Bowel habits, fecal microbiota, and fecal bile acid composition of healthy adults consuming fruit pomace fibres: Two-arm, randomised, double-blinded, placebo-controlled trials

Dietary fiber modulates gastrointestinal (GI) health and function, providing laxation, shifting microbiota, and altering bile acid (BA) metabolism. Fruit juice production removes the polyphenol- and fiber-rich pomace fraction. The effects of orange and apple pomaces on GI outcomes were investigated in healthy, free-living adults. Healthy adults were enrolled in two double-blinded, crossover trials, being randomized by baseline bowel movement (BM) frequency. In the first trial, subjects (n=91) received orange juice (OJ, 0g fiber/d) or OJ + orange pomace (OJ+P, 10g fiber/d) for 4 wk, separated by a 3-wk washout. Similarly, in the second trial, subjects (n=90) received apple juice (AJ, 0g fiber/d) or AJ + apple pomace (AJ+P, 10g fiber/d). Bowel habit diaries, GI tolerance surveys, and 3-d diet records were collected throughout. Fresh fecal samples were collected from a participant subset for microbiota and BA analyses in each study. Neither pomace interventions influenced BM frequency. At wk 4, OJ+P tended to increase (p=0.066) GI symptom occurrence compared to OJ, while AJ+P tended (p=0.089) to increase flatulence compared to AJ. Faecalibacterium (p=0.038) and Negativibacillus (p=0.043) were differentially abundant between pre- and post-interventions in the apple trial, but were no longer significant after FDR correction. Baseline fiber intake was independently associated with several microbial genera in both trials. Orange or apple pomace supplementation was insufficient to elicit changes in bowel habits, microbiota diversity, or BA of free-living adults with healthy baseline BM. Future studies should consider baseline BM frequency and habitual fiber intake.