Written by Jun Nishihira, M.D., Ph.D..

Confirmation of food safety and efficacy is essential to develop novel functional foods for health promotion. Scientific evidence obtained by clinical trials in humans has been accumulated, and then those food products can be supplied to the market as functional foods after certification by the public (e.g., government) or authorised private organisations. To contribute to maintaining public health and preventing diseases, we have been working on clinical trial over 12 years, and have accumulated large amount of data collecting from more than 100 clinical trials concerning food safety and functionality, and health benefits.

To better understand food safety and efficacy, the data on digestion, absorption, metabolism, and excretion of major compounds in foods are often required. Among a variety of functional foods, we have been working on food function focusing on enhancement of immune system to clarify the defensive action against viral infections, such as influenza. Concerning the food function, it is anticipated that compounds from foods play critical and unique roles in the immune system. For example, b-glucan, the major lipopolysaccharide component of Bifidobacterium cell walls or mushrooms, stimulates the mucosal immunity. These polysaccharides enhance the activities of immune potent cells functioning in both innate immunity and acquired immunity such as macrophages, helper T cells, and cytotoxic T cells to defend the host from gastrointestinal (GI)-tract infection, and also systemic infection.

From a series of studies on the gut microbiota, it becomes clearer that the gut microbiota is deeply linked to the mucosal immunity, not only in the maintenance of GI tract environment, but also in the regulation of the brain functions through brain-gut axis. In this discussion, we mainly focus on functions of probiotics and prebiotics to boost immune system against influenza infection via elevation of antibody titers by influenza vaccination.

Probiotics are defined as live microorganisms that confer a health benefit on the host when administered in adequate amounts. Probiotic bacteria, mainly belonging to the class of lactic acid bacteria (LAB), are known to be beneficial in human and animal health. In particular, lactobacilli are characterised by the production of lactic acid and are commonly used to many vegetable, meat, and dairy fermentations, which favourably affect the gut health. Prebiotics, on the other hand, are known to modulate the number and function of human gut microbiota, and sometimes reduce lifestyle diseases such as diabetes and obesity, in which non-digestible polysaccharides contained in mushrooms promote the growth of preferable gut bacteria for human health. Accordingly, either probiotics or prebiotics, and their combination are expected to boost the immune function beneficial for human health, in concert with commensal gut microbiota.

To prove health benefits of probiotics and prebiotics via the immune system, we performed clinical trials on the efficacy of LAB or Maitake mushrooms in views of prevention from influenza viral infection. One of the suggested methods for assessing immune function in healthy subjects is by vaccine challenge. The vaccine challenge model, potentiating vaccination against influenza, is included in the guidelines on scientific requirements for health claims related to gut and immune function from the European Food Safety Authority.

When an elderly people with a chronic disease suffers from influenza, it often becomes severe, such as complicating pneumonia. To date, we successfully proved that LAB or Maitake mushrooms intake boosted immunity against influenza by the placebo-controlled, double blind clinical studies.^{1, 2} Currently, there is a general consensus that orally administrated probiotic bacteria contribute to the homeostasis of the gut immune system by altering the microbial balance or by interacting with the host immune system. From public health and ethical point of views, all subjects received a vaccine against influenza virus in the study; we should take this into consideration when evaluating the immune-boosting function of an LBA and Maitake mushrooms.

Jun Nishihira is Professor for the Department of Medical Management and Informatics at Hokkaido Information University, Japan

Join Prof. Nishihira at Vitafoods Asia Digital Week

In the Vitafoods Asia Digital Week immune health panel discussion, Prof. Nishihira will introduce the research outcomes on activation of mucosal immunity by LAB and Maitake mushrooms based on the data in our clinical trials. The threat of the new type coronavirus pandemic, COVID-19, is wide-spread in the whole planet. COVID-19 infection is life-threating, particularly in aged people. We expect that intake of LAB or Maitake mushrooms enhances the effect of vaccination against COVID-19 as good as influenza vaccination, leading the reduction of severity and fatality caused by this particular pandemic viral infection.

References

1. Lactobacillus gasseri SBT2055 stimulates immunoglobulin production and innate immunity after influenza vaccination in healthy adult volunteers. Nishihira J, Tomohiro Moriya T, Sakai F, Kabuki T, Kawasaki Y, and Nishimura M. FFHD 2016; 6(9): 544-568

2. Maitake mushrooms (Grifola frondosa) enhances antibody production in response to influenza vaccination in healthy adult volunteers concurrent with alleviation of common cold symptoms. Nishihira J, Sato M, Tanaka A, Okamatsu M, Azuma T, Tsutsumi N, and Yoneyama S. FFHD 2017; 7(7): 462-482