Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the bloodstream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. In chemical digestion, enzymes break down food into the small molecules the body can use.

Your body can’t use your lunch in the form you ate it in. That’s what digestion is for—a five stage process that breaks your food down into minute components that can be absorbed into the bloodstream, extracting the nutrients and converting the unusable stuff into waste. Everything you eat or drink goes through digestion in the mouth, stomach, small intestine, large intestine, and finally, out the rectum (yes, poop).

But you don’t do all this work alone. Your gut bacteria is critical to each of these processes, breaking down complex compounds you otherwise can’t.

A gut missing these beneficial bacteria can lead to gastrointestinal disorders (Crohn’s, inflammatory bowel diseases, colitis) and even impact systemic health (obesity, diabetes, cancer).