Niigata University reveals that Rice-koji is effective in alleviating stress in mice: Suppression of anxiety and pain

Associate Professor Keiichiro Okamoto and Assistant Professor Yoshito Kakihara of the Graduate School of Medical and Dental Sciences of Niigata University, in collaboration with Hakkaisan Brewery Co., Ltd. and Niigata Agricultural Research Institute Food Research Center, announced that rice-koji extracts alleviate anxiety and pain resulting from psychophysical stress. Using mouse and cultured cell models, the research group demonstrated that ergothioneine, an amino acid contained in rice-koji, regulates the excitability and functional expression of cranial nerves that process information about anxiety and pain. The findings are expected to lead to the development of methods to alleviate stress and were published on September 14 in the international scientific journal Nutrients.

Foods made from fermented rice have been consumed since the Nara period and are gaining attention as a healthy diet because they contain a wide range of nutrients. Amazake and sake are also made using rice-koji. While recent research has revealed that it contains a functional component effective for alleviating stress, whether or not the daily consumption of rice-koji-containing foods could alleviate stress was unknown. In this study, rice-koji extract or ergothioneine contained in the extract was orally administered daily to mice under stress. This was provided by Hakkaisan Brewery Co., Ltd.

The results of behavioral tests showed that behaviors associated with stress-induced anxiety and pain were reduced. Furthermore, this stress-reducing effect may occur by improving the excitability of neurons in areas that process anxiety and pain information, such as the hypothalamus, the nucleus raphe magnus of the medulla oblongata, and the lumbar spinal cord. Experiments using human neuron-like cells revealed that rice malt extract or ergothioneine affects functional expression at the cellular level, such as regulating the expression of neurotrophic factor.

Through this, the researchers scientifically proved the benefit of one of the traditional dietary habits of the Japanese. They will further pursue the development of safer simple stress alleviation methods by examining the stress-alleviating effect of rice-fermented foods, which are flagship products of Niigata Prefecture.

According to Okamoto, "We have been focused on researching rice-derived foods and health promotion. In Japan, rice-fermented foods have been consumed since ancient times, and many are considered to have health promoting effects. In the current study, we reported that rice-koji alleviates anxiety and pain induced by stress, using model mice and cultured cells. Verifying our findings in humans is important."

Journal Information
Publication: Nutrients
Title: Preventive Roles of Rice-koji Extracts and Ergothioneine on Anxiety- and Pain-like Responses under Psychophysical Stress Conditions in Male Mice
DOI: 10.3390/nu15183989