Gastrointestinal Tolerance and Microbiome Response to Snacks Fortified with Pea Hull Fiber: A Randomized Trial in Older Adults

BACKGROUND: Consuming foods with added fiber may help older adults achieve fiber recommendations; however, many high-fiber ingredients have little effect on laxation and may contribute to unpleasant gastrointestinal side effects. OBJECTIVES: The aim of the study was to determine the effects of consuming snacks fortified with pea hull fiber (PHF) on stool frequency and form, gastrointestinal symptoms, and appetite in older adults. An exploratory aim was to determine if PHF altered the microbiota profile. METHODS: A 10-wk, randomized, blinded, crossover study was carried out. Following a 2-wk baseline period, participants [aged (mean ± SD) 69.7 ± 6.5 y; n = 31; 14 men, 17 women] consumed snacks providing 10 g/d of PHF or a control, each for 2-wk periods followed by 2-wk washouts. Participants used the Bristol Stool Form Scale (BSFS) to record daily stool frequency and gastrointestinal symptoms, and completed the Gastrointestinal Symptom Rating Scale (GSRS) and Simplified Nutritional Appetite Questionnaire (SNAQ) biweekly. One stool was collected per period for 16S ribosomal RNA high-throughput amplicon sequencing of the fecal microbiota profile. RESULTS: Participants reported 1.63 ± 0.05 stools/d and 76.6% normal transit stool form at baseline and no change with PHF. GSRS syndrome scores were similarly unchanged. Daily abdominal noises and bloating were higher for PHF versus control, and flatulence was higher for PHF versus baseline, suggesting fermentation in some individuals. There was no evidence to suggest a common PHF-induced microbiome response for the group as a whole; however, a subgroup of participants (n = 7) who responded with increased flatulence (fermenters), harbored many different taxa than nonfermenters, and demonstrated lower abundance of Clostridiales with PHF. Appetite was unchanged with PHF. CONCLUSIONS: PHF did not modulate stool form or frequency in older adults with normal bowel habits. Because snacks fortified with PHF did not suppress appetite, PHF may be an appropriate fiber source for older adults at nutritional risk. Microbiome profile may be predictive of gastrointestinal symptom response to PHF. This trial was registered at www.clinicaltrials.gov as NCT02778230.