Changes in Microbiota and Short-Chain Fatty Acids Following 3-Month Pilot Intervention Study Feeding Brown Rice Ball (Omusubi) to Healthy Volunteers

Abstract

Background: The health effects of brown rice are still in debate. From September to December 2019, 30 employees in the Ministry of Agriculture, Forestry, and Fisheries conducted the pilot intervention study on bowel movement, intestinal microbiota, fecal short-chain fatty acids, and inflammatory biomarkers to see the health effects.
Subjects and Methods: Brown rice genmai onigiri (rice cake) was provided 5/week as a business lunch for 12 weeks. Participants practiced the pre-and post-questionnaires, daily life records, monthly blood pressure measurements, and body composition. Before and after the intervention, the fecal samples were used for the simultaneous measurement of intestinal microbiota and short-chain fatty acids. Biochemical data involving IL-6, CRP, and TNFa were obtained for correlation analysis with microbiota changes.
Results and Discussion: The body weight decreased in about half the participants, and bowel movements and stool status improved significantly. Dominant microbiota were Firmicutes (around 65%), Actinobacteria (15-17%), Bacteroidetes (5-7%), and less than 1% of Proteobacteria, Verrucomicrobia, and Fusobacteria. Significant microbiota change was an increase in Actinobacteria and a decrease in Proteobacteria. Verrucomicrobia and Fusobacteria also tended to decrease. In short-chain fatty acids, acetate and propionate grew to decline, while n-butyrate and i-valerate slightly increased.
Acetate, propionate positively correlated with IL-6, and n-butyrate, and n-valerate showed a positive correlation with IL6 and CRP. Isobutyrate and isovalerate negatively correlated TNFα. The upper tertial of genmai eaters showed beneficial effects.
Conclusion: Replacement of one meal per day to brown rice omusubi showed health benefits in more than half of the participants. The relationship between bacterial species and short-chain fatty acids suggested the holistic control of SCFA and inflammatory biomarkers.