In the human gut, a subpopulation of the microbiome belonging to Archaea produces methane through fermentation. Increased methane production is associated with gastrointestinal discomfort and disorders, and 20% of the healthy Western population exhales high methane levels, indicating high gut methane production. However, the mechanisms and health effects are unclear. To learn more, a recent study analysed 100 healthy young adults who were divided into high methane emitters and low methane emitters according to breath analysis. 16S rRNA sequencing revealed that the microbiomes of high and low emitters had different diversity levels and different compositions. Notably, the relative abundance of the archaeon Methanobrevibacter smithii was 1000-fold higher in high emitters than in low emitters, and M. smithii in the high emitters co-occurred with dietary fiber-degrading bacteria, including Ruminococcaceae and Christensenellaceae. Metagenomics and metabolomics revealed that high emitters had increased gut levels of metabolites such as formate and acetate. These metabolites were strongly related to dietary habits, such as vitamin, fat, and fiber intake, as well as to microbiome function. Although further research in other demographics is needed, the findings illuminate the complex interactions leading to two different gastrointestinal states and identify potential therapeutic targets for methane-associated disorders.