Constipation: Myths and Misconceptions
In 2005, a group of senior gastroenterologists, writing in the American Journal of Gastroenterology, questioned a number of commonly held beliefs concerning the causes and treatment of chronic constipation. I was recently sent a copy of their paper by a colleague, causing me to useful to revisit their conclusions.
Auto-intoxication
This was the subject of a recent post in which I reviewed recent evidence that suggested that changes in the colonic microbiome associated with colonic stasis might produce or stimulate the release of chemicals that could cause effects in many parts of the body.
Dolichocolon
The authors suggested that there was no evidence to suggest that an elongated colon was necessarily the cause of or associated with longstanding constipation. If that is the case, then it begs the question, what is it associated with? I say this with some self interest because some years ago I underwent a virtual colonoscopy in a clinic in Harley Street while reviewing that procedure for The IBS Network. It demonstrated more diverticula that I had anticipated for a man in his fifties and an elongated colon. It is true, I didn’t suffer from constipation, but for many years I had enjoyed a very high fibre diet. So, I wonder if an elongated colon is not so much a cause of constipation but a result of the diet commonly used to treat it.
Fluctuations in sex hormones.
It surprised me that the authors concluded that menstrual fluctuations in sex hormones had a minimal role in altering gut function. Severe constipation during the reproductive years is much common in women compared with men and it is known that progesterone can delay transit time either experimentally or during the last trimester of pregnancy. The authors largely based their conclusion on a study conducted in just 18 ‘normal’ women. Although average colonic transit time was prolonged during the luteal (latter) phase of menstrual cycle and stool weight was lower, the results in this small sample did not achieve statistical significance.
Results may be different in patients with IBS. In a previous post, I quoted evidence suggesting that women with IBS suffer more painful menstruation and premenstrual symptoms than those without. Bloating and constipation are more common during the second half of the cycle in women with IBS, while abdominal pain, nausea and diarrhoea tend to increase just before a period and reach a crescendo on the first to second day of menstrual flow. They may also suffer from fatigue, backache, and insomnia during menstruation. Physiological recordings in women with IBS have shown that rectal sensitivity is exaggerated just before and during menstruation.
Hypothyroidism
Despite claims in medical textbooks that hypothyroidism (myxoedema) is a recognised cause of constipation, the authors could not find any reliable data on the prevalence of hypothyroidism in patients with severe constipation. One limited study, published 46 years ago, suggested that hypothyroidism may be associated with a reduced stool frequency while thyrotoxicosis may be associated with an increased stool frequency.
Fibre deficiency
For many years, it was assumed that a diet deficient in fibre was responsible for chronic constipation. Although there was little evidence to support that conclusion, there was abundant data to indicate that a diet rich in fibre can help to relieve constipation. Nevertheless, in a landmark study on IBS, Francis and Whorwell suggested that coarse wheat brain might make other symptoms, notably pain and bloating worse. Subsequent studies have questioned that conclusion. Currently, a high fibre diet is still regarded as first line treatment for constipation. Some constipated people may benefit from coarse wheat bran, though many gastroenterologists and nutritionists suggest that soluble fibre may be better tolerated by most.
Dehydration
As far as I can recall, the idea that dehydration and a low fluid intake could cause constipation was originally reported in a study from Australia where the climate is more extreme and dehydration more common. As the authors indicate, there is no evidence that constipation can successfully be treated by increasing fluid intake unless there is evidence of dehydration.
Inactivity
Many years ago, Dr Richard Asher, perhaps now better known as the father of the actress Jane Asher, wrote a paper on the dangers of going to bed in which he listed constipation as a consequence of prolonged bed rest. It is possible, however, that the difficulties of using a hospital bed pan may have had something to do with that.
I know of no definitive evidence that lack of physical activity is associated with constipation though I have frequently observed that long distance runners can suffer more from diarrhoea. This is so common that I have often referred to it as the running bowel in the running man. There is some evidence to suggest that Increasing physical activity as part of a broad rehabilitation program may benefit mild to moderate constipation, but other dietary and lifestyle factors may be as if not more important.
The dangers of senna.
To my recollection, it was a study conducted in mice in 1968 that first suggested that the laxative, senna many damage the enteric nervous system. Studies in humans on high doses of laxatives also showed axon degeneration, but this may have been due to an underlying neuropathy responsible for the constipation in the first place. Senna can cause pigmentation of the colon (melanosis coli), but this represents sloughed off epithelial cells and not nerve damage.
Discussion
This paper concludes that there is little evidence to support long held beliefs that bacterial toxins, an elongated colon, fibre deficiency, reproductive hormones, myxoedema, dehydration or inactivity cause constipation, nor that stimulant laxatives may make constipation worse by damaging or resetting the colonic nervous system. Nevertheless, examination of the data quoted suggests that most of these so called myths and misconceptions have not been entirely ruled out; it is just that the there is not sufficient evidence to support them. Many studies, especially with regard to the effect of the menstrual cycle, myxoedema either have insufficient statistical power to reach any conclusions or were not conducted in an appropriate context. More convincing results are obtained when studies were carried out in patients with IBS.
So many factors have been considered to be involved in causing constipation, yet epidemiological and clinical research have tended to focus on just one factor, while attempting to keep other possible factors constant. This is a very artificial situation. It is more likely that many different factors work in combination to culminate in constipation. For example, fibre deficiency may be more relevant in people who lack confidence or feel threatened or in those who have an abnormally long colon. Increases in methanogenic bacteria may cause the colon to be resistant to dietary fibre. Breakdown of steroid hormones by some species of colonic bacteria may mask the effect of the menstrual cycle. It therefore seems too early to dismiss some myths that have stood the test of time. Instead, they should perhaps be placed in abeyance awaiting more rigorous studies and better evidence.
Finally constipation is an individual illness, a unique combination of life situation and life style factors impacting on the microbial and neuro-chemical control of colonic function. What works for one person is not necessarily going to work for another.
If we take this paper at face value, then we might conclude there is no identified cause for constipation. That conclusion would, in my opinion, be false. There is one group of factors that have been excluded. Perhaps the authors would regard these as the greatest myths of all. They include the personality of the patient, their psychological history and the context.
In my last post on this blog, I outlined the notion that defaecation is a private act that requires sufficient time and confidence to complete. Any intrusion or pressure, any suspicion or lack of trust, will raise emotional tension and act via the sympathetic nervous system to inhibit colonic movement and faecal expulsion. Under those conditions, people may well be much more susceptible to hormonal or microbial factors that inhibit colonic motility and more resistant to dietary fibre and laxatives. A study on both personality factors and fibre intake conducted in a prison in the United States in 1981, showed that those individuals who displayed more self esteem and were more outgoing, tended to produce more frequent and heavier stools.
Ninety years ago, the psychoanalyst, Georg Groddeck, suggested a psychogenic origin to constipation. Since then many constipated patients have reported abolition of their constipation during psychotherapy and this has been accompanied by increases in stool frequency and reductions in stool frequency. Such individual reports are the stuff of anecdote and are difficult to validate by methods acceptable to clinical research, but they occur too frequently in psychotherapeutic practice to be dismissed as mythology.
The Sensitive Gut 