May 17, 2016
2 min read

Fiber moderately effective in chronic idiopathic constipation, with side effects

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Fiber supplementation is moderately effective for treating chronic idiopathic constipation, but also causes moderate gastrointestinal side effects, according to the results of a systematic review and meta-analysis.

“Chronic idiopathic constipation is a common symptom-based disorder,” Stephanos Christodoulides, MSc, a doctoral researcher at the Wingate Institute for Neurogastroenterology and GI Physiology Unit, Center for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, told Healio Gastroenterology. “Fiber supplements are commonly used and are recommended as first-line management strategy,” however, “there has been no definitive quantitative summary of available evidence on the efficacy of fiber.”

Therefore, Christodoulides, along with Mark Scott, PhD, and colleagues searched relevant literature published up to February 2016, and included seven randomized controlled trials of fiber supplementation vs. placebo in a total of 430 adults with chronic idiopathic constipation in their analysis. The outcomes of interest included the effects of fiber supplementation on global symptom response, stool output, gut microbiota composition and adverse events.

The included studies were “of variable methodological quality and high risk of bias,” and used different fiber types and doses, Christodoulides said. Treatment periods also varied (2-8 weeks) as did the proportion of women in each trial (64-100%).

Mark Scott

They found that 77% of 147 patients randomly assigned to receive fiber supplementation responded to therapy compared with 44% of 140 patients who received placebo (RR = 1.71; 95% CI, 1.2-2.42). The overall number needed to treat with fiber to result in response in one patient was 3 (95% CI, 2.6-3.4).

Fiber also significantly increased stool frequency (standardized mean difference, 0.39; 95% CI, 0.03-0.76) and softened stool consistency (SMD, 0.35; 95% CI, 0.04-0.65) compared with placebo. However, fiber was also found to significantly increase flatulence compared with placebo (SMD, 0.56; 95% CI, 0.12-1).

“Overall, fiber is moderately effective, with a dose-dependent effect, but with moderate dose-dependent gastrointestinal side effects (eg, flatulence),” Christodoulides said. “It remains unclear which type of fiber is the most efficacious, although the most robust evidence seems to be for psyllium (a soluble, non-prebiotic fiber).”

The researchers acknowledge that none of the included studies had a low risk for bias, which could negatively impact the interpretation of results, nor did any follow an intention-to-treat analysis, which could result in overestimation of efficacy. GRADE criteria also showed evidence was of low quality.

“These findings provide a robust analysis of the effect of fiber supplementation on chronic idiopathic constipation allowing for health service provision planning and future guideline development,” Christodoulides said. “Fiber supplementation is a reasonable first-line therapy albeit with the caveat of increased gastrointestinal adverse events, such as flatulence, and warrants discussion with the patient prior to institution.” – by Adam Leitenberger


Disclosures: The researchers report no relevant financial disclosures.