Study finds dietary fibre is more likely to be cause of, rather than a cure for, constipation and other bowel symptoms

I 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 adults (average age 47) individuals who had persistent constipation for which no medical cause could be identified [1]. 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.

And these results more-or-less mirror my own in practise. What I find tends to work well with individuals suffering from constipation and other ‘irritable bowel’-like symptoms is the elimination of grain, particularly wheat, from the diet. In practice, I’ve found leaving vegetables and some fruit (rich in ‘soluble’ fibre) in the diet allows individuals to attain and maintain good digestive function. My hunch is it’s the much-lauded ‘insoluble’ fibre in wholegrains that does the most damage, here. A review on the role of diet in managing irritable bowel syndrome concluded pretty much the same thing [2].


1. Ho KS, et al. Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms. World J Gastroenterol 2012;18(33):4593-4596

2. Heizer WD, et al. The role of diet in symptoms of irritable bowel syndrome in adults: a narrative review. J Am Diet Assoc. 2009;109(7):1204-14

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49 Responses to Study finds dietary fibre is more likely to be cause of, rather than a cure for, constipation and other bowel symptoms

  1. Chloe 5 March 2013 at 1:38 pm #

    WOW! It’s incredibly how little the establishment really knows about how our bodies work!

  2. Sandra 5 March 2013 at 1:59 pm #

    As usual the voice of sense and reason! So called healthy wholegrains gave me IBS type symptoms for years but cutting out wheat and eating a lacto paleo diet with plenty of soluble fibre has improved my digestive function no end.

  3. Richard Nikoley 5 March 2013 at 3:23 pm #


    A week or so ago I would have been quite skeptical, in spite of this being an intervention. But 8 days ago I had decided to try one of my self-experiements and went on a largely raw whole milk diet with kefir and kombucha mixed in (about 1,500 kcal per day, almost no hunger and great well being and energy). This would be a zero fiber diet (same as an infant would be on). No bowel issues. It was hugely diuretic and I dropped 5 pounds the first day, 1.5 the second, then .5 the third.

    Then, I reasoned that with all that probiotic I’m getting I maybe should feed the little buggers so I added a scoop of inulin / fructo-oligo-sacharide powder per day and 1/2 – 1 baked potato that had been cooled in the fridge overnight to form resistant starch.

    What happened? Constipation happened. I was stumped. Plus, I felt bloated, retained water, etc. I stopped the fiber and over the last couple of days, 6 pounds wooshed away. In all, 9.5 pounds dropped in 8 days but I suspect it could have been more.

  4. Keith 5 March 2013 at 3:23 pm #

    I am not a doctor, nor do I play one on TV, but I have a hypothetical question.

    A high fiber diet requires a fair amount of water to properly process & eliminate. If someone is eating large amounts of fiber, but not hydrating enough, this can lead to constipation. Been there, done that.

    If they then reduce their fiber intake (with no corresponding reduction in water intake) couldn’t that reduce symptoms of constipation?

  5. Paul 5 March 2013 at 3:34 pm #

    I do find it incredible that the medical profession should tell us to eat something (fibre) that we are completely incapable of digesting. It makes no sense whatsoever.

    I was ‘around’ when fibre, or roughage as it was then known, was first promoted as necessary for health. It is of course almost a uniquely British thing to worry about one’s bowel movements (if one was French, one would worry about one’s liver). The requirement to increase ‘roughage’ came about in the mid 1970s, and guess who was behind its promotion? Yes, breakfast cereal manufacturers. Presumably, these companies successfully lobbied the NHS to make sure that fibre became a necessary part of our diet under official guidelines.

    What really surprises me is that junk 1970s ‘science’ became part of received wisdom and hardly ever gets reviewed. I am not a doctor, so don’t know for sure, but I am pretty certain that medical students’ textbooks on nutrition will state that fibre is essential to health, and this is never questioned.

  6. Asclepius 5 March 2013 at 4:36 pm #

    I wonder if that traffic analogy could be extended to diabetics and carbohydrate?

  7. John 5 March 2013 at 4:40 pm #

    One fix for the high fiber diet and constipation – drink a lot of water. Dehydration impairs stool mobility.

    • Chris H 6 February 2014 at 6:41 pm #

      Not true! Potassium levels in the body control the water content of stools

  8. bert hubert 6 March 2013 at 6:17 am #

    The full paper can be found here:
    I do note that this result is from Singapore, and might not apply immediately beyond asians!
    Exciting nonetheless.

  9. Dr John Briffa 6 March 2013 at 11:22 am #


    If they then reduce their fiber intake (with no corresponding reduction in water intake) couldn’t that reduce symptoms of constipation?

    • Chris H 6 February 2014 at 6:40 pm #

      The water content of stools is not directly related to the amount of water consumed. Potassium levels determine their water content. If you drink too much water you will flush the potassium out of your body and have dry stools

  10. Jonathan Bagley 6 March 2013 at 2:16 pm #

    If this is true, who was originally responsible for the high fibre idea which virtually everyone has accepted throughout at least the last 50 years? I’ll wager it had something to do with John Kellogg, an advocate of vegetarianism who, with his brother, founded a breakfast cereal company. John also ran a sanitarium supplying colonic irrigation – presumably for the very small number of cases a high fibre diet couldn’t cure. According to WP, so may not be true, he was a eugenicist who worked on the rehabilitation of masturbators via circumcision. Glad our paths never crossed.

  11. Alexander Cranford 7 March 2013 at 8:59 am #

    This reminds me of the book Fiber Menace by Konstantin Monastyrsky. Allow me to quote form this page,
    “So if you believe that the introduction of fiber into the American diet came about as a result of thorough academic research, methodical clinical investigation, and penetrating peer reviews, I‘m sorry to disappoint you, but it didn‘t. It‘s actually based on profane sacrilege, fanatical misogynism, medieval prudishness, common quackery, crass commercialism, incomprehensible medical incompetence, and, by the legal standards of today, negligence and malpractice.”

    • Chris H 6 February 2014 at 6:44 pm #

      After suffering with GERD for 25 years and all medication has stopped working I followed Konstantin Monastyrsky zero fibre diet and with 5 days the GERD had gone. 4 months on and they never returned.

      Large amounts of fibre is not required by the human body. period.

  12. Fred Hahn 7 March 2013 at 7:55 pm #

    So….how come vegans aren’t exploding in the streets? I wonder what happens to someone who is on an all plant diet when it’s time to go. Must be ugly.

  13. Bernard 8 March 2013 at 8:28 am #

    I have found that taking plain fibre supllement (psyllium husks) and plenty of water does not help with constipation. The same supplement with some added herbs (Witch Hazel, Slippery Elm, Shavegrass, Liquorice root, Pumpkin seens, Irish Moss, Mullein Leaves, Marshmallow root, Devil’s claw, Capsicum, Black walnut, Plaintain, Alfalfa, Cascare, Oatsraw) worked admirably. Once stoppting treatment movements contuinued well as should be. Judging by the names of some of the herbs I little wonder why movement improved so much.

    • Ursula 11 April 2014 at 5:53 pm #

      Bernard, have you ever wondered if it wouldn’t have worked just as well (or better) without the psyllium husks?

  14. Liz 8 March 2013 at 8:50 am #

    Interesting. Is there a subset of people who do better on low fibre?

    I used to get horrible diarrhoea from wheat bran – I thought that was how the F Plan diet worked many years ago!!

    And I’m wondering what gave me constipation (and diverticulitis) when I went on the Atkins diet in a rather low fibre way some years ago?

    I find that a combination of a gluten free diet, psyllium husks with plenty of water, and probiotics help me avoid extremes in either direction

  15. Bernard 8 March 2013 at 9:29 am #

    Liz I find your comment interesting. When tested the test showed that I had no adverse reactioin to gluten. I tried a gluten free diet and I must say that bowel movements improived drastically as well as small aches and pains. There is a lot to be said for a gluten free diet, except for the cost of substitutes.

    • Ursula 11 April 2014 at 5:58 pm #

      The blood test for Celiac disease/gluten intolerance is so inaccurate it is nearly useless. It yields up to 50% false negatives, unless your bowels are so damaged that you’re near death.
      The only real valid way to test for gluten intolerance is to try eliminating it. If your symptoms subside, and then after about a month, when you try eating gluten again, you have an obvious reaction, you know you’re gluten intolerant.
      It seems you have done your own test, and are obviously gluten intolerant.
      But you would likely do even better if you’d skip the substitutes, as they aren’t just expensive, but unhealthy as well.

  16. Peggy 8 March 2013 at 9:39 am #

    As a sufferer of constipation from childhood I did find that a high fibre diet improved things hugely. However, in later years (I am 59) I found that my body has functioned better on rather less ‘hard core’ fibre (eg raw bran, etc).
    The problem with adopting a drastic reduction in dietary fibre is that as a vegetarian, much of my diet includes high fibre foods!!??

  17. kellie@foodtoglow 8 March 2013 at 9:55 am #

    As a cancer health educator I often see people with chronic constipation, pain and bloating, and after enquiring about their diet (and looking at their food diaries) we often agree that too much fibre may be an issue. They have been trying too hard to be healthy after their diagnosis. Most feel much better, and start having more comfortable bowel movements, by following a lower fibre diet for even just a few days. I do recommend that once the immediate symptoms clear that they gradually add back in fibre, trying to find their own personal balance with fibre and digestion. So glad you have covered this subject. People are always amazed that higher fibre isn’t for everyone.

  18. Jules 8 March 2013 at 11:16 am #

    The final paragraph in Dr Briffa’s article sums it up nicely for me. It’s the insoluble fibres (bread, cereals, pasta etc) that seem to be the problem, not the soluble (fruit, veg). The soluble fibre also has more natural water content anyway. I feel much better not eating bread, grains, pasta, cereals for a whole variety of reasons, but I still eat tons of fruit and veg ie. plenty fibre but of a type that suits me. I also have several vegetarian friends who eat a lot of bread and do not suffer from constipation, so perhaps lots of protein in the form of meat also slows things up, as Liza mentioned with reference to the Atkins. Do what’s right for you and your body.

  19. Georgia Ede MD 8 March 2013 at 12:03 pm #

    Hallelujah–research finally proves what common sense has been telling us all along–that an indigestible, abrasive, anti-nutritious substance is actually not good for digestion–imagine that:) Thank you for publicizing this important study. I agree with you, Dr. Briffa, that insoluble fiber (the woody stuff) is most likely the culprit, here. I personally was able to completely reverse severe IBS symptoms 5 years ago by switching to a low-fiber diet, so I’m just one example of a person who felt better by going against conventional medical advice.

  20. Megan 8 March 2013 at 1:21 pm #

    I have been aware of the controversy about fibre for years. A Greek friend of mine said that he had always upped his olive oil/fat consumption when so afflicted. He said it worked for egg-bound chickens too! Those researchers who spend long periods of time in Antarctica, for example, and who live only on meats of necessity do not suffer from chronic constipation. The body adjusts. This is my experience on a grain and sugar-free diet and on the grain-heavy, high fibre diet I no longer follow. It seems to suggest that a radical change in diet requires a digestive settling-in period. Could the beloved-of-medics low fat, high carb, high fibre mantra be another dated nonsense? Data exploding the myth that high fibre lowers cancer risk has been available for years.

  21. Kevin eakins 8 March 2013 at 2:56 pm #

    This study confirms my opinion that constipation is related more to dsybiosis than to any other single factor. My clinical experience indicates that dysbiosis and in particular the presence of parasites is a more critical in the causation of constipation than anything else. I agree that insoluble fibre is likely to be much more injurious than soluble. It would interesting to do this study again separating out the affects of soluble and insoluble fibre.

  22. John Walker 8 March 2013 at 3:30 pm #

    @Paul. I think you will find that in Germany there is a ‘fixation’ on bowel movements. Even the toilets are designed to make examination of stools easier. Inside the bowl there is a shelf placed in a strategic position. When I asked about this strange design, the hotelier told me that was what the shelf was for. So one can monitor one’s movements, which was taken seriously in Germany. I can only tell you what I was told. At the moment I have the opposite problem and I am hoping it’s just a touch of ‘Gyp’.

  23. Marly Harris 8 March 2013 at 4:38 pm #

    I was dubbed “Queen of Poops” on a zero-carb forum. After 60 healthy years as a vegetarian (13-73), I became a carnivore thanks to my increased access to scientific material (when I went online in 1998). Buying Monastyrsky’s book also let me know that I was not alone in my faith in a zero-fiber diet.

    So, the bowels were happy but I experienced muscle cramps in my legs, horrible painful spasms. I don’t take supplements but I thought perhaps magnesium would help.

    I’ve finally modified my all meat/fat/spices intake to include an avocado every day. Problem solved.

    My son was embarrassed seeing my comments online but making any subject taboo is ridiculous. Defecation should be a pleasant sensual non-event that is over quickly and odor-free. Our bodies are well designed when we don’t complicate things.

  24. William L. Wilson, M.D. 8 March 2013 at 10:45 pm #

    This blog post certainly reflects my experience. Since I started following a Paleo style diet with no grains, I have experienced great improvement in my bowel regularity. The whole grain/fiber story is a myth. You can get all the fiber you need from vegetables, fruits and nuts.

  25. George 9 March 2013 at 6:55 am #

    I have to say, Paul’s comment, published:

    5 March 2013 at 3:34 pm,

    is spot on..

    I myself am in disbelief at the scientific communities ignorance to 1900’s data on food.

    It should all be scrapped and re-reviewed / re-tested and re-examined.

    I can only assume there are people getting paid nice sums in official positions to either delay, or completely stop PROPER information from getting out.

  26. Alexander Cranford 10 March 2013 at 1:09 am #

    John Harvey Kellogg did not believe that even married people should have recreational sex, only for the purposes of procreation. Anita Roddick once said in a radio interview that “Stupidity is sustainable in America” . I have nearly but not quite as much contempt for breakfast cereal manufacturers as I do for margarine companies. Although not as unhealthy as margarine, nutrition-wise you get very little for your money. This money could be spent buying real food.

  27. Carol AKA CarbSaner 11 March 2013 at 8:35 am #

    John, I first read that fibre may be damaging from Barry Grove’s book ‘Trick and Treat’ – so many of the things I read there are now general knowledge ie about vitamin D deficiency, mammography etc etc etc.
    My mother-in-law was prescribed a high fibre diet a couple of years ago so she and my father-in-law started a ‘healthy diet’, mainly high fibre cereal. In a few months they both had rheumatoid arthritis.
    Personally fibre gives me awful abdominal pains. I found that taking a couple of small dose Vitamin D capsules works better.

  28. GiGi Eats Celebrities 12 March 2013 at 3:36 am #

    I hate that this is the truth and I have known it ALL along, yet I am in complete and utter denial because I adore my veggies – my only source of fiber intake. I suffer from severe stomach issues and I know fiber only makes it worse – especially because I eat a LOT of veggies to get my fiber quota. There is a happy medium range, but I always surpass it as veggies are my only source of carbohydrates as I cannot eat other sources. I do eat a lot of protein as well, and when I eat just protein at meals, I am completely fine, perfect in fact. I just cannot rid my diet completely of fiber, despite knowing this! :-/

  29. David 22 March 2013 at 11:43 am #


    I am a newbie on your blog; have your read T CLeave ‘The Saccarine Disease (1976)’, it’s on teh ‘net for free. In th navy, he ended up as the head of naval medical research, he was known as ‘Dr Bran’. In thae above piece he sasy that high fibre on its own will make minimal differnce to trasnit times and that bran is the addition required. But, and there is a big but, it is also a reduction in teh consumption of sugar and other refined carbohydrates that is the key.

    Not all carbohydrates are the same. as you nknow There is a world of differnce between polished rice and unhulled rice and even sugar (sucrose) and the whole cane. In the latter 100% of teh fibre and protein have been removed (90% of the plant). You can eat the latter and suffer no carries or well, pay your dentist!

    The diffential of qualities and impact of ‘carbs’ should be emphasised more clearly not that the BNF or Sugar Nutrition uk have any interest in that.

  30. André 29 March 2013 at 2:42 pm #

    I found that rye bread is a totally different story. In fact, it isn’t bread at all. Rye has soluble fibers that are not only probiotic, but water-binding as well. Fibers in wheat just don’t do that. And drinking lots of water flushes magnesium (and other electrolytes) from your system. And that makes matters worse. Magnesium is needed for the relaxation of muscles; even in your bowels. Knowing most people have a magnesium deficiency to begin with, advising lots of water is utterly senseless.

    I am in favour of low carb diets, but I allow rye bread on a daily basis as it solved all stool passing problems for me.

    Lastly, insoluble fiber itself may be the cause of bowel cancer, as the fibers are like little pins, scratching the inside of your bowels. Not good.

  31. Lisa 10 July 2013 at 2:31 pm #

    I have believed this for years since every time I have tried to increase fiber my constipation becomes much worse. Some try to tell me it’s just my body adjusting to the amount of fiber and it will eventually get used to it, but I ask how long must I suffer just to be regular? When I do not try to increase my fiber intake I typically have one large bowel movement a day. If I do increase it I may not have a BM for 2-4 days and it will be very large in size and usually causes anal fissures. This article makes me feel much better about following my bodies cues.

  32. Aly 25 September 2013 at 1:27 pm #

    What fruit and veg is safe? How many cups a day for a women smaller hight? Does it have to be cooked?
    I really needed this article. Been vegan (only produce, no grains at all) for 15 yrs! Constipation lead me to push so much so hard that my Bowel prolapsed and surgery increased the constipation worse than ever!
    I would only eat cow (or meats, eggs etc…) if it solves this problem!
    Any ideas to throw my way??

  33. Aly 22 November 2013 at 9:51 pm #

    If they weren’t eating fiber- what was the diet exactly?

  34. Aly 22 November 2013 at 10:04 pm #

    Lisa – what is your diet like?

  35. William L. Wilson, M.D. 22 November 2013 at 11:38 pm #

    A few years ago I eliminated most grains from my diet and most of my carbohydrates come from vegetables with some added fruit. Since I made these changes my bowels move like clockwork with no muss or fuss.

    I think we have now run out of reasons to recommend “whole grains” for any useful health purposes.

  36. Sean 24 November 2013 at 10:47 pm #

    I have been wheat and corn free for over 20 years – I grew up with bowel problems and developed arthritis at age 19.

    Best bowel days are SCD yoghurt with sunflower seeds, pumpkin seeds and sesame seeds.

    Too many carbs or baked stuff (I use rice flour) can still bung me up.

    Btw – arthritis is 75% better on my diet.


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