The Role of Guar Fiber in Improving the Management of Irritable Bowel Syndrome, Functional Constipation, and Functional Diarrhea

Guar fiber is a soluble fiber that has been used for symptom management of irritable bowel syndrome (IBS), functional constipation (FC), and functional diarrhea (FD). However, the effect of guar fiber supplementation on symptom management is currently unclear. The aim of this review is to determine the effect of guar fiber supplementation compared with any other nutrition intervention on gastrointestinal (GI) symptoms with individuals diagnosed with IBS, FC, and FD. A secondary aim is to determine the dosage of guar fiber supplementation required to elicit an improvement in associated symptoms. A systematic review (CRD42022374730) was performed with literature from inception. PubMed, EMBASE, CINAHL, and Web of Science were searched on October 28, 2022, to identify eligible studies which reported guar fiber supplementation in patients diagnosed with IBS, FC, and/or FD using the Rome criterion. Findings were synthesized narratively. Study quality was assessed using the Johanna Briggs Institute quality assessment tools. Nine articles reported on stool consistency, defecation frequency, laxative use, bloating, abdominal pain, flatulence, and quality of life (QOL). All pre-post studies (n = 5) reported statistically significant improvements for GI symptoms and QOL. Two of 4 randomized controlled trial studies reported improvements in GI symptoms when supplemented daily with 5 to 6 g of guar fiber for 4 to 12 weeks. Our study shows that guar fiber supplementation appears effective in improving symptom management of IBS and FC with a 5-g/d dosage most used. Future studies are required to more clearly understand the benefits of guar fiber supplementation and elucidate dosing strategies. This review provides the grounds for further well-designed studies to investigate the impact of guar fiber supplementation in populations with IBS, FC, and FD.