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Writer's pictureThe eatwell dieticians

How does digestion work?

The foods we eat have an intricate relationship with and impact on your body, brain and hormones. Your digestive system (also known as your gastrointestinal tract or gut) is the group of organs which start at the mouth and end at the large intestine and include the esophagus, stomach, pancreas, liver, and gallbladder along the way. Your gastrointestinal tract plays the most significant role in absorbing nutrients into the body and is also the primary location for your immune system. You will already be familiar with the main roles that these organs play but we will provide a quick recap on them now.





The digestive system

Digestion starts at the mouth. As you chew on your lunch, you start to break your food into smaller pieces. Saliva is secreted from glands in your mouth and helps break down the carbohydrates in your food into simple sugars. The taste buds on your tongue send messages to the brain about how the food tastes to tell you if it is sweet, sour, bitter or salty and to help you remember them for the future – we’ll take a look at how your brain interprets these flavors in a later blog.


When you swallow, your food then travels down the esophagus to the stomach where it gets to work alongside the pancreas and gallbladder. The stomach is an internal organ with an acidic environment that helps break protein down into smaller pieces with not too much more happening to fat and carbs at this point. The pancreas is a gland organ behind the stomach that has two main functions: producing enzymes to help digestion and producing hormones to regulate the body’s glucose or sugar levels. The pancreas works in conjunction with the gallbladder which is a small organ located just under the liver that stores acids critical for the digestion and absorption of fats and fat-soluble vitamins called bile.

Your stomach muscles contract periodically, churning food to enhance digestion and controlling the release of food into your small intestine while the pancreatic enzymes and bile salts help break down the components of your food even more. The protein molecules are broken down into amino acids and peptides, the fats are broken down into glycerol and fatty acids and the carbohydrates are broken down into simple sugars. The most useful nutritional components are then absorbed through the lining of your small intestine and into the bloodstream where almost everything is transported to your liver.


The liver is an amazing organ that carries out a number of really important tasks. It helps make fat out of any excess carbohydrates that can be used for energy later, it stores important substances (like vitamins A, D, B, copper and iron), it produces bile, which is then deposited into the gallbladder, it helps make important proteins to prevent blood clotting and it is critical for metabolic regulation. The liver is also responsible for blood filtration and detoxifies the compounds in your blood before they are transported to the rest of your body. If any bacteria, hormones, drugs or alcohol are absorbed through your intestinal lining and get past your immune system – we’ll cover this in the next blog – then those toxic components will be filtered out of your bloodstream by the liver before they get into the rest of the body. The remainder of your meal in your gut then passes into your large intestine which reabsorbs any final water and minerals before the leftover solid waste is excreted as feces.

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