Breath volatilome as a new tool to study nutrition-host-microbiota interactions: the example of kombucha intake and psychological stress level

Details

Supervisors

Delzenne, Nathalie M.

Faculty

Faculté de pharmacie et des sciences biomédicales

Degree label

Master [120] en sciences biomédicales, à finalité spécialisée: nutrition humaine

Abstract

enIntroduction: Analysis of exhaled volatile compounds – the breath volatilome – is a promising non-invasive approach for studying human physiology. These compounds, which originate from the environment or endogenous metabolism, may also reflect the activity of the gut microbiota. This master's thesis studies in vivo the impact on the breath volatilome (1) of the ingestion of kombucha – a fermented birch-based tea with potential health benefits – in healthy volunteers and (2) of psychological stress levels. The aim is to discover markers reflecting the interaction between human metabolism and the gut microbiota through breath analysis. Materials and methods: In the kombucha study, five healthy fasting volunteers (two women, three men; 20 [19; 21] years old) participated in two days of testing to compare kombucha consumption with water consumption (control). Several breath samples were collected before and up to 360 minutes after ingestion. In the stress study, conducted by the CICN, 70 volunteers (48 women, 22 men; 31 [24; 46] years old) selected on the basis of a score above 14 on the Perceived Stress Scale (PSS) provided a single fasting breath sample to compare moderate and high stress levels. Both studies used selected ion flow tube mass spectrometry (SIFT-MS), enabling untargeted volatilome profiling and targeted quantification of specific compounds. Results: The kombucha study showed changes in breath composition appearing 5 minutes and 120 minutes after kombucha consumption. The transient peak of several compounds (such as ethanol and lactic acid) 5 minutes after ingestion was thought to be due to kombucha residues in the upper gastrointestinal tract. The stress study did not reveal any overall change in breath composition based on stress level, but showed a reduction in the concentrations of specific metabolites already observed in the volatilome of more stressed volunteers, such as ethyl acetate and xylene isomers, as well as new compounds such as butyric acid, which may indicate a decrease in associated butyrate-producing bacteria. Conclusion: This master's thesis confirmed that breath analysis can detect changes related to kombucha consumption and psychological stress. In the future, such an approach could enable personalised, real-time monitoring of diet and its impact on stress-related physiological responses.