Having the right balance of bacteria in the body is essential directly for health and immunity for a number of reasons. Probiotics are actually needed for the majority of biological functions, a lot of which have a knock-on affect on immunity.

Crowds out unwanted pathogens

Pathogens in the gut such as yeasts, parasites and detrimental bacteria can only thrive when there is room to do so. Usually, these infections occur after a course of antibiotics. Disruption of probiotic numbers can also be caused by poor diet and stress.

Each organism takes up 1 cell receptor site, which are a little like parking spaces. If these are filled up with probiotics, the detrimental organisms have no where to ‘park’ and pass through the gut. Lactobacillus probiotics also process a substance called lactic acid and other biocides, which destroy unfavourable organisms in the gut, and help to prevent infection.

Lactobacillus acidophilus is particularly useful at preventing the adhesion or ‘parking’ of detrimental organisms and a study concluded that this strain was effective against infections of the urinary tract, the vagina and the gut.  

Promotes nutrient absorption and utilisation

The proper absorption and use of nutrients is essential for the correct function of the immune system. Although all nutrients are needed to some degree for immunity, the main ones are vitamin C, zinc, selenium, B vitamins and vitamin D.

Probiotics help with the absorption of nutrients by producing a substance called short chain fatty acids. These fatty acids are used directly by the cells in the gut wall for their function and repair. Healthy gut cells are needed for proper absorption of nutrients. Probiotics also produce some of these nutrients, contributing towards their level in the body. Studies show that Lactobacillus acidophilus can significantly improve absorption of vitamins and minerals across the gut. 

Influences the development of immune cells

Probiotics have a direct influence on the gut wall, and on a path of tissue called the Gut Associated Lymphoid tissue or GALT for short. The GALT is a house for immune cells, until they are needed in the rest of the body. In the GALT there are immune cells called T and B lymphocytes which help to fight infections. T cells are particularly important for maintaining the balance between immunity, autoimmunity and allergic responses.

Individuals with autoimmunity and allergies have an unbalanced ratio of the many types of T cells. Probiotics have a direct influence on the GALT and the final development of T cells, ultimately promoting immunity and decreasing any autoimmune antibodies. A review concluded that probiotics such as Lactobacillus acidophilus can help promote balance of these immune cells and is particularly useful to those with allergies. 

Influences systemic inflammation

Systemic inflammation is inflammation that affects the whole body. Systemic inflammation results in diseases such as autoimmune diseases, skin diseases etc. This is not to be confused with the inflammation caused by an injury, which is generally localised.

The probiotics within your gut influence the rate of systemic inflammation within your body by influencing your T cells in the GALT. Chronic inflammation triggered by detrimental organisms in the gut wears down immune system function over time and makes it less effective against fighting infections.

What is the gut immunity axis?

The gut-immunity axis is simply the connection between gut function and the immune system. There are many connections between both.

Inflammation and probiotic adherence

High levels of systemic inflammation caused by the immune system can increase the level of inflammation in the gut. A high level of inflammation in the gut does not favour probiotic adherence, and many probiotics may simply pass though.

On the other hand, high levels of inflammation in the gut can be caused by a lack of probiotics and can increase systemic inflammation which effects immunity. In this situation, taking probiotics alongside natural anti-inflammatory agents results in both a reduction in gut and systemic inflammation and preserves health in the long run.

Immunity originally from the gut

Over 70% of your immunity originates from your gut, so gut health and diet is essential. The gut determines the education the immune cells receive. Gut damaging foods such as a high processed diet, alcohol and a high sugar intake directly impacts on immune system function and can promote chronic diseases. Consuming fibre rich foods and 7-9 portions of vegetables and fruit per day provides food for the probiotics and can safeguard health in the long run.