Defined literally, immunity is a defense system people are naturally equipped with to avoid epidemics. It works to keep the body healthy by repairing any damaged tissue and attacking foreign pathogens such as bacteria and viruses entering the body. This system includes two types of immunity: “innate immunity” and “adaptive immunity.” Adaptive immunity is further divided into “hormonal immunity,” in which antibodies play a central role, and “cellular immunity,” The focus is the cells responsible for carrying immunity.

What kind of effect does fermented food have on immunity? It is well known that fermented foods contain countless numbers of bacteria. The dead bacteria serve as food for the living bacteria in the gut, regulating intestinal health and stimulating immunity cells. Meanwhile, living bacteria travel to the intestines, and the metabolites help to create an acidic environment. In addition, fermented foods are rich in vitamins, proteins, sugars, and other nutrients and have an antioxidant effect. The appeal of fermented foods is this healthy balance. The variety of bacteria taken into the body plays their respective roles in improving immunity and invigorating the body overall.

A Japanese saying says, “there is no need for a doctor if you have miso,” referring to the many ways in which miso can invigorate the body. Liquid products that have been brewed and their solids removed, such as soy sauce and sake, have most of their bacteria killed through heat sterilization in the manufacturing process. On the other hand,  Miso is left as is, and therefore a variety of positive effects from the remaining bacteria can be expected. Additionally, while the salt concentration is high, the desired result of increased blood pressure is addressed by peptides in miso that act to cancel out the effects of the additional salt content.

If made to be excessive, a person’s immune response then becomes an allergic reaction, which is never a desirable outcome. Therefore, the implications of a runaway allergic reaction associated with “boosting” immunity can be avoided by rephrasing it as “stabilizing” immunity. Incidentally, brewed products have a degranulation inhibiting effect (or an effect of preventing allergies) provided by the rice peptides and soy peptides produced by koji mold. Thus, fermented foods play various roles in maintaining the body safely and healthily. It stands to reason that they have such a long and continuing history.