The Role of Fermented Foods, Lactic Acid Bacteria, and Their Metabolites in Combating Viral Infections and Supporting the Immune System

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Introduction

 

Fermented foods and their probiotic components, particularly lactic acid bacteria (LAB) and their bioactive metabolites, have gained increasing attention for their potential in enhancing immune responses and combating viral infections, including respiratory illnesses. In the wake of the recently circulating H5N1 virus that is causing avian influenza in wild birds and some domestic animals we would like to present a comprehensive review of the existing research on the antiviral properties of fermented foods, highlighting their role in immune modulation, inhibition of viral replication, and mitigation of respiratory infections.

The search for non-conventional antiviral agents has led to renewed interest in fermented foods and probiotics. With the emergence of viral pandemics such as COVID-19, and now the threat of Highly Pathogenic Avian Influenzas’ (H5N1), natural dietary interventions have been explored for their potential in enhancing immune defense mechanisms. Fermented foods, rich in probiotic microorganisms, offer significant health benefits through their ability to modulate immune responses, produce antiviral metabolites, and inhibit viral replication(1, 3).

 

Fermented Foods and Their Antiviral Properties

 

Fermented foods, including yogurt, kimchi, kefir, and sauerkraut, contain beneficial probiotic strains, predominantly LAB, that exert antiviral effects through multiple mechanisms(4):

 

  • Enhancing Natural Killer (NK) Cell Activity: LAB stimulate NK cells, improving their ability to target virus-infected cells(2).
  • Modulating Cytokine Responses: LAB upregulate pro-inflammatory cytokines (e.g., IFN-γ, IL-6) essential for an effective antiviral response(3).
  • Competitive Inhibition: Probiotic strains can outcompete pathogenic viruses for adhesion sites in the gut and respiratory tract(1).
  • Production of Antiviral Metabolites: LAB produce bioactive compounds such as lactic acid, bacteriocins, and short-chain fatty acids (SCFAs) that disrupt viral replication(2).

Mechanisms of Action Against Viral Infections

  1. Direct Antiviral Effects

LAB and their metabolites interfere with viral entry and replication by modulating the host’s cellular environment. Some strains have been shown to:

  • Downregulate viral gene expression(1).
  • Inhibit viral attachment to host cells(1).
  1. Immune System Modulation

Probiotic strains contribute to a robust immune defense through:

  • Activation of T-helper cells and cytotoxic T-lymphocytes(3).
  • Enhancement of gut barrier integrity, reducing viral translocation(2).
  • Promotion of systemic immune responses by modulating gut-associated lymphoid tissue (GALT)(4).
  1. Reduction of Respiratory Illness Severity

Clinical studies indicate that individuals consuming fermented foods exhibit:

  • Reduced severity and duration of respiratory infections(3).
  • Enhanced antibody responses to respiratory viruses such as influenza(1).
  • Lower incidence of secondary bacterial infections(2).

Applications in Viral Disease Prevention

COVID-19 and Other Respiratory Viruses

 

During the COVID-19 pandemic, studies suggested that probiotic-rich diets could contribute to reduced viral load and improved recovery rates(1,2). LAB strains such as Lactobacillus rhamnosus and Bifidobacterium bifidum have shown potential in reducing inflammation and mitigating cytokine storms(3).

 

Influenza and Norovirus

Clinical and preclinical studies demonstrate that probiotic supplementation decreases the incidence and severity of influenza and norovirus infections by modulating the mucosal immune response(1).

 

Conclusion

Fermented foods and their probiotic components, particularly LAB, offer promising antiviral properties by modulating immune responses, inhibiting viral replication, and reducing the severity of respiratory illnesses. Further clinical research and large-scale trials are necessary to solidify these findings and integrate probiotic-based interventions into public health strategies.

 

References

  1. Muhialdin, B. J., Zawawi, N., Abdull Razis, A. F., Bakar, J., & Zarei, M. (2021). Antiviral activity of fermented foods and their probiotics bacteria towards respiratory and alimentary tracts viruses. Food Control, 127, 108140. https://doi.org/10.1016/j.foodcont.2021.108140
  2. Kulangara Varsha, K., Narisetty, V., Brar, K. K., Madhavan, A., Alphy, M. P., Sindhu, R., Awasthi, M. K., Varjani, S., & Binod, P. (2023). Bioactive metabolites in functional and fermented foods and their role as immunity booster and anti-viral innate mechanisms. Journal of Food Science and Technology, 60(9), 2309–2318. https://doi.org/10.1007/s13197-022-05528-8
  3. Pyo, Y., Kwon, K. H., & Jung, Y. J. (2024). Probiotic Functions in Fermented Foods: Anti-Viral, Immunomodulatory, and Anti-Cancer Benefits. Foods, 13, 2386. https://doi.org/10.3390/foods13152386
  4. Martin, J. G. P., Lindner, J. D. D., Pereira, G. V. M., & Ray, R. C. (2023). Trending Topics on Fermented Foods. Springer. https://doi.org/10.1007/978-3-031-72000-0

 

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