How your digestive system works

You may have heard that it all starts in the gut. Your digestive system runs from your mouth, down your oesophagus to your stomach, then through your small and large intestines. It's where the nutrients your body needs to make hormones, enzymes and new cells come in, so how well it works affects your whole body.

From the first bite
Digestion starts in your mouth. As you chew, your saliva begins breaking down carbohydrates, and your vagus nerve tells your stomach to get ready. In your stomach, acid and an enzyme called pepsin start breaking down protein. Your liver makes bile, which is stored in your gallbladder and released into your small intestine to help digest fats.

Your small intestine and pancreas
Most digestion and absorption happens in your small intestine. Its lining is covered in tiny folds called villi, which give it a much bigger surface for taking in nutrients. Your pancreas adds digestive enzymes and bicarbonate to neutralise stomach acid. It also makes insulin, which helps your cells take in sugar from your blood to use for energy, and keeps your blood sugar steady.

Your appendix and large intestine
One theory is that your appendix stores good gut bacteria, which can help repopulate your gut after an illness like gastro. Your large intestine absorbs water and electrolytes, and is home to bacteria that make some vitamins. A large part of your immune system sits around your gut, and much of your body's serotonin, a chemical that affects mood, is made there too.

The role of your liver
Your liver does far more than make bile. It stores glycogen, which it turns back into glucose for energy. It also breaks down and clears things your body needs to get rid of, such as alcohol, caffeine, some medications, chemicals and hormones like oestrogen. And it helps convert thyroid hormone T4 into its active form, T3, which affects your metabolism.

When things aren't working well
When your digestion or liver isn't working as well as it could, you might notice constipation or diarrhoea, IBS symptoms, bloating or nausea, getting sick often, tiredness, headaches, brain fog, trouble sleeping, anxiety or low mood, changes to your cycle, acne, or signs of a sluggish thyroid.

If any of this sounds familiar, a practitioner can talk it through with you and help you work out what your gut needs. If your symptoms are new, severe or getting worse, please see your GP.