This article outlines why maintaining a healthy gut is important for our overall health, and suggests how we can maintain the all-important ‘gut microbiome’:

• What is the ‘gut microbiome’?
• Why is our microbiome important?
• What factors affect the health of our microbiome?
• Our gut and our immune system
• Our gut, our diet, and our food choices
• Disease risk associated with an unhealthy microbiome
• What can you do to improve your gut microbiome?

 

What is the ‘gut microbiome’?

Our gut – also known as our ‘gastrointestinal tract’ – processes food from the time it enters our mouth until our body absorbs it, and the unwanted matter is passed out. So gut health (or digestive health as the title suggests) refers to the health and wellbeing of our gut, and how well it processes food.

There are approximately 100 trillion micro-organisms in the human gastrointestinal tract. Collectively they are referred to as the ‘gut microbiome’.

 

 

 

Why is our microbiome important?

Digestive health issues

First, because many of us experience digestive health issues:

• Around 30,000 people in the UK have a serious bowel disease such as ulcerative colitis or Crohn’s disease. Both diseases result in inflammation and swelling of different parts of the digestive tract, and both can be extremely debilitating, and sometimes even life threatening.
• More than one in four adults in the general population of the US, Canada and UK have been shown to have functional bowel disorders such as irritable bowel syndrome (IBS), constipation, and diarrhoea. At any one time, IBS affects about 5% of individuals.
  
• The most common digestive symptoms in the UK include abdominal pain or discomfort, diarrhoea, bloating, flatulence and constipation. 

Ten percent or more of a GP’s working life can be spent in consultation with patients with digestive disorders. CORE: Fighting gut and lover disease

 

Other illnesses

Second, our microbiome is important because gut health problems may be implicated in a number of other illnesses:

• Recent research has found an association between the gut microbiome and risk of developing a number of chronic conditions such as cardiovascular disease, inflammatory bowel disease (IBD), obesity, type 2 diabetes, inflammatory skin diseases such as psoriasis, atopic dermatitis, and autoimmune arthritis.
• The gut microbiome can also impact the central nervous system (CNS) through the ‘gut–brain axis’, an important connection that helps the CNS to develop and mature. It has been shown that neurological conditions such as depression, schizophrenia, anxiety and autism have been associated with an altered gut microbiome. 

Although an association between these two factors doesn’t automatically mean that one causes the other, a cause-and-effect relationship seems possible. More research is needed in this area.

 

 

What factors affect the health of our microbiome?

A number of factors, particularly early in life, may affect how our gut microbiome develops:

• Babies delivered vaginally appear to develop a microbiome with greater amounts of bacteria compared to those delivered by Caesarean section.
• Infants who were formula-fed had fewer bacterial species as compared with those who were breast-fed. The breast-fed group also had a reduced risk of age-related gastroenteritis.
• Insufficient fibre in our diet may result in the loss of certain bacteria from our microbiome. This leads to a decreased production of helpful bacterial metabolites and end products. 

Bacteria were traditionally thought to be harmful to our health, but researchers have found that many bacteria are beneficial. Our gut health benefits from having a diverse range of these ‘good bacteria’.

 

Our gut and our immune system

To put it simply, a healthy gut is a happy gut!

Metabolic disorders

Maintaining a healthy gut is likely to enhance our immune function, reduce gastrointestinal symptoms (like bloating, abdominal pain etc.), improve the absorption of nutrients, and reduce the risk of metabolic disorders. 

Leaky gut

The health of our gut depends on the balance of beneficial bacteria and pathogenic (harmful) bacteria. When the levels of beneficial bacteria decrease, and pathogenic bacteria levels increase, and bacteria may leak through the intestinal wall into the bloodstream. This phenomenon is known as ‘leaky gut’. Leaky gut plays a role in certain gastrointestinal conditions such as coeliac disease, Crohn's disease, and IBS.

Psychiatric disorders 

Leaky gut may also be detrimental to the immune system in diseases such as inflammatory bowel disease (IBD), diabetes, asthma, as well as in psychiatric disorders including depression, anxiety, and autism. However, the scientific community is sceptical as to how harmful this is for most people in practice.

 

Our gut, our diet, and our food choices

As far as the food we eat is concerned, gut health affects our food choices, and our food choices in turn affect our gut:

• Diets high in fat, refined carbohydrates (sugars) and processed foods can cause an imbalance in the gut microbiome and can result in symptoms such as bloating, acidity, and constipation.
• There has been a significant increase in both the incidence and severity of food intolerances and food allergies, particularly in developed countries. Scientists have identified one of the underlying causes as intestinal bacterial ‘overgrowth’: high levels of bacteria which can also cause chronic diarrhoea and malabsorption.
• The gut microbiome also plays a critical role in managing inflammation and immunity, thus helping to protect the body from harmful bacteria that cause infections.
• Another important function of the microbiome is to synthesize vitamin K, B group vitamins, and a number of essential molecules that are fundamental for daily functioning.

 

Food intolerance vs food allergy

It is important to note the difference between these terms:

Food intolerance	Intolerance is a digestive system response. Someone with a food intolerance has difficulty digesting certain foods and has an unpleasant physical reaction to them. Example: lactose-intolerant people may feel nauseous, have stomach pains, or develop diarrhoea or become bloated after drinking milk or milk products such as yoghurt.
Food allergy	An allergy is an immune system response. The gut of someone with a food allergy ‘mistakes’ an ingredient in food as harmful and creates a defence system to fight it. Example: a peanut allergy may cause a rash, itchiness or swelling around the mouth, or it may lead to severe intestinal problems. In extreme cases, a peanut allergy may lead to death.

 

Disease risk associated with an unhealthy microbiome

In a healthy gut, our microbiome interacts with us in a mutually beneficial relationship. Our intestine provides the microbes with nourishment and an environment in which to grow, while the microbes contribute to our homeostasis (a healthy steady state within the body) and are involved in several physiological processes. Disrupting this balance can lead to a range of chronic diseases, such as:

• Obesity: The microbes in the gut play a vital role in digestion, and may also influence whether we become obese or not.
• Type 2 diabetes: There is a specific imbalance in the composition of the gut microbiome in individuals with type 2 diabetes compared with non-diabetic individuals. The specific imbalance was found to be associated with an increased risk of insulin resistance.
• IBS and IBD: In the case of both IBS and inflammatory bowel disease (IBD) large-scale changes have been seen in the abundance and diversity of certain bacteria in the gut.
• Behavioural and cognitive problems: Healthy gut function has been linked to normal functioning of the central nervous system (CNS). In contrast, a disturbed gut microbiome has been linked to behavioural and cognitive problems, including anxiety, depression, and autism.

Some studies have suggested that probiotic supplementation reduces anxiety and depression symptoms with an effect similar to regular prescription medication. 

 

What can you do to improve your gut microbiome?

Here are some practical suggestions for improving the health of your digestive system and for reducing the risk of developing conditions associated with an unhealthy gut:

 

 Useful links for the table:

• Maintaining microbiome homeostasis
• Probiotic-rich foods and fermented foods

 

Reviewed and updated by Elisa Knebel, March 2023

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