How do probiotics boost immunity?

Scientists have discovered that up to 70 or 80% of our immune cells are actually located in our gut and that there is an intricate relationship between the bacteria in our gut and our immune system.¹

Immune system 101

The immune system is a collection of cells, substances and processes that work together to protect the body from being attacked by undesirable bacteria, fungi, parasites, viruses, and toxins. The immune system can be divided into two main systems, or lines of defence. These are known as innate immunity and adaptive immunity.

Innate immunity is our first line of immunological defence against foreign substances. It is a rapid immune response, initiated within minutes or hours of encountering an intruding pathogen and can defend us against a wide range of invaders.

Adaptive immunity, on the other hand, is specific. It has the capacity for memory, which enables our bodies to initiate a more rapid and efficient immune response each time we are exposed to the same invading pathogens.⁵

Probiotics have the ability to affect both the innate and adaptive immune responses by modifying the functions of different immune cells.³

Ways probiotics support immune function

There are several ways that probiotics can help to boost immunity and support the healthy functioning of our immune systems.

• Preventing the growth of ‘bad’ bacteria - Probiotics are able to prevent the growth of undesirable bacteria in the gut by competing with them for nutrients.²
• Stopping ‘bad’ bacteria from taking hold in the gut – probiotics, or the ‘good’ bacteria compete with ‘bad’ bacteria for space to attach to the walls of the gut.³ The ability of an invading bacteria to stick to the gut wall is the first important step for any infection to take hold.⁴
• Destroying ‘bad’ bacteria - probiotics are able to produce organic acids and antimicrobial compounds called bacteriocins which have the ability to inhibit ‘bad’ bacteria.²
• Reducing inflammation - taking probiotics causes a shift in the make-up of the gut flora toward specific beneficial bacteria, which are known to produce anti-inflammatory substances in the gut.²
• Protecting the intestinal barriers - probiotics have been shown to strengthen the intestinal barrier – a layer of cells and mucous which prevents foreign substances (including micro-organisms, allergens and toxins) from entering the body²

A clinical trial on probiotics for immunity found that healthy, active adults who took Bifidobacterium animalis lactis Bl-04 were less likely to come down with an upper respiratory tract infection⁶ like the common cold.⁷

References

1. Wiertsema SP, et al. The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies. Nutrients. 2021; 13(3): 886.
2. Galdeano CM, et al. Beneficial effects of probiotic consumption on the immune system. Ann Nutr Metab. 2019; 74: 115–124.
3. Yan F, Polk DB. Probiotics and immune health. Curr Opin Gastroenterol. 2011; 27(6): 496–501.
4. Chen X, et al. The Female Vaginal Microbiome in Health and Bacterial Vaginosis. Front Cell Infect Microbiol. 2020; 11: 631972.
5. Marshall J, et al. An introduction to immunology and immunopathology. Allergy Asthma Clin Immunol. 2018; 14(Suppl 2): 49.
6. West NP, et al. Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clinical Nutrition. 2014; 33(4): 581-587.
7. Healthline. Acute Upper Respiratory Infection. Healthline. 2020. https://www.healthline.com/health/acute-upper-respiratory-infection#What-is-acute-upper-respiratory-infection? – accessed 26-May-22