Table 1.

Human studies in IBS patients and BCFA levels.

References	Type of Study	Subjects	Samples	Outcomes
Le Gall et al., 2011 [47]	Cohort	UC patients (n = 13). IBS patients (n = 10). Healthy controls (n = 22).	Feces	↑ 2-methylbutyrate, isobutyrate, isovalerate in control vs. IBS group.
Farup et al., 2016 [48]	Case–control	IBS patients (All subtypes, n = 25). Healthy controls (n = 25).	Feces	No statistically significant difference in isovaleric or isobutyric between IBS and control.
Zhang et al., 2019 [49]	Case–control	IBS-D patients (n = 30). Healthy controls (n = 15).	Feces	↑ Isobutyrate IBS-D (no statistically significant different). ↑ Isovalerate in IBS-D correlated with severity of abdominal pain.

UC: ulcerative colitis; IBS-D: irritable bowel syndrome with diarrhea.