Effects of a brown rice-derived supplement on physical, cognitive and mental health among adults and the role of the gut microbiota: study protocol for a longitudinal, double-blind, randomized, placebo-controlled trial

The consumption of brown rice, which contains bran and germ and is rich in fiber, micronutrients, and phytochemicals, can contribute to good physical, cognitive, and mental health. However, these health benefits and the relevant mechanisms have not been fully elucidated, especially in human subjects. Therefore, we will conduct a randomized controlled trial to examine the effects of a brown rice-derived supplement on various aspects of health and to elucidate the underlying mechanisms. This study will be a prospective, longitudinal, double-blind, randomized, placebo-controlled trial. Eighty healthy adults aged 20 to 64 years will receive 3.5 g/day of a brown rice-derived supplement or placebo for 12 weeks. We will assess immune-related and metabolic markers using transcriptome and metabolome analyses of blood samples, respectively, and evaluate the gut microbiota composition using stool samples, including 16S rRNA-based analysis, with short-chain fatty acids also measured. Cognitive function, constipation, sleep, mood state, and health-related quality of life will also be assessed using validated assessments at baseline and at the endpoint. Between-group comparisons will be conducted using appropriate statistical methods according to the distribution and characteristics of the data. This study is the first to examine the effects of a brown rice-derived supplement on various aspects of health, including immune, cognitive, physical and mental health. We hypothesize that changes in the variation in the gut microbiota play a key role in the mechanisms underlying these health effects; therefore, we will investigate how changes in the gut microbiota caused by the consumption of the brown rice-derived supplement affect health status. We hope that the information derived from this study will be useful for promoting the use of brown rice-derived supplements as a healthy food and improving public health. University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), UMIN000049330. Registered on 8 November 2022. https://rctportal.niph.go.jp/en/detail?trial_id=UMIN000049330