Introduction
This is not really an Arduino module but links to a stand alone sensor that measures methane (CH4) and Hydrogen (H) as a way to analyze gut functions. This could be achieved with the xSpectre spectrometer by adding a breathing component that analyse the spectral absurbance of the gas flow.
https://foodmarble.com/product/foodmarble-aire-2/
BBC NEWS Europe 20230604, Lara Lewington explores the latest tech keeping track of gut health.
https://www.bbc.co.uk/programmes/m001mqwt