Epidemiological study on the effects of gut microbiota and nutrients on breath hydrogen and methane concentrations

Breath hydrogen concentration measurement is a valuable tool for assessing the intestinal environment; however, few epidemiological studies have investigated the relationship between exhaled hydrogen and gut microbiota in healthy subjects. This study aimed to epidemiologically elucidate the relationships between exhaled hydrogen, gut microbiota, and nutrient intake in healthy residents of the Iwaki area of Hirosaki City, Aomori Prefecture, including those who exhaled methane. We categorized participants into low- and high-exhaled hydrogen groups based on the median exhaled hydrogen concentration of 6.13 ppm and matched background factors by propensity score matching for age, body mass index, and defecation habits. In the high exhaled hydrogen group, intestinal butyrate-producing bacteria such as <i>Faecalibacterium</i>, <i>Anaerostipes</i>, and <i>Roseburia</i> increased, and <i>Bacteroides</i> strains decreased. In addition, the group with high exhaled hydrogen concentrations had a high dietary fiber intake, and positive correlation was observed between dietary fiber intake and butyrate-producing bacteria. This trend was particularly pronounced for soluble dietary fiber. The exhaled methane concentration decreased in the higher exhaled hydrogen concentration group, and intestinal <i>Methanobrevibacter</i> was positively correlated with the exhaled methane concentration, although in extremely small amounts. No significant relationship was found between each nutrient intake and <i>Methanobrevibacter</i> strain. Measurement of the exhaled hydrogen concentration is useful for assessing the intestinal environment associated with nutritional intake. However, methane gas production was not changed by dietary intake, suggesting that intervention with prebiotics may be necessary.