Breath volatile organic compounds for the gut-fatty liver axis: Promise, peril, and path forward

Table 2 Exhaled breath uniquely captures the entire output of the gut liver axis in the context of a person

Gut flora	Lumen factors	Hepatic factors	Host
Bacterial diversity and function	Barrier integrity	Enzyme heterogeneity (e.g., alcohol dehydrogenase)	Diet
Mucosal or lumen associated	Immune defense	Liver disease	Medications
Location	Mucosal disease (e.g., celiac, crohns)	Cirrhosis and porto-systemic shunting	Co-morbid conditions (e.g., diabetes)
(e.g., small bowel, right colon)
	Transit time		Age, gender, body mass index