Gut Microbiota

The word microbiota refers to the population of microorganisms that live on or in the human body, including bacteria, archaea, yeast and viruses.

In the gastrointestinal tract there are at least as many bacterial cells as there are human cells in the whole of the body – this cluster of microorganisms is referred to as the gut microbiota. This vast microbial population is important not just for nutrient digestion but also for health maintenance. Consequently, there is extensive international research into the composition and activity of the gut microbiota and its influence on health.

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The gut microbiota: 

• Weighs about 0.2 kg

• Has a gene set approximately 150 times larger than the human gene set

• Has a genome that is over 99% from bacteria, representing more than 1,000 different species 

• Distribution is determined by pH, oxygen availability, nutrient availability and transit time.

Role of the gut microbiota

Although it is not possible to define a healthy gut microbiota, the complex relationship between the number, activity and diversity of both beneficial and harmful bacteria in a healthy intestine is what makes up a balanced gut microbiota.


The balanced gut microbiota has several important functions including;

• Fermentation of non-digestible dietary fibre

• Production of short-chain fatty acids

• Vitamin K2 production

• Prevention of colonisation of pathogenic microorganisms

• Modulation of intestinal epithelial cell proliferation

• Development and homeostasis of the immune system

Factors Affecting Microbiota

Factors affecting the gut microbiota

Maintaining a balanced gut microbiota is key, as harmful bacteria can have more damaging effects in the gut, such as promoting the formation of carcinogenic substances and producing toxins. Disturbance in the balanced gut microbiota, known as dysbiosis, is associated with several conditions including inflammatory bowel diseases and metabolic diseases, such as diabetes. 

Each individual has a unique gut microbiota, and only about 40% of these genes are shared with any other person. 

There are a range of factors that affect the composition of the gut microbiota, including diet, age, smoking, physical activity, medication and stress.


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