Gut health

The gut (also known as the digestive system, gastrointestinal tract or gastrointestinal system) is made up of a group of organs: the mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas and gallbladder, and is home to your unique gut microbiome (GM).

The gut's primary function is to absorb nutrients from the food we eat, and excrete waste. The body will use the nutrients containing vitamins, proteins, fats and calories in order to carry out essential jobs around the body that contribute to a person’s overall physical and mental wellbeing. 

The gut, when it’s healthy, can work harmoniously, but when it has a bacterial imbalance - also known as gut dysbiosis - it can lead to unpleasant, physical symptoms. Aside from gut bacteria, some people may suffer with long-term inflammatory digestive disorders or autoimmune disorders of the gut such as Crohn's disease or ulcerative colitis and may also benefit from nutritional therapy.

There is also a growing body of evidence that suggests what we eat and the health of our gut microbiome (directly related to our food intake and lifestyle) can have a significant impact on our mood and even the prevalence of a mental health condition. 

Let’s look at the gut in more detail.

The gut microbiome

Health nutritionist Charlotte Turner explains in her article, ‘What is a healthy gut microbiome’ that our guts consist of trillions of live bacteria.

Our gut microbiome refers to all the bacteria and microorganisms that exist within our small and large intestines. We have a mini-ecosystem of 100 trillion active bacteria, yeasts, fungi, viruses, and protozoans in our digestive tract.

The gut microbiome bacteria is represented by three different groups:

  • Good/beneficial bacteria
  • Potentially harmful bacteria (if the right environment)
  • Bad/pathogenic bacteria

Our gut microbiome or GM is unique to each individual and has quickly developed a neurological network that sends messages to the brain, through the vagus nerve connecting the gut and brain. Not only is it physically connected to the brain, our GM also influences our immune system function, our weight and problematic digestive issues such as irritable bowel syndrome.

Your gut microbiome is fragile, and with modern day advancements, stresses and busy lifestyles encroaching on our health, sometimes the gut microbiome takes the brunt. For example, if you have been on a prolonged course of antibiotics, your good and bad bacteria may both have been killed off by the medication.  

Functional medicine practitioner and nutritionist Rosie Letts suggests replenishing your gut bacteria with healing foods such as homemade bone broth, protein and fermented foods (miso, sauerkraut, kefir etc.).

L-glutamine is the most abundant of the amino acids that serve as building blocks for protein in the body. It plays an important role in a number of biochemical processes and is involved in more metabolic processes than any other amino acid. Because it fuels white blood cells and other rapidly dividing body cells, glutamine is indispensable to immune system function and tissue repair. 

How does the gut work?

Food moves through the gut in five main progressive stages:

  1. Mouth – In the mouth, the teeth begin the digestive process by tearing and grinding solid food into sizeable pieces. Saliva then begins to break down the food into enzymes. 
  2. Esophagus - The soft mass of chewed food in the mouth is then swallowed. The esophagus (tube leading to the stomach) squeezes the partly digested food to the stomach by contracting in a wave-like motion known as peristalsis. This process takes less than six seconds. 
  3. Stomach - The stomach muscles contract to mix the food with hydrochloric acid and digestive enzymes, secreted from the gastric glands. These digestive juices break down the proteins, sugars and fats found in food.
  4. Small intestine - The partly digested food is then squeezed from the stomach through the duodenum and into the small intestine. Here, bile from the liver begins to emulsify fat and digestive juices from the pancreas continue to digest nutrients. Villi on the wall of the small intestine increases the surface area and aids the absorption of smaller molecules into the bloodstream.
  5. Large intestine - By the time the food leaves the small intestine, most of the nutrients will have already been absorbed. Next, the resulting lump of mostly digested food moves slowly through the colon. This is the last stage of absorption, leaving only a mass of fibre and bacteria. Because this mass of waste cannot be used by the body, it is finally excreted through the anus.

Common gut health issues

A gut health problem is a change or abnormality in the natural functioning of the digestive process.

Problems with your gut health or digestive conditions are extremely common. As many as 40% of the UK population suffer from at least one symptom of a digestive problem at any one time and can negatively impact a person’s quality of life.

The terms gut health problem or digestive condition cover a large variety of conditions, symptoms and diseases that affect your gut.

Types of digestive problems include:

Can digestive problems be serious?

Most digestive problems are very mild and can be cured quickly and easily with the help of a nutrition professional or managed with diet and by taking appropriate medication.

However some gut health problems are considered to be very serious and vary in cause, and are not related to your gut microbiome. These can be diagnosed by identifying ‘red flag symptoms’.  You can ask five simple questions to help identify red flag symptoms:

  • Have you noticed a sudden and drastic change in the functioning of your bowels?
  • Have you recently lost weight for no reason?
  • Do you have difficulty swallowing?
  • Have you noticed an increase in heartburn or stomach pain?
  • Have you noticed bleeding from your back passage?

If you experience one of more of these symptoms, it is advisable to visit your GP as soon as possible.

Gut health and your mental health

The gut has often been dubbed ‘our second brain’, and the phrase “that gut feeling” may have more truth to it than we originally thought.  Several studies have suggested that gut dysbiosis could contribute towards feelings of low mood and even mild depression

Scientists refer to the gut-brain connection as the microbiome-gut-brain axis, a chemical pathway using neurotransmitters to send direct messages between the central nervous system and the gut. 

Certain species of bacteria found in a healthy GM aid the production of neurotransmitters in the brain such as serotonin, our happy hormone and it’s estimated that 90% of serotonin is made in the gut. If our gut bacteria is out of balance, we may struggle to regulate our moods.

In this article ‘Good gut health and your mental health’ we delve into how food can be used to support a healthy gut and aid improved moods.

If you're interested to find out more about the gut-brain connection, Harley Street nutritionist Rhiannon Lambert chatted to Happiful on the I am. I have podcast about the food and mood connection.

I am. I have - with Rhiannon Lambert

Rhiannon Lambert I am. I have

Listen Now


How can a nutrition professional help with gut health?

Good nutrition and professional guidance can support your gut health in a number of ways, whether diagnosed with a condition or not.

In your first session, a nutrition professional will discuss your symptoms, diagnosis (if applicable), lifestyle and dietary choices, plus work through your relationship with food to gain a clear picture of your current diet. They will make recommendations if further investigation is needed - such as tests that GPs can organise - and work with you to draw up individual, tailored plans that support a diagnosis or unpleasant symptoms.  

With nutrition and diagnosed conditions such a Crohn’s disease or ulcerative colitis, there is no one size fits all method, and studies have shown that although diet can’t cure these conditions, it can help to calm your symptoms and allow you to lead a more comfortable lifestyle. 

Like many aspects of nutrition, knowledge is key, and this is particularly relevant to gut health in understanding how the gut affects our overall wellbeing. A nutrition professional can provide recommendations that are individualised to encourage a healthy, happy lifestyle.





Further help


Related topics

Looking for help?
Find a nutritionist
Would you like to provide feedback on our content?

Find a nutritionist dealing with digestive problems

All therapists are verified professionals.

Related Articles

More articles