Last November I reported on a review of treatments for irritable bowel syndrome (IBS) that had recently been published in the British Medical Journal (BMJ). The review showed that, of the treatments it assessed, peppermint oil was the most effective.
Fiber was another treatment that was the subject of this review. As the review and my account of it pointed out, fiber comes in two forms: insoluble fiber (for example, wheat bran) and soluble (for example, ispaghul or psyllium fiber derived from plantain). The review found that soluble fiber generally does help IBS symptoms, but insoluble fiber does not.
Recently, the BMJ published a letter that makes reference to this study from Dr. Peter Whorwell, professor of medicine and gastroenterology at Wythenshawe Hospital, Manchester, in the U.K. His letter starts by expressing his surprise at reading in the popular press that, according to the BMJ, fiber is good for IBS.
The original review concluded that insoluble fiber does not make symptoms worse, but as Dr. Whorwell points out, this contradicts his experience in practice. In 1994, Dr. Whorwell coauthored an article in the Lancet that made the case that insoluble fiber is more likely to cause harm than do good. In fact, in his own words, Dr. Whorwell states in his letter “the total exclusion of all cereal fiber, such as bran and brown bread, from the diet is one of the most rewarding treatment strategies I can offer.”
One explanation Dr. Whorwell offers to explain the discrepancy between his clinical experience and the review’s findings is that studies are generally designed to discern if insoluble fiber helps or does not help the symptoms of IBS. Because researchers generally view insoluble fiber as harmless, studies do not necessarily even allow for the possibility that insoluble fiber might actually exacerbate symptoms.
Near the end of his letter, Dr. Whorwell writes, “With evidence-based medicine and the rapid dissemination of research results to the media, we must still listen to what our patients are telling us.”
I suspect that Whorwell knows the value of science, but he appears to understand some of its limitations too. And most importantly, he does seem to be focused on using his experience to help individuals get well.
As doctors, we are generally encouraged to practice evidence-based medicine (EBM). My experience is that doctors tend to take this to mean medicine that has been proven to be beneficial. Doctors who take this view may be shocked, however, to learn just how little of conventional medical practice has been proven to be beneficial.
Also, the term “evidence-based medicine” can blind us to the importance of clinical experience. In fact, in a seminal article published more than a decade ago, the case was put forward for EBM being “about integrating individual clinical expertise and the best external evidence.” 
It seems to me that many doctors (and particularly academics) have got too focused on the external evidence bit and have forgotten the value of clinical experience and expertise. How very refreshing that Dr. Whorwell has not taken this path and is still acutely aware of the importance of listening to his patients.
1. Whorwell PJ. The problem of insoluble fiber in irritable bowel syndrome
British Medical Journal 2009; 338:a3149, doi: 10.1136/bmj.a3149
2. Sackett DL, et al. Evidence based medicine: what it is and what it isn’t. British Medical Journal1996; 312:71–72
Dr. John Briffa is a London-based physician and health writer with an interest in nutrition and natural medicine. His Web site is drbriffa.com