In a systematic review and meta-analysis of 48 randomized controlled trials, investigators from McMaster University in Ontario, Canada, found that peppermint oil and certain types of dietary fiber are more effective than placebo for relieving symptoms of IBS.
Peppermint oil, which has been found to have antispasmotic properties, showed the most significant effect in four trials. The patients in those trials were 67% less likely to experience persistent IBS symptoms following peppermint oil therapy than subjects following a regimen of placebo treatment. However, the pool of 392 patients from those four trials was the smallest of the treatment categories covered in the meta-analysis, so further research is needed.
Peppermint oil, which has been found to have antispasmotic properties, showed the most significant effect in four trials.
The researchers identified similar but less pronounced positive effects when analyzing 22 trials of antispasmotic drugs. These were roughly a third more likely to be associated with diminished symptoms. The quality of evidence supporting the antispasmotic products was more variable than the evidence supporting peppermint oil. The strongest evidence was associated with the drug hyoscine, also known as scopolamine, a drug used to treat motion sickness.
The review of twelve trials of dietary fiber suggested a 13% lower risk of persistent symptoms, but closer analysis indicates that not all fiber is created equal. In particular, five studies of bran (an insoluble fiber) indicated no significant benefit compared to placebo or to a low fiber diet. However, six trials of 321 patients found that symptoms were 22% less likely to persist following treatment with ispaghula husk (a soluble fiber) than placebo.
So what is an IBS patient to do? The most appropriate choice of treatment may depend on which of the many symptoms associated with IBS are present. Antispasmotic drugs are typically most effective for managing IBS-related diarrhea; the laxative properties of ispaghula husk are more commonly employed in addressing constipation.
The results of the meta-analysis were e-published on Nov. 13 by the British Medical Journal.