The problem of insoluble fibre in irritable bowel syndrome
I was surprised to read in the popular press that, according to the
British Medical Journal, fibre is good for irritable bowel syndrome (IBS).
In 1994 we raised the possibility that, at least in the secondary
care setting, cereal fibre was actually more likely to do harm than good
in patients with IBS(1). Today, as a gastroenterologist who probably sees
more cases of severe IBS than the majority of my colleagues, I still find
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 these patients. In the body of their paper in the BMJ, Ford and
colleagues(2) acknowledge that as opposed to ispaghula (soluble fibre),
bran (insoluble fibre) is not effective in IBS but claim that the
possibility of an exacerbation of symptoms by bran is not borne out by
their findings, presumably because of the lack of side effects reported in
the trials they reviewed. However, it has to be remembered that trials of
fibre have traditionally looked for improvement or no improvement and do
not even allow for the possibility of deterioration because fibre is
considered a natural product that is 'harmless'. Indeed, for the same
reason any worsening of symptoms is likely to be attributed more to a
spontaneous exacerbation of the disorder rather than being regarded as a
side effect of the bran.
It seems reasonable to assume that the potentially harmful effects of
bran are going to be exaggerated in secondary and tertiary care because,
by definition, those individuals not made worse are less likely to be
amongst those who are referred in the first place. We have confirmed this
hypothesis by also studying the response to bran in primary care and
demonstrating that bran is less deleterious in this setting, although it
can still cause an exacerbation in some patients(3).
We live in times characterised by evidence based medicine and the
rapid dissemination of the results of research to the media. With respect
to the former, we must still listen to what our patients are telling us
especially when the question is subtly different to the question that has
been addressed by the evidence. With regard to the latter, we must be
extremely careful about the accuracy of what we write especially in the
abstract of a paper as this is not infrequently the only part that is
scanned by the busy reader. The concluding statement in the abstract of
the paper by Ford et al is misleading as it completely ignores the
substantial differences between soluble and insoluble fibre thus
encouraging some IBS sufferers to continue with a treatment, insoluble
fibre, which at best is doing them no good but at worst may be doing them
1. Francis CY, Whorwell PJ. Bran and irritable bowel syndrome: time
for reappraisal. Lancet 1994;344:39-40.
2. Ford AC, Talley NJ, Spiegel BMR, Foxx-Orenstein AE, Schiller L, Quigley
EMM, Moayyedi P. Effect of fibre, antispasmodics and peppermint oil in the
treatment of irritable bowel syndrome: systematic review of the literature
and meta-analysis. Btitish Medical Journal 2008;337;a2313.
3. Miller V, Lea R, Agrawal A, Whorwell PJ. Bran and irritable bowel
syndrome: the primary-care perspective. Dig Liver Dis 2006;38:737-40.
Competing interests: No competing interests