Efficacy of different dietary fibers for chronic idiopathic constipation: a systematic review and network meta-analysis

Clinical Snapshot

Key Findings

• P Value: Not reported in abstract

• Effect Size: Not reported in abstract; SUCRA rankings used as surrogate for comparative ranking probability

• Primary Outcome: Viscous soluble fibers were associated with greater efficacy compared with placebo in relieving defecation difficulty (high certainty, GRADE Class 1); improvements in stool consistency and stool frequency relative to placebo were also observed (moderate certainty, GRADE Class 1)

• Nnt Or Sensitivity: NNT not calculable from available data; SUCRA rankings indicate viscous soluble fibers had highest probability of favourable performance for straining (moderate certainty), stool frequency (low certainty), and stool consistency (low certainty); insoluble fibers ranked highest for overall constipation symptom scores (very low certainty)

• Confidence Interval: Not reported in abstract

Clinical Application

Dietary fiber supplementation is widely accessible, low-cost, and generally safe. Viscous soluble fibers (e.g., psyllium/ispaghula husk) are available over-the-counter and as prescription items. Practical implementation requires patient education on adequate fluid intake and gradual dose titration to minimise bloating and flatulence. Symptom-oriented fiber selection is feasible in primary care settings. Psyllium husk (ispaghula), a viscous soluble fiber, is available in Australia both over-the-counter (e.g., Metamucil) and on the Pharmaceutical Benefits Scheme (PBS) for certain indications. The TGA classifies bulk-forming laxatives including psyllium as complementary medicines or listed medicines depending on formulation. RACGP guidelines for constipation management recommend dietary fiber as a first-line intervention, consistent with this review's findings. Australian GPs and gastroenterologists can reasonably apply the finding that viscous soluble fibers (particularly psyllium) are supported by higher-certainty evidence for symptom-specific outcomes, while noting that insoluble fiber products (e.g., wheat bran) may be preferred by some patients for global symptom relief, albeit with very low certainty evidence. Dietitian referral for individualised fiber counselling aligns with Australian chronic disease management frameworks. Adults with chronic idiopathic constipation (CIC) without identified secondary cause; findings are not directly applicable to constipation-predominant IBS, opioid-induced constipation, or constipation in paediatric or elderly populations without further evidence

Abstract

This study aims to compare the efficacy and safety of different dietary fiber subtypes in treating patients with chronic idiopathic constipation (CIC) through network meta-analysis (NMA). PubMed, Embase, Cochrane Library, and Web of Science were searched from inception to October 23, 2025. The risk of bias was evaluated using the Cochrane RoB 2.0 tool, and treatment rankings were calculated using the surface under the cumulative ranking curve (SUCRA). 17 randomized controlled trials (RCTs) involving 1423 adults with CIC were included. NMA suggested that viscous soluble fibers were associated with greater efficacy compared with placebo in relieving defecation difficulty (high certainty, class 1), and were also associated with improvements in stool consistency and stool frequency relative to placebo (moderate certainty, class 1). According to SUCRA rankings, viscous soluble fibers tended to have a higher probability of favorable performance compared with other dietary fiber subtypes in improving straining during defecation (moderate certainty), stool frequency (low certainty), and stool consistency (low certainty), and was associated with a relatively favorable tolerability profile (moderate certainty). Insoluble dietary fibers showed the highest ranking probability for improvement in overall constipation symptom scores; however, this finding was supported by very low certainty evidence. Overall, the findings suggest that viscous soluble fibers have a higher probability of improving stool consistency, stool frequency, and straining during defecation. In contrast, insoluble fibers showed a relatively higher ranking for improvement in overall constipation symptom scores. These results support a symptom-oriented and individualized approach to dietary fiber selection in the management of CIC.

References

1. 1.Mou, J., Zeng, L., Li, Y., Sun, M., Li, Q., Hu, K., & Wang, Q. (2026). Efficacy of different dietary fibers for chronic idiopathic constipation: a systematic review and network meta-analysis. Food & Function. https://doi.org/10.1039/d6fo00286b