What happens to our food when we eat it is a mystery to many. Even to scientists who study the links between food, our bodies, and health, there are many unanswered questions. Part of the Institute of Food Research’s research is to better understand how food interacts with the gut.
For IFR’s Open Day in 2012, Professor Simon Carding joined up with clinicians at the Norfolk and Norwich University Hospital and swallowed a ‘Pillcam’ – a miniature camera that follows the journey taken by food as it passes through our bodies. Now, Dr Jo Brooks from the Gastroenterology team narrates these edited highlights of the Pillcam’s journey. Watch the whole video or use the smaller videos to jump to the different sections of the digestive system and find out about the structures inside and how IFR science is working to understand these complex environments and how they impact our health.
The journey begins when food is eaten and swallowed, taking it down the oesophagus into the stomach. This is a very rapid part of the process, during which the Pillcam only had time to take one image. Chewing the food begins the process of breaking down the food structure, but it is in the stomach where this really gets going.
Textbooks usually show the stomach as just a big bag, but as the Pillcam shows this isn’t really the case. The Pillcam tumbles about as the stomach actively churns food about, mechanically breaking down food structures. The Dynamic Gastric Model, or Model Gut developed at IFR accurately recreates these forces, which shear food into smaller and smaller fragments. It also replicates the gastric acid, which is the liquid seen in the video. This acid also helps to break down food structures, but also plays a role in killing off bacteria. Even so, some bacteria have evolved ways around this, and IFR researchers are trying to find out more.
After about 2 hours food leaves the stomach, and enters the duodenum, the first part of the small bowel. The ‘smoky’ fluid you can see is the digestive fluid, which also contains enzymes. By now the mechanical churning and tumbling of the stomach and the action of the gastric acid has started to break down much of the food structure, releasing the nutrients, proteins, carbohydrates and fats.
The small bowel
The small bowel is lined with frond-like structures called villi. These greatly increase the surface area for absorbing nutrients – laid out flat the surface area would cover the same area as a football pitch. In between the villi are pits or crypts, from which all new cells lining the gut derive. IFR is studying these as they are key to renewing and maintaining the gut lining and striking balance between absorbing nutrients whilst keeping unwanted invaders, such as food poisoning bacteria, from getting into our bodies. The small bowel is essentially a 7m long tube that tucks up inside us. It needs to be this long to absorb nutrients, salts and fluids as the food passes along and gets broken down. Food is moved along by a continual wave-like motion called peristalsis. Enzymes act on the food, further breaking it down.
The Ampulla of Vater is a nodule that is the main entry point for these into the small bowel, which only happens in response to eating food, or when we anticipate eating food. This is also the entry point for bile, which is the yellowish fluid you can see. Bile is produced by the liver and helps in the breakdown and absorption of fats. Exactly how we digest and absorb fats is of interest as this affects feelings of satiety – how ‘full’ we feel. Modifying how we digest fats could be used to control appetite, and so help reduce excessive weight gain and becoming obese.
The large bowel
The Pillcam shows a tumbling motion as it passes through the large bowel. This is because it is a much wider tube than in the small bowel. There are also differences in the lining of the large bowel. It has no villi. The surface is shiny and pink and blood vessels are visible. Although it can’t be seen, the lining of the bowel is covered in a layer of mucus. The whole of our gut is covered in this layer of mucus, but in the large bowel the mucus layer is structured. It has an inner layer, which acts to prevent harmful bacteria getting across the gut barrier. It also has an outer layer that helps to provide a suitable environment for beneficial bacteria. This dual role of the mucus layer is crucial to maintaining a healthy gut and is being studied at IFR.
One role of the large bowel is to absorb water from the residual fluid, so the matter solidifies further down the bowel into stool. The large bowel is also home to trillions of bacteria – there are 10 times as many bacteria living in here than there are cells in the rest of our body. They have a variety of roles in digesting food and are a source of essential vitamins and other nutrients. They also have roles in ensuring our immune system functions efficiently and effectively, as well as helping protect us from ‘bad’ bacteria. There are thousands of different species of bacteria, and different people have different communities of bacteria. Understanding more about these bacterial communities, known as the microbiota, is a major area of research at IFR.
About the Pillcam
Wireless capsule endoscopy, or the Pillcam, is used routinely by gastroenterologists to examine the small bowel, particularly to look for bleeding or Crohn’s disease which can’t be seen using other methods. The capsule contains a tiny camera and light source and takes about 8 hours to travel through the system.
Many thanks to Dr Crawford Jamieson and Dr Jo Brooks at the Norfolk & Norwich University Hospital for their time and help in putting together this project.