials, and in the process the bacteria produce large amounts of chemicals and gas. This gas production often causes cramping, bloating, and flatulence. The colon also squeezes excess water from fecal matter, to avoid undue water loss.