How does the gut influence our mental and physical health?
Could the gut be the key to understanding our mental health and physical well-being? Is having a “gut feeling” more than just a figure of speech? The gut, also known as the Gastrointestinal tract (GI tract), is responsible for processing food from the moment it enters the mouth to the moment it leaves the body through digestion. To understand how the gut would have anything to do with our health, it is important to have a basic understanding of how it works. First, let’s take a look at what the gut does and how it does it.
What does the gut do?
The gut begins by breaking down food in the mouth and pushing it through the esophagus, where it ends up in your stomach so acid and enzymes can break down the food before it passes to the small intestine. In the small intestine, digestive juices and enzymes break down carbohydrates, fat and protein and absorb nutrients and water into the bloodstream where it is pumped around the body. The gut is full of bacteria that helps to produce enzymes to break down and process food, regulate our immune system, produces vitamins and protects against pathogenic bacteria; this is known as the gut microbiome. We all have our own unique gut microbiome made up of both beneficial and non-beneficial bacteria, which has been influenced and formed by a variety of factors. For example, much of a baby’s gut microbiome is formed during birth as the birth canal is chock full of bacteria which is passed on to the baby by mother. Whether or not you were breastfed as an infant can influence the microbiota composition also, as can other environmental factors like diet and climate.
Next is the large intestine which is responsible for breaking down and absorbing the remaining nutrients and water, making vitamin K and turning waste products into stool before they are passed from the body. Behind the process of digestion is a complicated telephone wire network of signals in the form of hormones and nerves from the gut to the brain, sending messages to control the process of digestion. There is a gut-brain connection and access, meaning that this part of our body is intrinsic to our immune system, metabolism and potentially our mental health. This is known as the gut-brain axis. Combined with the gut microbiome, these two key parts of human biology are extremely important to unlocking important facts about our health.
The gut-brain axis and gut microbiome
To put this in perspective, we have ten times more bacterial cells than human cells and over a hundred times more bacterial genes associated with our collective genome than human genes, so humans are more microbial than human. The gut houses the largest number of immune cells in the body which are in constant communication with the gut microbiome to maintain a balance that can impact our overall health, from respiratory infections to how well we respond to a vaccine. Things that may alter our gut microbiome and influence the gut-brain axis are diet, stress, medications and antibiotics. For example, disruption to the gut microbiome can cause dysbiosis, which is an imbalance in the types of gut bacteria, this can increase the permeability of the intestine, allowing bacteria to escape. This is known more commonly as leaky gut syndrome! A continued increase in intestinal permeability can lead to changes in the immune system that have been demonstrated in inflammatory bowel disease, depression, anxiety and autism.
When the gut becomes inflamed, the over production of cytokines (proteins used for cell signaling) increases the permeability of the blood-brain barrier, which further increases the effect of molecules escaping from the gut, further increasing depression and anxiety.
Signs you have an unhealthy or unhappy gut
Some signs and symptoms of an unhealthy or unhappy gut are:
- Upset stomach and nausea
- High sugar diet
- Skin irritation
- Food intolerances
How can we protect our gut health?
Diet and water intake are two of the main ways we can protect and improve our gut health. Dietary fibre is important for making short-chain fatty acids that are responsible for cell signaling (how cells communicate with each other and the brain to carry out different tasks) needed to regulate immune cells. Examples of dietary fibre are wholegrain pasta and rice, broccoli, beans, nuts and pulses. Making sure you get enough water is equally important. Water helps to promote a healthy gut by maintaining the mucosal layer of the intestine to reduce the likelihood of intestinal permeability.
Fermented foods are a great natural source of probiotics. A probiotic is a live organism that can help to restore and maintain gut flora. Examples of fermented foods are yogurt, tempeh, miso and kefir.
Food intolerances can also contribute to an unhealthy gut, so it is important to check for food intolerances and do an elimination diet to see if it improves your symptoms. If you suspect you have a food allergy you must make sure this is tested and seek the advice of a GP. Food allergies are different to intolerances as they invoke an immune response and usually require medical treatment.