The Microbiome and gut health

The Microbiome and gut health

The human gut microbiome and its role in health are the subject of extensive and ongoing clinical research. What we do know is that the microbiome is involved in fundamental metabolic, nutritional and immune system functions. That’s why it is so important to protect the microbiome and support its continued healthy balance¹.

So what exactly is the gut microbiome?

The human microbiota consists of the 10-100 trillion symbiotic microbial cells harboured by each person, primarily bacteria in the gut; the human microbiome consists of the genes these cells harbour ² . A typical digestive tract contains a vast collection of microbial communities, including³:

Bacteria	Yeasts	Viruses	Archaea	Fungi

The gut contains more than 1000 bacterial species. And that’s a good thing, because a diversity of bacteria in the gut is associated with stability and resilience, which is a reliable indicator of gut health. ⁴ And, interestingly, research has shown that the composition of the gut microbiome can change with dietary intervention,⁵ stress levels ⁶ and quality of sleep⁷.

The Microbiome and gut health

The Microbiome

and gut health

So what exactly is the gut microbiome?

The human microbiota consists of the 10-100 trillion symbiotic microbial cells harboured by each person, primarily bacteria in the gut; the human microbiome consists of the genes these cells harbour. A typical digestive tract contains a vast collection of microbial communities, including:

Bacteria

Yeasts

Viruses

Archaea

Fungi

The gut contains more than 1000 bacterial species. And that’s a good thing, because a diversity of bacteria in the gut is associated with stability and resilience, which is a reliable indicator of gut health. And, interestingly, research has shown that the composition of the gut microbiome can change with dietary intervention, stress levels and quality of sleep.

Differentiating between ‘microbiome’ and ‘microbiota’

Based on the recent advances in the area, a paper published by Berg et al⁸ on June 30th 2020 recommends the revival of the original definition of the microbiome term suggested by Whipps et al⁹. Berg et al explain that, ‘The definition, which contains all important points that are valid even 30 years after its publication in 1988, was extended by two explanatory sentences differentiating the terms microbiome and microbiota’:

Definition of microbiome

The microbiome is defined as a characteristic microbial community occupying a reasonably well-defined habitat which has distinct physio-chemical properties. The microbiome not only refers to the microorganisms involved but also encompass their theatre of activity, which results in the formation of specific ecological niches. The microbiome, which forms a dynamic and interactive micro-ecosystem prone to change in time and scale, is integrated in macro-ecosystems including eukaryotic hosts, and here crucial for their functioning and health.

Definition of microbiota

The microbiota consists of the assembly of microorganisms belonging to different kingdoms (Prokaryotes [Bacteria, Archaea], Eukaryotes [e.g., Protozoa, Fungi, and Algae]), while “their theatre of activity” includes microbial structures, metabolites, mobile genetic elements (e.g., transposons, phages, and viruses), and relic DNA embedded in the environmental conditions of the habitat.

What influences the balance of the gut microbiome?

Gut microbiota are unique to each individual. Their composition is influenced by various factors – some of which we can control, and others we can’t.

For example, when a baby is born, the delivery method can influence maternal-offspring exchanges of microbiota. In the womb, if the unborn baby is exposed to antibiotics, this can also affect their gut microbiome¹⁰.

Throughout life, people can support the balance of their gut microbiome by making healthy lifestyle choices, such as the food they eat and how much exercise they get ¹¹.

For more information about factors that influence the balance of the gut microbiome, please download our gut microbiome factsheet.

The role of the microbiome in health and illness

In healthy bodies, the gut microbiota perform a number of key functions:

Metabolism

Fermenting non-digestible food components (mainly dietary fibre) to produce short-chain fatty acids that are important for maintaining a healthy colon¹².
Synthesis of essential nutrients, including B vitamins¹³.
Release/stimulation of important neurotransmitters, such as dopamine and serotonin¹⁴.

Immunity

Gut-associated lymphoid tissue is highly specialised and is the main entity of mucosal-associated lymphoid tissue, representing ~70% of the entire immune system.
Gut microbiota inform the immune system in establishing a balance between tolerating/responding to potential threats¹⁴.

Protection

The microbiota act as a structural barrier, preventing pathogen adhesion and subsequent colonisation¹⁵.

The circadian rhythm-microbiome-metabolism connection

Understanding dysbiosis

When the microbiome becomes imbalanced, this is known as ‘dysbiosis’ and can be defined as:¹⁶

An increase in potentially harmful microbes
Loss of microbial diversity
Loss of beneficial microbes

Dysbiosis can be implicated in the pathophysiology of gastrointestinal disorders^17,18and other metabolic conditions ¹⁹.

What causes dysbiosis?

Dysbiosis may be caused by medication (e.g. antibiotics) ^{20, 21}, bacterial infections (e.g. gastritis)²², stress²³, and lack of sleep²⁴.

To find out more, please download our factsheet about how the gut microbiome affects health, including links to key review papers.

The link between the gut and the brain

Unlike with other organs of the body, communication between the gut and the brain appears to be a two-way affair. This two-way communication is believed to occur via various routes²⁵.

Neural

Vagus nerve and spinal cord

Endocrine

HPA axis

Immune System

Production of cytokines

Metabolism

Short-chain fatty acids interact with enteroendocrine cells to produce neuropeptides

How people can support their own gut microbiome health

There are various lifestyle factors that can influence the health of the gut microbiome. These include:

Diet

In terms of diet, variety and diversity are key. The focus should be on plant-based nutrition, and should include polyunsaturated and monounsaturated fats, and proteins from foods such as fish, poultry, beans and nuts. Artificial sweeteners and alcohol should be consumed in moderation. Experimenting with fermented foods is recommended, for example cultured milk products and yogurt ²⁶. Food supplements containing live bacteria are also a popular way of supporting the microbiome. For more information on what to recommend to your patients, download our nutrition and the microbiome article – written by registered dietitian Laura Tilt.

Exercise

Lack of exercise may have an important influence on shifts in microbial populations. A study showed that professional athletes had an increase in the diversity of their gut microbial populations in response to exercise and diet 6.

Stress levels

Stress has an impact on colonic motor activity via the gut-brain axis, which can alter gut microbiota profiles. Activities such as yoga and meditation have been demonstrated to reduce the effects of stress on the body ^27,28. People who wish to help promote a healthy balance of their gut microbiome may find using techniques such as yoga and meditation to reduce their stress levels beneficial.

Quality and quantity of sleep

A study has shown that short-term sleep loss induces subtle effects on the human microbiota 10. This points to the role of sleep in gut health. Good quality sleep is an integral part of a healthy lifestyle. And a healthy diet, regular exercise and techniques to reduce stress all contribute to enjoying a better quality of sleep.

Smoking

Smoking has a significant negative influence on gut microbiota composition.⁶ Therefore, alongside all the other known health reasons to quit, the best advice is to aim to give up smoking as soon as possible to help promote a healthy gut microbiome. People should consult their doctor if they need assistance in quitting.

Recommending a food supplement to help balance bacteria in the gut

Alongside recommending a healthy diet and lifestyle, food supplements can be used to help promote a healthy balance of bacteria in the gut.

There are certain things to consider when recommending a food supplement:

Has it demonstrated a benefit in clinical trials and in the population of interest?

Does it provide an effective dose, as shown by research studies that have used the product?

Is it adequately labelled with:

Full strain names, e.g. Lactobacillus acidophilus NCIMB 30175
Concentration
Storage instructions
Administration instructions
Recommended dose

Is the strain level fully characterised?

Has its viability and functionality through the gut been established?

Does it contain any ingredients that may be unsuitable for certain people, such as:

Dietary fibre
Lactose
Added sugars
Allergens (e.g. casein)

Useful resources

The circadian rhythm-microbiome-metabolism connection

Are you aware of the interdependence between the circadian rhythm and the microbiome?

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