RESEARCH · July 29, 2014
TAKE-HOME MESSAGE
- Authors reviewed literature from MEDLINE, EMBASE, and the Cochrane Controlled Trials Register through December 2013 and identified 14 randomized controlled trials that included 906 patients with irritable bowel syndrome (IBS) evaluated for treatment with fiber. Pooled relative risk of remaining symptomatic after treatment with soluble fiber (not bran) was 0.86 (95% CI, 0.80–0.9).
- Results indicate a benefit in treating IBS with soluble fiber. Bran was neither beneficial nor harmful.
Expert Comment
Primary Care
David Rakel MD, FAAFP
Probiotics and Soluble Fiber Work for IBS
These systematic reviews and meta-analyses published in the latest issue of the American Journal of Gastroenterology look at two therapies for irritable bowel syndrome. Ford et al reviewed the effect of probiotics and Moayyedi et al reviewed the effects of fiber. Both were found to be beneficial and may share a synergistic effect. Let’s review some terms.
Probiotics are live microorganisms that have a positive effect on health.
Prebiotics are undigested foods that probiotics needs to live and reproduce. Fiber is a prebiotic.
Synbiotics are combinations of a probiotic and a prebiotic. Synbiotics are often found in a nutritional supplement and can contain a variety of probiotic species with a prebiotic such as inulin.
Dysbiosis is an imbalance of healthy and unhealthy bacteria (eg, Clostridium difficile colitis following antibiotic therapy).
To simplify, think of it this way:
Probiotic (microorganism) + prebiotic (fiber) = synbiotic = a synergistic therapeutic effect
A probiotic cannot sustain itself without a prebiotic, which is best obtained through a high-fiber, plant-based diet.
The review by Ford and colleagues showed ~21% therapeutic response over placebo with probiotics for IBS. The number needed to treat (NNT) was 7, and the number needed to harm (NNH) was 35, with no significant side effects. Because this was a meta-analysis of pooled data, the authors were unable determine which probiotics are most beneficial; however, it appears that Lactobacillus, Bifidobacterium, Saccharomyces (a yeast), Streptococcus, and Escherichia coli all showed benefit.
The review by Moayyedi and colleagues showed that soluble fiber improved IBS symptoms by about 17% (RR, 0.83) over placebo with a NNT of 7. Psyllium was found to have the greatest benefit.
When fiber and bacteria are combined, fermentation ensues, which produces short-chain fatty acids (SCFA) such as butyrate, acetate, and propionate. These SCFA are the main source of energy for the enterocytes and help keep inflammation in check while repairing the gut lining. Using both a probiotic and prebiotic may have a synergistic effect not only for IBS but also for the overall health of the GI ecosystem.
Therapeutic summary for IBS
- Consider a probiotic that contains Lactobacillus and Bifidobacterium species at a dose of at least 108 colony-forming units (CFU) daily for 1 month. Then encourage fermented foods as a continued source of probiotics, such as yogurt, miso, and sauerkraut.
- Consider psyllium (1 tbsp in 8–10 oz of water) one to two times daily for 1 month, then encourage a soluble-fiber rich diet through the regular consumption of vegetables, high-fiber grains, and fruit.
- Be sure to address the mind–body connection by encouraging stress reduction.
References
Ford AC, Quigley EM, Lacy BE, et al. Efficacy of prebiotics, probiotics, and synbiotics in irritable bowel syndrome and chronic idiopathic constipation: systematic review and meta-analysis [published online ahead of print July 29, 2014]. Am J Gastroenterol. doi:10.1038/ajg.2014.202.
Moayyedi P, Quigley EM, Lacy BE, et al. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis [published online ahead of print July 29, 2014]. Am J Gastroenterol. doi:10.1038/ajg.2014.195.
ABSTRACT
OBJECTIVES
Fiber has been used for many years to treat irritable bowel syndrome (IBS). This approach had fallen out of favor until a recent resurgence, which was based on new randomized controlled trial (RCT) data that suggested it might be effective. We have previously conducted a systematic review of fiber in IBS, but new RCT data for fiber therapy necessitate a new analysis; thus, we have conducted a systematic review of this intervention.
METHODS
MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched up to December 2013. Trials recruiting adults with IBS, which compared fiber supplements with placebo, control therapy, or “usual management”, were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy as well as number needed to treat (NNT) with a 95% confidence interval (CI).
RESULTS
We identified 14 RCTs involving 906 patients that had evaluated fiber in IBS. There was a significant benefit of fiber in IBS (RR=0.86; 95% CI 0.80–0.94 with an NNT=10; 95% CI=6–33). There was no significant heterogeneity between results (I2=0%, Cochran Q=13.85 (d.f.=14), P=0.46). The benefit was only seen in RCTs on soluble fiber (RR=0.83; 95% CI 0.73–0.94 with an NNT=7; 95% CI 4–25) with no effect seen with bran (RR=0.90; 95% CI 0.79–1.03).
CONCLUSIONS
Soluble fiber is effective in treating IBS. Bran did not appear to be of benefit, although we did not uncover any evidence of harm from this intervention, as others have speculated from uncontrolled data.
Related Items
Prebiotics, Probiotics, and Synbiotics in IBS and Chronic Idiopathic Constipation
The American Journal of Gastroenterology
The Effect of Fiber Supplementation on Irritable Bowel Syndrome: A Systematic Review and Meta-analysis
Am. J. Gastroenterol 2014 Jul 29;[EPub Ahead of Print], P Moayyedi, EM Quigley, BE Lacy, AJ Lembo, YA Saito, LR Schiller, EE Soffer, BM Spiegel, AC Ford