Soluble Fiber May Be Effective for Symptoms of IBS

Laurie Barclay, MD

September 09, 2009

September 9, 2009 — Soluble fiber (psyllium) may effectively relieve symptoms of irritable bowel syndrome (IBS), but insoluble fiber (bran) may worsen symptoms, according to the results of a randomized, placebo-controlled trial reported in the August 28 Online First issue of the BMJ.

"In the management of irritable bowel syndrome, dietary advice is often given," write C.J. Bijkerk, MD, from University Medical Center Utrecht in Utrecht, the Netherlands, and colleagues. "Most general practitioners recommend an increase in the fibre content of the daily diet, through the addition of insoluble fibre in the form of bran. Furthermore, approximately half of patients with irritable bowel syndrome receive drug treatment, often including psyllium based supplements."

The goal of this study was to evaluate the efficacy of increasing the dietary content of soluble fiber (psyllium) or insoluble fiber (bran) in patients with IBS.

In a general practice setting, 275 patients aged 18 to 65 years with IBS were assigned to 12 weeks of treatment with 10 g of psyllium (n = 85), 10 g of bran (n = 97), or 10 g of placebo (rice flour; n = 93). The main outcome of the study was adequate symptom relief during at least 2 weeks in the previous month. To determine both short-term and sustained efficacy, this outcome was measured after 1, 2, and 3 months of treatment. Secondary outcome measures were IBS symptom severity score, abdominal pain severity, and IBS quality-of-life scale.

Compared with the placebo group, the psyllium group had a significantly greater proportion of responders during the first month (57% vs 35%; relative risk [RR], 1.60; 95% confidence interval [CI], 1.13 - 2.26) and the second month of treatment (59% vs 41%; RR, 1.44; 95% CI, 1.02 - 2.06). During the third month of treatment only, bran was more effective than placebo (57% vs 32%; RR, 1.70; 95% CI, 1.12 - 2.57). However, this was not statistically significant in the worst-case analysis (RR, 1.45; 95% CI, 0.97 - 2.16).

Symptom severity in the psyllium group was reduced by 90 points after 3 months of treatment vs 49 points in the placebo group (P = .03) and 58 points in the bran group (P = .61 vs placebo). Quality of life was similar in all 3 groups. The 3-month treatment period was completed by 54 (64%) of the patients assigned to psyllium, 54 (56%) in the bran group, and 56 (60%) in the placebo group.

"Psyllium offers benefits in patients with irritable bowel syndrome in primary care," the study authors write. "Early dropout was most common in the bran group; the main reason was that the symptoms of irritable bowel syndrome worsened."

Limitations of this study include selection bias affecting generalizability, incomplete patient blinding, and high dropout rate.

"The benefit of psyllium may be somewhat greater in patients who fulfill the Rome II criteria for irritable bowel syndrome," the study authors conclude. "Bran may worsen symptoms of irritable bowel syndrome, especially at the beginning of treatment, and should be advised only with caution."

The Netherlands Organisation for Health Research and Development provided peer-reviewed funding for this study. Pfizer BV, the Netherlands, delivered psyllium for this study. The study authors have disclosed no relevant financial relationships.

BMJ. 2009;339:b3154. Abstract

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