Gut flora and immunity – how are they related?

Specific Health Concern 21 February 2020

For many of us, the winter season is unfortunately a time when we start to feel unwell, take too many days off from work or school and instead end up in an endless string of doctor’s appointments. In this article, I will be explaining exactly how lactic ferments can help you to strengthen your immune defences and avoid these winter mishaps! 

Article by Ariane Monnami, nutritionist and with degrees in Micro-nutrition and Neuro-nutrition. 


A barrier against the outside world… 

Just like our skin, intestinal mucosa constitutes a barrier against the outside world. 

Although it might sound a little strange, our digestive tube can in fact ‘communicate’ with this outside world through its two extremities – it’s a bit like our very own Channel Tunnel! 

The ‘outside’ world

The ‘outside’ world is made of a number of different elements – for example, food at every stage of digestion, gut flora as spoken about in a previous article and other micro-organisms such as viruses, bacteria or fungi. 

The ‘inside’ world 

Of course, there is also the ‘inside’ world! This is made of both lymphatic vessels and blood vessels as well as white blood cells, which all act to ensure our immunity. 

The barrier 

In between these two ‘worlds’, we find the gut barrier, which itself covers a pretty incredible surface area of 250m2 – that’s the same as a tennis court! 

In other words, and what is particular interesting, is that this barrier needs a significant number of ‘defenders’ to protect us against intrusion from unwanted elements such as viruses, bacteria, fungi, undigested bits of food.

Discovering the GALT 

The GALT, or Gut-associated Lymphoid Tissue, is a gut-specific defence mechanism and alone represents an impressive 70% of the immune cells present in our body. 

GALT cells produce a significant number of antibodies and immunoglobulins who have a role to play both locally and on our immune system as a whole.

A developing immune system 

In parallel with gut flora development, the immune system is formed within the first years of birth. For example, increased allergy frequency has been linked to anomalies in the development of gut flora within these first two years and can be affected by things such as birth by Caesarean section, lack of breastfeeding, repetitive use of antibiotics… 


The importance of gut flora 

Our gut contains around 100,000 billion bacteria, about ten to a hundred times more than the number of cells found in our body! 

This gut flora limits the proliferation of pathogenic bacteria (those causing illnesses) and forms a real barrier inside our gut which strengthens and reinforces our own intestinal mucosa. 


Role of lactic ferments 

From educators…

Lactobacilli and Bifidobacteria almost act as ‘teachers’ for the immune cells present in our gut. 

They interact with the GALT, accompanying it in its development process and increasing its effectiveness. 

Lactobacilli stimulate the releasing of immunoglobulines in the gut to prevent bacteria or viruses from entering through the mucosa.  

…to nurturers 

Lactic ferments do not simply act as ‘teachers’, they also ‘nourish’ our gut cells. 

By encouraging the fermentation of undigested fibres, they produce butyrate, a short-chain fatty acid which is also the colon’s preferred energy source. As a result, it strengthens and solidifies the gut barrier. 

‘Adhesive’ bacteria 

Not all lactic ferments are equally effective — 

The Lactobillus Rhamnosus GG strain has been the ‘star’ of over 200 publications and has demonstrated its effectiveness against allergies and in reinforcing the immune system. 

This particular effectiveness is linked to the presence of ‘pili’, almost like a ‘swivelling’ arm which encourages its adhesion to the intestinal mucosa in order to deliver its benefits for our immunity and regeneration of the mucosa. 


When are supplements really worth it? 

Probiotic consumption, in particular Lactobacillus rhamnosus GG is recommended for the following: 

– stimulation of the immune system and prevention of winter illnesses

– rebalancing of gut flora after taking antibiotics / gastro-enteritis

– preventing repeat infections  

– improving allergic responses (immunomodulator functions)  



1. Timmerman HM, Koning CJM, M ulder L , R ombouts FM, B eynen A C – Monostrain, multistrain and multispecies probiotics – A comparison of functionality and efficacy. I nt. J. Food. M icrob. 2004 ; 96 : 219-233.

2. G rangett e C – Probiotiques et immunité. Probiotiques et régulation de la réponse immune allergique et inflammatoire. Cah. N utr. D iet. 2007 ;42(2) : 2S76-85.

3. Heyman M – Probiotiques et immunité. E ffets des probiotiques sur le système immunitaire : mécanisme d’action potentiel. Cah. N utr. D iet. 2007;42(2):2S67-75.