BMJ letter reminds doctors of limitations of science and the importance of clinical experience

Last November I reported on a review of treatments for irritable bowel syndrome 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. One of the other treatments that was the subject of this review was fibre. As the review and my account of it pointed out, fibre comes in two forms: insoluble fibre (e.g. wheat bran) and soluble (e.g. ispaghula/psyllium fibre derived from plaintain). The review found that soluble fibre generally does help IBS symptoms, but insoluble fibre does not.

Today, the BMJ published a letter which makes reference to this study from Professor Peter Whorwell, professor of medicine and gastroenterology at Wythenshawe Hospital, Manchester in the UK. His letter starts by expressing his surprise at reading in the popular press that, according to the BMJ, fibre is good for IBS. The original review concluded that insoluble fibre does not make symptoms worse, but as Professor Whorwell points out, this contradicts his experience in practice. In 1994 Professor Whorwell co-authored an article in the Lancet which made the case that insoluble fibre is more likely to cause harm than do good. In fact, in his own words, Professor Whorwell states in his letter that ‘the total exclusion of all cereal fibre, such as bran and brown bread, from the diet is one of the most rewarding treatment strategies I can offer.’

One explanation Professor 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 fibre helps or does not help the symptoms of IBS. Because researchers generally view insoluble fibre as harmless, studies do not necessarily even allow for the possibility that insoluble fibre might actually exacerbate symptoms.

Near the end of his letter, Professor 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. As an academic Professor Whorwell I suspect knows the value of science, but he appears to understand some of its limitations too. And most importantly of all, he does seem to be focused on using his experience to help individuals get well.

As doctors we are generally encourage to practise evidence-based medicine (EBM). My experience is that doctors tend to take this to mean medicine which 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 (see here). 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’ [2].

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 Professor Whorwell has not, seemingly, taken this path, and is still acutely aware of the importance of listening to his patients. (See here for an example of what can happen when health professionals don’t extend this courtesy to their patients).


1. Whorwell PJ. The problem of insoluble fibre in irritable bowel syndrome
BMJ 2009;338:a3149, doi: 10.1136/bmj.a3149

2. Sackett DL, et al. Evidence based medicine: what it is and what it isn’t. BMJ 1996;312:71-72

One Response to BMJ letter reminds doctors of limitations of science and the importance of clinical experience

  1. Hilda Glickman 17 January 2009 at 2:44 pm #

    This is avery interesting article. So often medics will poo poo the clinical evidence that nutritionists have in taking people off wheat with dramatic results. One client of mine had digestive problems for 41 years and they cleared up after wheat was eliminated. See the book by Braly called ‘Dangerous Grains’ which gives a good explantion of why grains can affect the digestice system so badly.

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