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It's remarkable how often patients will describe their bowel habits to me as being 'normal' – as if they've conducted a thorough investigation into the bowel habits of a large and random sample of people of both sexes and all ages and found themselves to be situated comfortably within the mid-range. In truth, there is a very wide range of bowel habits among the general population, which means that at least some aspects of almost anyone's bowel habit could be described as normal.
In fact, what most people mean by describing their bowel habits as normal is generally quite straightforward: as far as the average person is concerned, normal means having one bowel action every day.
There are people who believe that going more than once a day is a sign of exceptional normality, and regard such frequency as a desirable, even noble goal. There are others who think that regularity – having that all-important daily bowel action at the same time every day – is also normal, proudly announcing that they could 'set their clock' by the workings of their bowel, and feeling pleased and even righteous as a result. Others, still, attribute normality to bowel actions that float rather than sink; for these individuals, the relative buoyancy of their output appears to hold particular significance.
But by and large, most people are more or less of the opinion that 'normal' means 'daily'. However, while I can confirm that a daily bowel action is indeed approximately average for the human population as a whole (and I personally have conducted an investigation into the bowel functions of a large and random sample of people of both genders and all ages), this view of normality fails to acknowledge the wide range of variations that exist among us and – even worse – fails to recognise that a daily bowel action does not necessarily equate to a satisfactory bowel habit.
'Normal' versus satisfactory
Assessing the adequacy of a bowel habit on the basis of stool frequency alone completely ignores a whole range of factors that turn out to be vastly more important in determining whether we experience a truly satisfying bowel action or have a genuinely satisfactory bowel habit. And, as for regularity and buoyancy, these are of even less significance.
So what makes a bowel action 'satisfactory'? As it turns out, there are four key characteristics, which we'll take a look at now.
The four key characteristics of a satisfactory bowel action
In all of recorded human history, every truly satisfactory bowel action has had four things in common: it has been prompt, effortless, brief and complete. Wherever and by whomever it might have been produced, any human bowel action that has possessed all four of these characteristics will have represented a genuinely positive life experience for that person. And any individual who can say that they achieve such agreeable bowel actions on a majority of their visits to the bathroom can rightly claim to have a good bowel habit.
You need only ask yourself: 'Do I regularly commence rectal evacuation with a minimum of delay? Does it involve a minimum of effort? Am I regularly able to leave the bathroom after just a short period of time? And do I leave feeling satisfyingly empty?' If the answer to all of these questions is 'Yes', then you have an excellent bowel habit. If it's not, then you are likely to be struggling.
Notice that what does not count here – or, at least, not to anywhere near the same extent – is stool frequency, or how many times a day or a week you empty your bowel. This is an extremely important point: How often you go is simply not as important as how easily and how completely you empty your bowel.
People who are having difficulty with their bowels – those who are not able to experience the simple but significant pleasure of having regularly satisfactory bowel actions – can almost always describe their difficulty with reference to one or more of these four characteristics. They might experience delay with the initiation of bowel actions, difficulty getting bowel actions to pass, lengthy periods of time in the bathroom or an inability to completely empty their bowel. While many different factors and conditions can cause trouble with our bowels, they virtually all manifest as problems in one or more of these four key areas.
Throughout the course of this book you will see how these four potential sources of bowel trouble – initiation, effort, duration and completion – are all interrelated, and how difficulties in one area can often result in difficulties in the others. Before we move on, however, let's get out of the way two far less important characteristics that people are often (needlessly) concerned about.
What about odour and buoyancy?
Odour and buoyancy are two qualities of the output of our bowels that we all notice and perhaps sometimes wonder about but rarely discuss, so they are each worthy of brief discussion here.
Is it supposed to smell bad?
Odour is part and parcel of bowel function. Both the solid and the gaseous outputs of our bowels smell and, by common consensus, both of these smells are offensive – all the more so when they have been produced by someone else.
Given that we all eat food, and that most foods when left outside to rot will acquire an offensive odour, it shouldn't be too surprising that exactly those same sorts of foods, when mixed together and kept inside us at body temperature for 24 hours or more, will end up smelling bad. Add to this the smells associated with the gases produced by the action of the bacteria living in our bowels (more on this later), and there are good grounds for the output of our bowels to have an offensive odour.
Interestingly, the gases we produce in the largest quantities – hydrogen, carbon dioxide, methane, oxygen and nitrogen – are odourless. Much of this gas is derived from swallowed air and not necessarily from bacterial action in the bowel. This explains why the gas we produce is not always offensive and is, occasionally, entirely odourless. It is the sulphur-containing gases that primarily account for the offensive odour. The main gas in this group is hydrogen sulphide; others include methanethiol and dimethyl sulphide. Which particular foods contribute to the production of each specific gas is not, however, quite so clearly understood.
In fact, there is much that we do not yet know about the precise composition of the gases that emanate from our bowels. Recently there has been increased interest in the significance of the bacterial population of the human bowel, and how variations in this balance can affect our health. Even the fantastic notion of 'transplanting' some of the bowel contents of one person into another to substantially alter that person's bacterial population has assumed a level of credibility within medical circles (more on this in Chapter 7).
What remains an established fact, however, is that the odour of our bowel products, however putrid, really doesn't matter much at all. Over the years, many of my patients have complained to me about the intensely offensive odour of their own gas (or that of their partner); I have never yet been able to associate a single instance of this particular presenting complaint with any specific illness.
It is true that certain diseases are associated with particularly smelly bowel output – including malabsorption syndromes such as lactose intolerance or fat malabsorption, and conditions that result in bleeding into the intestinal tract – but people with these diseases invariably complain of the symptoms of the underlying disease first and foremost. For these people, other symptoms predominate and the foul odour is secondary. For those whose complaint primarily focuses on the smell of their output, my experience has been that there is rarely if ever anything about which to be concerned.
Is it supposed to float?
As for buoyancy, here is the ultimate expression of an individual's conceit at the superiority of their own particular produce. Somewhere, sometime, someone noted with awe and pride that their stool was formed and floating, defiantly refusing to disappear discreetly down the S-bend, insisting on being noticed and admired in all its perfection of contour and colour. And when this was repeated on more than one occasion – and since such a well-formed stool was likely to have been complete, resulting in a comfortably empty feeling – its satisfied creator will have concluded that it was the floating that mattered most.
It seems almost certain that this was a man. Men often take close note of their bowel actions – probably looking out for that perfectly formed example of the species. Occasionally they will produce one in a public toilet and not even attempt to flush it away, imbued with the belief that others should be given the opportunity to view and admire this outstanding specimen. Other bulky and unusually buoyant bowel products simply defy every effort to flush them away, steadfastly floating on until time and erosion reduce them to ordinariness.
At the risk of deflating the pride of those self-congratulatory individuals described above, the buoyancy of any individual stool will be determined simply by its density. Certain specimens entrap gas within them and so tend to float. Others include little entrapped gas and so tend to sink. As noted above – and as we discuss in detail throughout this book – what matters in a bowel action is that it should be prompt, effortless, brief and complete. Whatever you subsequently see or do not see floating in the toilet bowl is irrelevant.
By all means, pursue a diet that helps you to achieve a formed stool (as we discuss later, consistency itself is important) and encourages the four characteristics outlined above. But do not pursue a diet specifically in search of a floating stool (or a sinker, for that matter). It matters not one jot whether our output sinks or floats, twirls, bobbles or corkscrews, rotating clockwise or counter. The output of a bowel action that is prompt, effortless, brief and complete is a good thing, whatever it subsequently does upon striking water.
Having cleared that up, let's get to know how the bowel actually works.
How the bowel works
Our first step towards understanding how the bowel works is to understand the basic anatomy of a bowel action.
Anatomy of a bowel action
As Figure 1 illustrates, the small intestine starts where the stomach ends, and continues until the large intestine begins at the terminal ileum. (Note, in medical terminology, the terms intestine and bowel are interchangeable, so that small intestine is also known as the small bowel, and the large intestine also as the large bowel. However, throughout this book, for the sake of simplicity, we use the terms 'small intestine' and 'large intestine', the latter of which is synonymous with the everyday term 'bowel'.)
The large intestine comprises (in order) the colon, the rectum and the anus (also called the anal canal). The colon comprises (in order) the caecum (pronounced SEE-kum), the ascending colon, the transverse colon, the descending colon and the sigmoid colon.
The contents of the large intestine is called faeces (pronounced FEE-seas). The faeces that we pass out during a bowel action is referred to as a stool. The gas that we pass out is called flatus (pronounced FLAY-tus). What we eat generally takes about 24 hours to be expelled out the other end, but the pace of this journey varies at different stages. A comprehensive discussion of the entire process by which the food that enters our mouth comes to exit our body via the anal canal is beyond the scope of this brief book, so we'll start somewhere in the middle of that journey. Suffice it to say that the food we consume has already been chewed, swallowed, moistened and churned by the time it enters our small intestine.
The passage of food through our small intestine is very rapid. It is propelled by a series of powerful peristaltic (wave-like) muscle contractions through the entire length of the small intestine – during which time it is also being digested and its nutrients absorbed – and is dumped (now mostly in liquid form) into the caecum, the first part of the large intestine. The time it takes our food to get from our mouth to our colon is relatively short: three hours or less after a meal, virtually all of the food eaten at that meal has already entered the colon. At this point, however, things slow down considerably.
Our colon is a much more relaxed organ than the small intestine, happy for its contents to be stored for hours or even longer, until muscle contractions of generally only mild to moderate strength arise and move these contents (now called faeces) along its length. Propulsion through the colon occurs as a result of muscle-contraction waves referred to as 'mass movements'. These are provoked by a range of factors, which we'll look at in a moment. They occur with variable frequency and variable intensity among the human population. In some people these contraction waves are able to propel the entire contents of the bowel from caecum to rectum and out of the anus in one sitting, while in others they're often unable to nudge the faeces even a few centimetres.
Overall, however, a mass movement tends to propel faeces part but not all of the way around the large intestine. So the food you ate three hours ago for lunch might now be sitting in your caecum, a mass movement having moved what had previously been in your caecum (perhaps from breakfast this morning) around to your transverse colon or beyond. The next mass movement you experience will serve to propel your lunch from caecum to transverse colon and your breakfast from transverse colon down into your rectum, where it will demand to be expelled.
Colonic transit time
The time it takes for faeces to be moved through the entire large intestine – from when it first enters the caecum to when it is expelled through the anus in the course of a bowel action – is referred to as the colonic transit time.
As noted above, while the transit of food through the small intestine is predictably brisk, colonic transit time is generally slow. Any variation in how frequently different people open their bowels is thus much more likely to reflect variation in colonic transit time than differences in the speed of passage through the small intestine.
In other words, the time it takes the food we eat to be expelled from our bowels is primarily influenced by the colonic transit time and much less so by the generally fast and predictable transit through stomach and small intestine.
Numerous factors provoke the mass movements that propel faeces around the large intestine and so determine colonic transit time. These include the entry of food into the stomach upon eating (the so-called gastro-colic reflex); the entry of digested food from the small intestine into the caecum; specific chemicals in foods that stimulate these muscle contractions; physical exercise; and the simple act of getting up and out of bed. In many people, these factors aggregate each morning (getting up, eating breakfast, drinking a hot cup of coffee), which explains the most common human pattern of a daily bowel action in the morning.
Other factors that commonly influence our colonic transit time include what we eat (fruit, vegetables, caffeine, spicy foods and alcoholic drinks commonly speed things up); how much we eat (small-volume weight-loss diets often aggravate constipation); how much we exercise (a brisk walk can often provoke a strong urge); medications we are taking (a short list of commonly used medications that can cause trouble in either direction is provided in Chapter 6); and emotional stress, which tends to make whichever tendency we have – whether towards constipation or urgency – more marked.
But perhaps the most important factor influencing colonic transit time in humans is totally beyond our control – our sex. As it turns out, men and women have, on average, very different colonic transit times and, as a consequence, very different bowel habits and clinical presentations.
Mars and Venus in the bathroom
In a simple but compelling study performed at the University of Minnesota more than 30 years ago, the bowel habits of healthy adult men and women were compared. During the study, all the participants consumed identical amounts and types of food and drink, and the frequency of their bowel actions, the total weight of stool produced and even the volume of flatus expelled were measured. The study found that, on average, the men opened their bowels more often and produced a greater weight of stool and a greater volume of flatus than did the women.
Excerpted from "The Happy Bowel"
Copyright © 2018 Michael Levitt.
Excerpted by permission of Fremantle Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
Chapter 1 What's normal?,
Chapter 2 How the bowel works,
Chapter 3 Getting the process started: how do we know when it's time to go?,
Chapter 4 Completing the process: the importance of being empty,
Chapter 5 The use of laxatives,
Chapter 6 Other medications that affect the bowel,
Chapter 7 Alternative treatments: faecal transplants, probiotics, enemas and colonic irrigation,
Chapter 8 The relationship between bowel and brain,
Chapter 9 Bowel problems in children,
Chapter 10 Case studies,
Chapter 11 Frequently asked questions,