Novel index for assessing the intestinal environment in prebiotic-supplemented healthy adults via non-invasive gas analysis.

The composition of intestinal gas, a metabolic product of the gut microbiota, may reflect the state of the intestinal environment. However, conventional gas measurement methods are challenging because of their high invasiveness. Therefore, we aimed to analyze the changes in intestinal gas composition and gut microbiota following prebiotic intervention using a novel system-that can non-invasively collect intestinal gas released during daily defecation. We propose a new index for intestinal environment evaluation based on intestinal gas and gut microbiota relationships. Healthy adults consumed inulin and galactooligosaccharides daily for 7 weeks. Intestinal gas was collected for 3 weeks before the intervention and during the last 3 weeks of the intervention. Fecal samples were collected in week 2 before the intervention and week 6 of the intervention. Following intervention, hydrogen and carbon dioxide gases increased significantly, whereas methanethiol decreased significantly. Although not significant, a decreasing trend in hydrogen sulfide was also observed. We proposed an "intestinal gas ratio index (fermentation-to-putrefaction gas ratio)", demonstrating its strong correlation with dynamic changes in the gut microbiota, particularly the relative abundance of Japanese beneficial bacteria and sulfur-based gas-producing bacteria, and bacterial diversity. Overall, this index serves as a non-invasive functional marker for evaluating the intestinal environment.