Effect of immune responses on breath methane dynamics

D, Polag, F. Keppler

Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 236, D-69120 Heidelberg 

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Methane (CH4) which can be detected in human breath has long been exclusively associated with anaerobic microbial activity (methanogenesis) in the gastrointestinal tract. However, recent studies challenge this understanding by revealing that CH4 might also be produced endogenously in cells through oxidative-reductive stress reactions. To evaluate the effects from immune responses triggered by infections, inflammations, and induced perturbation by vaccination on CH4 dynamics in breath, two subjects were monitored over a period of almost two years. Breath CH4 levels were measured by gas chromatography equipped with a flame-ionization detector. Both subjects exhibited significant deviations (positive and negative, respectively) from their normal CH4 breath levels during periods of potential enhanced immune activity. Deviations from the “‘healthy state” were indicated by the exceeding of individual CH4 ranges. Moreover, for the first time we could clearly prove CH4 degradation induced through vaccination by measuring stable carbon isotopes of CH4 using gas chromatograph – combustion – isotope ratio mass spectrometry.  

The observed individual breath CH4 dynamics supports the hypothesis that CH4 has a potential bioactive role in immunology. An exceeding of breath CH4 levels from normal level may be used to detect significant changes in ROS levels and oxidative stress, and could potentially be used to classify immune responses. Therefore, breath CH4 may be used as an additional diagnostic tool in the field of system biology and precision medicine. Although this study cannot clarify whether the observed CH4 dynamics following immune reactions are solely driven by the generation of ROS or controlled by microbes, or a combination of both, it highlights CH4 as an in vivo parameter that might for example provide substantial benefits in classifying the efficacy of vaccination.