摘要：Aims: The aim of this study was to examine diurnal variation in the concentration of methane in the breath of methane producers and to clarify the mechanism of methane production in enterobacterial flora. Subjects and methods : The study was performed on 11 methane producers (students) with a methane concentration of 5 ppm or more in their breath. Methane in the breath and hydrogen concentrations were measured simultaneously using an exhalation gas analyzer, and diurnal variations were followed. Results : Four diurnal variation patterns were observed in 11 methane producers. Pattern A, methane varies at a higher concentration than hydrogen; pattern B, methane and hydrogen vary in parallel at almost the same level; pattern C, hydrogen varies at a higher concentration than methane; and pattern D, methane concentration varies at a low level of 5 ppm or less. In the case of patterns A and B, the concentrations of methane and hydrogen were in a positive correlation (p<0.02). From the standpoint of dynamic correlation with variations in concentration (-ppm and +ppm), a significant correlation in variations of methane and hydrogen existed in pattern B only (p<0.01). Conclusion : Methane producers comprise those of pattern A, where methanogens are preponderant; pattern B, where methanogens exist together with hydrogen-producing bacteria; and pattern C, where methanogens are inferior. In the case of pattern B, the concentration of methane and hydrogen varies in mutual correlation.Key words: Methane in breath, methanogens, methane producers, diurnal variation type, enterobacterial flora
