Let’s Talk About Poo – 2


It’s been two years and nine months since I wrote Let’s Talk About Poo. This week I have found myself considering the problem of childhood constipation, and looking back at what I wrote then, I realise that I am more or less saying the same thing all over again – just perhaps in a bit more detail this time.

It began with a CbD. For anyone outside the medical profession this stands for Case-based Discussion: a formative workplace-based assessment designed (as one part of a comprehensive assessment strategy) to ensure doctors’ competence and fitness to practice, and to reassure the general public that they are safe in our hands. I have to do 12-20 per training year.

For reasons of confidentiality, I can’t give any details of the original case I discussed with my consultant colleague. Suffice it to say that it was a case of severe constipation. I questioned whether a dietary approach to treatment may be beneficial, and was advised in my feedback to read about the relationship between diet and constipation.

So I did a literature search (all the databases on the NHS Evidence website). I was looking primarily for dietary intervention studies in paediatric patients (all designs and any quality), but also for review articles and other studies that might yield further results on examination of their references. I used the search terms constipation AND diet AND child*. It returned 496 results. So far I have examined the first 100 (this is an ongoing project, and I will add updates), from which I selected eight for full text review.

One was an interventional prospective study of consecutive cases administered two tablespoons of green banana for eight weeks (resulting in reduced laxative use and reduced abdominal pain). One looked at a combined intervention of transcutaneous electrical stimulation (TES), disimpaction, laxatives and diet modification (resulting in greater and more rapid improvement than TES alone). One was a prospective, randomised study to assess the differences in compliance to a high fibre, high water diet following either physician advice or personalised dietary management by a registered dietician (resulting in better compliance with the personalised plan). The others included a prospective cohort study assessing the relationship between diet and later development of constipation (showing that a ‘Western-like’ dietary pattern was associated with a higher prevalence of constipation up to 48 months, as compared to a “health-conscious” pattern), and three review articles.

Because I’m at risk of going on about this forever, and I’m conscious that the optimum word count for blog posts is about 500, I’m just going to focus on one study for now, that I found particularly interesting…

 

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Chronic constipation in children: can it be managed by diet alone?

Karen Olness and John Tobin. Postgraduate Medicine Vol 72, No. 4: Oct 1982

60 children (37 boys and 23 girls) aged 2 to 12 years with chronic constipation with or without soiling who presented consecutively over a three year period to a single centre in Minneapolis, USA, were treated with an empirically formulated six week dietary intervention comprising raw bran (3 heaped teaspoons <6 years; 4 heaped teaspoons >6 years) and the exclusion of dairy products, bananas, apples and apple juice, carrots, rice and gelatin. Wholegrain bread and cereals were recommended and children were encouraged to eat salads and all fruits except apples and bananas.

They noted that “the families and referring physicians of 41 of the patients had initiated numerous treatment regimens, but none had included a rigorous dietary approach”. 25 patients had a history of constipation from birth or for more than five years. 18 had been referred for biofeedback for soiling. Spinal dysraphism, hypothyroidism, Hirschprung’s disease and severe emotional disturbances were excluded. The diagnosis of constipation was made by history, examination (including PR exam) and plain abdominal x-ray. Laxatives were stopped during the study period, although bisacodyl enemas were given for initial faecal impaction and at any time if defaecation did not occur within a 48 hour period. Patients kept a diary of all bowel movements.

In 1976 a comparative study suggested that raw bran may be more effective at reducing bowel transit time that cooked bran (1). In this study the bran was mixed with peanut butter and jelly, or added to soup, breakfast cereal or (if these were rejected) other cooked foods such as “hamburgers, pancakes, casseroles”. At the end of the trial period excluded foods were reintroduced but patients were advised to continue to take bran.

The authors reported that constipation was resolved by diet in all 60 children in this study within an average of 4.3 weeks. They defined resolution as passing soft, normal-sized stools that passed easily at 24-48 hour intervals. Follow up was for 24 months by telephone: seven patients continued to experience soiling and were referred on for biofeedback; six patients discontinued the diet completely and [some or all of these?] required enemas following recurrence of symptoms.

The authors acknowledged that this was not a controlled study (and also that “it would be difficult to design a double-blind, diet-controlled study of constipated children“), and that it was not possible to identify exactly which dietary components were responsible for the observed effects in each individual child. Nevertheless, the results are supportive of a role for dietary manipulation of some sort in the first line treatment of chronic constipation.

And as always, more research is needed. This study was carried out in 1982, and to date, it doesn’t appear that anyone has attempted to repeat it, or anything similar, using at the very least a randomised controlled (dietary intervention vs. normal care) study design and sufficient numbers to achieve adequate power.

 

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My curriculum states that I need to be familiar with, and able to follow, local and national guidelines for the management of constipation. The relevant national guidelines are the NICE Guidelines on constipation in children and young people [CG99, May 2010]. They recommend that dietary interventions are not used alone as first-line treatment for idiopathic constipation. Instead they recommend laxatives in combination with behavioural interventions and dietary modifications to ensure that a balanced diet and sufficient fluids are consumed. They state that a balanced diet should include an adequate intake of fibre from foods such as fruit, vegetables, high-fibre bread, baked beans and wholegrain breakfast cereals, but advise not recommending unprocessed bran, as this can “cause bloating and flatulence and reduce the absorption of micronutrients”. A cow’s milk exclusion diet should only be started on the advice of the relevant specialist services.

It may be noteworthy that Dr David Gillen, Medical Director at Pfizer (manufacturers of FiberCon) was one of the five members of the Guideline Review Panel. NICE states that:

The Guideline Review Panel is an independent panel that oversees the development of the guideline and takes responsibility for monitoring adherence to NICE guideline development processes. In particular, the panel ensures that stakeholder comments have been adequately considered and responded to. The panel includes members from the following perspectives: primary care, secondary care, lay, public health and industry.”

It should be remembered, in interpreting any NICE guideline therefore, that the recommendations are not based purely on the available scientific evidence, but also on the opinions and interests of stakeholders, including the pharmaceutical industry.

20 studies were identified for inclusion in the review, from 1022 citations initially highlighted by the search strategy: one triple-blind RCT, six double-blind RCTs, three open-label RCTs, two open label non-RCTs and eight prospective case series (two with an embedded food tolerance challenge test).

Of these, five examined specific formula milks, three examined probiotics, one examined increasing fluid intake and one examined increasing physical activity (in children with quadriplegic cerebral palsy). Five examined fibre supplements (2 x glucomannan B capsules, prune and fig concentrate, cocoa husk sachets mixed with milk, fibre-enriched yoghurt drinks). Four examined the effect of cow’s milk exclusion (more on this later). Only one examined the effect of modifying the diet with food: Kellogs All-Bran was added to the breakfasts of 20 severely developmentally disabled children (hardly generalisable to our ambulatory population) in a residential institution in Hong Kong, resulting in a significant decrease in laxative use.

From this the guideline concludes that: “there is no evidence for the clinical effectiveness of dried or fresh fruits, fruit juices, vegetables, cereals, fructo-oligosaccarides, omega 3 fish oils or excluding goats‘ milk from the diet for ongoing treatment or maintenance in children with chronic idiopathic constipation.”

A more accurate wording of this statement might read: “no randomised controlled trials have to date been carried out to assess the clinical effectiveness of dried or fresh fruits, fruit juices, vegetables, cereals, fructo-oligosaccarides, omega 3 fish oils or excluding goats‘ milk from the diet for ongoing treatment or maintenance in children with chronic idiopathic constipation.”

N.B. “THERE IS NO EVIDENCE”, MEANING “NO HIGH QUALITY STUDIES HAVE BEEN DONE”, IS A COMPLETELY DIFFERENT KETTLE OF FISH FROM “THERE IS NO EVIDENCE” MEANING “LOTS OF LARGE, WELL DESIGNED STUDIES HAVE BEEN DONE AND SHOWN NO EFFECT”…

The authors might also have reasonably noted that it is not possible to conduct a randomised, placebo-controlled, blinded trial of any whole-food dietary intervention, and that therefore this methodology is not appropriate for the assessment of the efficacy of such treatment options. It is likely that the search strategy and inclusion criteria used by the guideline development team will have missed much valuable information on the subject amongst the 1002 rejected citations. Whether or not this was deliberate (they set their search criteria at a level that ensured no evidence would be found), or entirely unwitting, I will leave up to you to decide. But I will end by noting that assessing the relationships between diet and any kind of disease requires the triangulation of various forms of evidence (interventional studies, case-control and cohort studies, ecological data relating to populations). Only when all the studies seem to be pointing in the same direction can we begin to draw valid conclusions.

 

References:

1. The effect on intestinal transit and the feces of raw and cooked bran in different doses. Wyman JB et al. Am J Clin Nutr 1976;29(12):1474-9

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