For a lot of people, when they think about digestion they think of the stomach but your digestive system is much larger and more complicated than that. In 370 BC, Hippocrates, who famously quoted ‘all disease begins in the gut’, died at the age of 90 which really does make you think that he might have been on to something. When you consider how many functions your digestive system performs, it makes sense that it is the foundation of our health.
What is your digestive system?
Your digestive system can be considered in two parts, a collection of hollow organs (mouth, oesophagus, stomach, intestines, colon and appendix), and solid organs (liver, pancreas, gall bladder) which acts as a disassembly line to break down food and absorb its nutrients. However, as we’ll discuss later, it does many things beyond digestion.
What do the different organs do?
The mouth is where digestion starts, food is physically broken down when you chew and saliva starts a chemical breakdown as well.
The oesophagus is a long, muscular tube connecting your mouth to your stomach. When you swallow, the muscles squeeze together, moving food downwards. It also has two muscular rings (sphincters), the upper one primarily works to prevent food, liquids etc. from entering the windpipe and the lower prevents stomach acid from rising up into the oesophagus.
The stomach contains hydrochloric acid and enzymes that start the digestive process of breaking down food. As well as these chemical reactions, muscles in the stomach churn food to break it down into a liquid.
The small intestine is divided into three parts; the duodenum, jejunum and ileum which all perform different roles. The duodenum is the shortest section of the small intestine and is where most chemical digestion happens using bile and enzymes (substances that help us digest food by breaking them into smaller parts). The middle portion (jejunum) has an abundance of villi, which are small finger like projections extending out from the inner wall of the small intestine. They produce certain enzymes and are the main sight for nutrients to be absorbed. The ileum also has villi and the remains of nutrient absorption happens here.
The large intestine, commonly known as the colon is also divided into sections and includes the appendix. The colon absorbs water and electrolytes. Bacteria here produce vitamin K (important for bone health and blood clotting) and biotin (used to metabolise fats and carbohydrates, as well as being important for the nervous system). The appendix is primarily believed to have lost most of its original function through evolution, as it is larger and more utilised in plant eating animals. However, there are some suggestions that it may support and protect beneficial bacteria by acting as storage or may act as lymphatic organ and play role in immune system.
The pancreas secretes hormones including insulin and glucagon, as well as digestive enzymes to break down carbs, proteins and fats.
The gallbladder stores bile, a liquid made by your liver, which helps digest fats and certain vitamins.
The liver produces hormones, stores glycogen (which is used for energy), breaks down red blood cells so we can replace them with new, healthy ones, synthesises proteins and detoxifies (removes potentially harmful substances).
So what does it all mean and why is a happy digestive system important?
The most obvious benefit of a happy and well functioning digestive system is being able to obtain nutrients from your food. Even with the best diet in the world, if your digestion is compromised in anyway, it can be difficult to breakdown and absorbs carbohydrates, fats, proteins, vitamins and minerals. Sufficient nutrition underpins every process in your body so this is something we really want to get right. Most people identify they have a digestive problem when they start experiencing symptoms such as pain and bloating, these in themselves can really affect quality of life and a persons confidence so have a big impact.
Other than providing nutrients, which are the building blocks of everything else, your digestive system has many other roles which I tend to look at in four categories; hormones, immune system, nervous system and detoxification.
The pancreas and liver secrete hormones. The pancreas secretes insulin and glucagon, which work together to control blood sugar levels by either telling you to absorb sugar from your blood stream to use for energy (insulin) or by telling your liver to release sugar that is stored there (glucagon) so that you have enough in your blood to use. Hormones produced by the liver have a variety of roles from blood sugar regulation, maintain blood pressure and stimulating growth to name a few.
The digestive system houses two thirds of your immune system. As well as producing components of the immune system such as white blood cells that fight infections, a healthy gut with balanced bacteria can produce anti-inflammatory compounds, antioxidants and vitamins to protect and nurture the body. (Conversely, harmful bacteria or imbalances can produce toxins, mutate DNA and affect the nervous and immune system).
The digestive system is primarily controlled by the enteric nervous system, a complex network that runs throughout the system and is often referred to as the ‘second brain’. It comes as no surprise then to learn that the digestive system produces the majority of neurotransmitters (a chemical that sends messages) in the body. Without neurotransmitters, most communication throughout the body isn’t possible.
Although ‘detoxing’ is a very popular term in the media and brings to mind diets and cleansing teas, your liver detoxes your body all day, every day. Your liver processes many chemicals such as environmental toxins or natural hormones you produce to remove them from your body. A sluggish digestive system can lead to a build up of these substances, which can lead to a variety of symptoms and problems.