Breath Analysis Can Aid Clinical Characterization of Microbiome Metabolism


Findings were presented at DDW and highlight the feasibility of breath analysis for microbiome metabolic characterization in the digestive system.

Ahmed Tawfike, PhD | Credit: ResearchGate

Ahmed Tawfike, PhD

Credit: ResearchGate

Breath analysis may be a viable alternative to blood collection for the clinical characterization of microbiome metabolism in the digestive system, according to findings from a recent study.

The research was presented at Digestive Disease Week (DDW) 2024 in Washington, DC, this weekend and highlights the feasibility of microbiome metabolic characterization through breath sampling, further suggesting its potential for establishing correlations between metabolites and disease severity and progression as well as investigating the interaction of gut microbiota in response to therapeutic interventions.

“The nutrients we ingest also feed the microbiome that lives in our digestive system,” Ahmed Tawfike, PhD, senior scientist at Owlstone Medical, and colleagues wrote. “The resulting metabolic products may have beneficial or deleterious effects on our health.”

Specifically, investigators cited the association of ethanol and 2-3-butanediol, both produced by carbohydrate fermentation, with non-alcoholic steatohepatitis (NASH), noting that several microbiome-derived metabolites are volatile organic compounds and can be measured in breath. Thus, in the present study, they sought to explore the feasibility of microbiome metabolic characterization before and after carbohydrate or amino acid ingestion.

In total, 13 healthy subjects ≥ 18 years of age weighing ≥ 15 kg (33 lbs) were recruited and instructed to fast overnight and abstain from consuming alcoholic beverages the day before the experiments. Breath samples were collected before and up to 90 minutes after ingestion of 75 g of glucose, cysteine, or tryptophan, with a time resolution of 5 minutes. Compounds of interest were measured using Soft Ionization Flow Tube Mass Spectrometry (SIFT-MS) with direct sampling.

Results showed intraoral swishing of 250 mg/mL glucose in water for 30 seconds, followed by spitting, elicited a peak of ethanol within 10-15 minutes that disappeared after 25-30 minutes. However, ingestion of 300 mL of the same solution showed a variable response among different subjects, with some individuals reaching a peak after 15 minutes and others reaching a peak after 30-50 minutes.

Median baseline levels of ethanol before glucose administration were 99.4 (Interquartile range [IQR], 71.6-182.4) parts per billion. Following glucose ingestion, breath peak levels ranged from 130 - 1600 parts per billion. Similarly, glucose administration induced spikes of acetoin, and propanoic acid, with ranges of 7 - 20 parts per billion and 18-160 parts per billion, respectively.

Administration of tryptophan and cysteine elicited spikes of p-cresol, phenol, and hydrogen sulfide. Additional compounds such as trimethylamine (median, 42.3; IQR, 33.6 - 54.3 parts per billion), methanol (median, 443; IQR, 199 - 531.4 parts per billion), and methane (median, 26988; IQR, 10100 - 76213 parts per billion) were also detected.

Investigators noted these findings support the notion that several metabolites generated by the microbiome in the digestive system can be measured in breath at steady state or after administration of certain substrates, additionally pointing out the ability to replicate this approach in large cohorts to better establish metabolites’ effect on diseases.

“We aim to expand this approach to carbohydrates of different complexity, other amino acids, and nutrients,” investigators concluded.


Tawfike A, Murgia A, Banda I, et al. BREATH-BASED MONITORING OF MICROBIOME METABOLIC RESPONSES BEFORE AND AFTER INGESTION OF NUTRIENTS. Abstract presented at Digestive Disease Week (DDW) 2024 Annual Meeting. Washington, DC. May 17-21, 2024.

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