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Study Finds Dietary Fibre is More Likely to Cause Rather Than Cure Constipation

Published on March 14, 2013,

Dr Briffa has been taking a look at a new study examining the impact of dietary fibre on people with constipation. His concludes that fruits, vegetables and so-called ‘healthy wholegrains’ are more likely the cause rather than a cure. This is from Dr Briffa…

Dr Briffa Escape The Diet TrapI get a sense that almost all individuals feel better for having regular, easy, complete bowel motions. Should someone be having problems in this area, the usual first-line approach is to up the intake of fibre. This can come in the form of fruits and vegetables, but many will see ‘healthy wholegrains’ such as wholemeal bread and high bran breakfast cereals as good and convenient options. However, a recent study suggests that if overcoming a sluggish bowel is the aim, one of the last things we should be doing is upping our fibre intake.

The study focused on 63 adult (average age 47) individuals who had persistent constipation for which no medical cause could be identified. Stool (bowel motion) frequency was less than once every three days for at least three months. All participants were on a high-fibre diet and/or were taking fibre supplements.

Study participants were instructed to adopt a low-fibre diet, and specifically to eliminate fruit, vegetables, breakfast cereals, wholemeal bread and brown rice for two weeks. After this, participants were asked to continue eating as little fibre as possible if this helped their symptoms.

6 months after the start of the study, 41 patients had persisted with the ‘no-fibre’ diet, 16 were eating a reduced fibre diet, and 6 were on a high-fibre diet for a variety of reasons (including being vegetarian or religious reasons).

  • In the 41 patients on the no-fibre diet, average bowel frequency had increased from an average of once every 3.75 days to once every day.
  • In the 16 patients on the reduced-fibre diet, average bowel frequency had increased from an average of once every 4.19 days to once every 1.9 days.
  • In the 6 patients who remained on a high-fibre diet, bowel frequency was once a week initially, and it remained the same on the high-fibre diet (as expected).

Symptoms of bloating occurred in 0 and 31 per cent of the low- and reduced-fibre eaters respectively. Of those on the no-fibre diet, no one had to strain to pass a stool. Abdominal pain also improved in this group and any anal bleeding they had resolved completely.

The authors of this study start their discussion of these results with these words:

This study has confirmed that the previous strongly-held belief that the application of dietary fiber to help constipation is but a myth.

They then go on to attempt to explain their findings:

It is well known that increasing dietary fiber increases fecal bulk and volume. Therefore in patients where there is already difficulty in expelling large fecal boluses through the anal sphincter, it is illogical to actually expect that bigger or more feces will ameliorate this problem. More and bulkier fecal matter can only aggravate the difficulty by making the stools even bigger and bulkier. Several reviews and a meta-analysis had already shown that dietary fiber does not improve constipation in patients with irritable bowel diseases.

The authors also provide this handy analogy:

The role of dietary fiber in constipation is analogous to cars in traffic congestion. The only way to alleviate slow traffic would be to decrease the number of cars and to evacuate the remaining cars quickly. Should we add more cars, the congestion would only be worsened. Similarly, in patients with idiopathic constipation [constipation of no known cause] and a colon packed with feces, reduction in dietary fiber would reduce fecal bulk and volume and make evacuation of the smaller and thinner feces easier. Adding dietary fiber would only add to the bulk and volume and thus make evacuation even more difficult.

It’s difficult to argue with the logic of this, nor the results they achieved in their study subjects.

More (including study reference details) at:  Study finds dietary fibre is more likely to be cause of, rather than a cure for, constipation and other bowel symptoms

How a bread maker spreads misinformation about the nutritional value of its product

Published on October 16, 2012,

A fascinating article has appeared over at Dr Briffa looking at the all too cosy relationships between the food industry and some within science and medicine who seem happy to spin what is actually nothing more than propaganda on their behalf. He then details an example from the same day where a national bread company has achieved publicity from a highly biased account of the role of bread in the diet. Here’s an extract…

Pão / Bread

Warburtons Bread (Photo credit: Marcio Cabral de Moura)

Now, today, I read this story in the UK national daily The Express [more examples linked to below] which tells us how stupid we all are for thinking fibre can be found in foods like chocolate, eggs and beer, and bemoaning the fact that some us can go short on fibre if we eschew bread. Sound vaguely familiar? Well, you won’t be too surprised to learn that these nutritional nuggets have come from a survey conducted by, wait for it….Warburtons. On this occasion, it appears that the BNF [British Nutrition Foundation] has not been co-opted to help Warburtons sell its message, though GP (family physician) and TV doctor Dr Hilary Jones makes all the right noises with a general condemnation of low-carbohydrate diets.

The original industry paid-for pro-bread review seemed to me to provide a wholly biased account of the role of bread in the diet – a piece of balanced ‘science’ it most certainly was not (in my opinion). So, what about this latest salvo from Warburtons? Is fibre all that important, as is claimed?

The sort of fibre found plentifully in, say, wholemeal bread is known as ‘insoluble’ fibre – more colloquially referred to as ‘bran’ or ‘roughage’. This is said to provide bulk to our stools, and help prevent constipation and colon cancer.

Actually, insoluble fibre can irritate the gut, and provoke symptoms such as bloating and discomfort. On the other hand, the other main form of fibre – ‘soluble’ fibre – tends to improve bowel symptoms such as constipation and abdominal discomfort [1]. Soluble fibre is found abundantly in natural, non-processed foods such as fruits, vegetables, nuts and seeds.

The idea that insoluble fibre helps prevent colon cancer is often expressed, but is not supported by the research, either. For example, studies show supplementing the diet with fibre does not reduce the risk of cancerous tumours or pre-cancerous lesions [2-4].

The authors of a review on the role of fibre in lower bowel conditions including cancer concluded that “…there does not seem to be much use for fiber in colorectal diseases”, adding that their desire was to “emphasize that what we have all been made to believe about fiber needs a second look. We often choose to believe a lie, as a lie repeated often enough by enough people becomes accepted as the truth” [5].

More (including the relevant references) at: Bread makers Warburtons are again helping spread more misinformation about the nutritional value of its product 

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