prebiotics, probiotics and the microbiome

Prebiotics, Probiotics and the Microbiome. Whats it all about?

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The Microbiome

We have all heard the term ‘gut health’. 

Another term you may have heard of is the ‘microbiome’. This is the presence of  bacteria, fungi and viruses living all over our body.

The mouth and genito-urinary system for e.g host a microbiome, as well as our skin! 

So whilst the microbiome is not just restricted to our gut, the gut microbiome has emerged as a big influencer on our health. 

The Gut Microbiome. 

Our gut contains roughly 100 trillion microorganisms, of which about 1.5kg are bacteria! 

These bacteria compete for space and resources (food) against one another. 

The good bacteria in the gut are called probiotics. 

We feed them via undigested food termed prebiotics, we will come to those further down the article. 

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AKA ‘Good Bacteria

Probiotics are defined as “a living microorganism that produces beneficial effects on the health of the host person”.

Good bacteria benefit our health when our gut microbiome is in equilibrium. To achieve this, a healthy diet is needed. 

When good bacteria eat, fermentation of the food occurs which produces short chain fatty acids, ‘SCFAs’. 

These SCFAs are responsible for some of the beneficial effects of probiotics on our health. 

Probiotics are found in lots of every day foods. Examples of foods that naturally contain helpful bacteria are yoghurts* and fermented foods such as kimchi, sauerkraut and miso soup. Other examples are kefir, kombucha tea, and some types of unpasteurised pickles and picked vegetables.

Unfortunately poor eating habits, stress and excessive antibiotic consumption** can compromise the good bacteria’s activity/ alter their composition. This creates an imbalance that puts our health at risk.

*With yoghurt, try and look for low fat with no added sugars if possible!

**Antibiotics are very important and necessary at times. If you are prescribed antibiotics, try and bump up your fibre(prebiotic) and yoghurt (probiotic) intake! Probiotics need prebiotics to survive.



To keep these good bacteria alive and thriving, food is required. 

So what do the good bacteria eat? They eat prebiotics. 

Prebiotics are essentially indigestible fibres that reach our gut intact. Selectively, the good bacteria in the gut feed off these indigestible fibres(prebiotics). 

To qualify as a prebiotic, at least three criteria are required.

  1. It must not be absorbed/ digested in the stomach.
  2. It must be selective for the good bacteria i.e bifidobacteria and/or lactobacilli
  3. Fermentation of the substrate muse(prebiotic) induce beneficial effects locally (i.e in the gut) or systemically (in the body).

Prebiotics in our diet

The most common prebiotic is inulin, which is found in garlic, leaks and bananas.

Cholestero-Low also contains inulin! 

Other prebiotics in our diet include oats, bran, onion, garlic, banana, kiwis and chickpeas. 



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Whats all the fuss about ?

Notably, there has long been evidence connecting fibre to longer healthier lives.

Denis Burkitt, was a surgeon who spent time working in Africa. He noted that there was an absence of conditions such as diabetes, hypertension(blood pressure) and  high cholesterol in people in their 40’s and 50’s in Africa in the 1960’s compared to their counterparts in England.

He was not the first person to identify this, but became a relative champion for the connection between lack of fibre in “western diets’ and its association with chonic disease. 

The importance of fibre continues to be studied. Some of its benefits occur by providing these probiotics in our gut the food to thrive. 

When fibre is fermented in the gut by microbes, short-chain fatty acids (SCFAs) are produced. These SFCA’s are important for gut health as well as triggering other healthy benefits in the body such as immunity and lowering cholesterol. 

Where does it go wrong?

Lack of fibre in our diet over a period of time has been identified as significant contributor to many ‘modern’ illnesses.

With a diet lacking or low in fibre, the good bacteria have little to eat. The composition or quality of the microbiome changes from a healthy pattern to one that associated with disease or predisposition to disease. 

Conditions associated with a poor gut health include obesity, type 2 diabetes, bowel cancer, inflammatory bowel disease, obesity, the metabolic syndrome.

It’s important to highlight, that these conditions are multifactorial in origin, and are not just caused by imbalance of gut health. Genetic predisposition, environment, stress, diet etc can all be contributors. Indeed they may all interact to lead to the development of these conditions. 

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So what are the benefits of having a healthy gut ?


The research in this area is still at the very early stages for the most part and sometimes at the hypothesis stage.

Cholesterol Lowering 

One benefit of a healthy gut could be in lowering your cholesterol.

The mechanism is not fully understood, though it is thought that SCFA’s effect cholesterol metabolism in the liver via bile acid synthesis

Gut Health

  • Irritable Bowel Syndrome: Thought to occur by enhancing the immune system’s barrier functions, helping fight inflammation, reducing gas production by improving the guts good bacteria and by reducing the sensitivity to gas buildup. 
  • Constipation:In the gut, probiotics lower the pH of the colon which might help stool move faster. 
  • Diarrhoea: By replenishing the good bacteria of the gut. 


Immune function

SCFA’s have been shown to regulate some of the mediators of immunity and inflammation such as interleukins and cytokines. 

In the gut, SCFA production reduces the pH of the gut which inhibits the growth potential of potentially pathogenic bacteria such as Clostridium species.  


Diabetes and glucose regulation

Regulation of glucose in a positive manner is thought to occur via SCFA signalling to liver cells.


This occurs via the gut feeling fuller than it is as a result of fibre, plus possible modulation of leptin via SCFA’s which a hormone that regulates appetite

Vitamin Production 

The gut microbiome can produce Vitamin B and K! Vitamin B is important for a our nervous system. The key enzyme needed to produce Vitamin B12, is only found in bacteria! 

Brain Health 

Exchanges between the gut and brain occur via blood circulation, the vagus nerve, and the blood brain barrier. The probiotics produce positive metabolites such as SCFA’s, serotonin, dopamine. 


Essentially via the mechanisms mentioned above, as well as aiding constipation.  Here is an interesting article on yoghurt and its benefits in healthy ageing. 

So what can you do?

Don’t stress! This is where we go back to basics.

How much fibre do you think you eat everyday?

Ideally we need at least 30gm of fibre per day as a adult, though most of us only eat about 18g. 

Throughout the day, try and incorporate some fibre and natural probiotics into your diet.

Oats, porridge, weetabix, all-bran, yoghurt*,kefir, miso soup, garlic, leaks, asparagus, beans/ pulses (think ‘beans, beans good for your heart, the more you eat the more you fart!’), lentils, fresh or dried fruits, potatoes with the skin.

*With yoghurt, go for the low fat, no added sugar versions if possible! 

Cholestero-Low has oat beta-glcuan and inulin for your heart and gut. 

We hope you enjoyed this blog!  

Please let us know you thoughts in the comment section! 

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