The connection between the gut and the immune system is direct, complex, and widely known. Many integrative healthcare practitioners have likely echoed this statement (or a version of it) to their patients: “It’s estimated that 70 to 80 percent of your immune system resides in your digestive tract.” That explanation to patients often leads to a conversation about the importance of probiotic and prebiotic dietary supplements. The fact is, the scientific literature is filled with papers talking about the gut immune connection and the influence that probiotics/prebiotics can have.

In a 2017 review published in the LymphoSign Journal, the authors identified several key ways in which probiotics, prebiotics, and their metabolic products interact with host immune function including the following specific mechanisms of action:

• Activation of ERK and p38 MAPK pathways
• Reduced LPS-FITC binding and inhibition of NF-kB
• Inhibition of the phosphorylation of ERK, JNK, p38 kinase
• Modulation of TRIF, MAPK, and NF-kB signaling pathways
• Interaction of S layer protein A with DC-SIGN on DCs
• Modulation of NF-kB and MPPK pathways via increased transcription of A20

The 2017 review is consistent with other research demonstrating that probiotics, prebiotics, and the metabolic products they produce impact multiple aspects of both the innate and adaptive mucosal immune system.

The most well-known mechanism of action of probiotics on gut immunity involves the tight junctions in the gut epithelium, which provides the physical barrier between host immunity and the external environment. Several studies have shown that probiotics can enhance epithelial barrier function, which helps support immunity, as well as a healthy inflammatory response.

A 2018 small single-arm pilot study featured in BMC Gastroenterology showed that probiotic supplementation reduced the frequency of circulating Th17 cells and cytokine production.

A 2018 paper published in Probiotics and Antimicrobial Proteins concluded that “Although the cause-effect relationship between pathology and gut microflora is not yet well established, consumption of specific probiotics may represent a powerful tool to re-establish gut homeostasis and promote gut health.”

Supporting immunity begins with a conversation with patients about the gut immune connection and may end with a recommendation of a high-quality probiotic/prebiotic supplement. Fortunately, there are many quality supplements to choose from.

Selected References:

Konig J, Wells J, Cani PD, et al. Clinical and Translational Gastroenterology. 2016;7.

La Fata G, Weber P, Mohajeri MH. Probiotics and Antimicrobial Proteins. 2018;10(1):11-21.

Singh A, Sarangi AN, Goel A, et al. BMC Gastroenerology.2018;18:85.

Vieira AT, Teixeira MM, Martins FS. Frontiers in Immunology. 2013;4:445.

Wu RY, Jeffrey MP, Johnson-Henry KC, et al. LymphoSign Journal. 2017;4:1-24.