Poo and you: how your body digests its food

As soon as your meal enters your mouth, a process of breaking down takes place, in which nutrients are extracted and waste excreted.

- By Brian Robert Boulay

Much of the food you eat is absorbed by your digestive system, which includes your stomach and your intestines. But some of what you eat makes it all the way through those twists and turns and comes out the other end as poop. How does that happen?

I'm a doctor who regularly treats children and adults with digestive problems. Some of my patients have problems absorbing nutrients from their food and others poop too often or not often enough. When they describe their symptoms, I consider the process of how our bodies make poop and which steps can go wrong.

Imagine you start your day by eating a bowl of crunchy cereal with milk. The process of digestion begins as you start to chew.

Your teeth grind up the cereal into smaller particles, making it easier to swallow and digest. Your saliva contains an enzyme, a kind of chemical, called amylase that starts breaking down the cereal on a molecular or very small level.

Full of enzymes and acid

Everything you eat contains three types of molecules that provide your body with the energy you need to live: carbohydrates, fats and proteins.

Amylase, an enzyme in saliva, begins breaking down the starches, a kind of carbohydrate, while the cereal is still in your mouth. After you swallow, the milky cereal travels down your oesophagus, a tube that carries swallowed food from your mouth to your stomach. That's where digestion really gets going.