Author: Giulia Enders


The driver for this book is the author’s concern that the public is largely unaware of the functions carried out by the gut beyond its role in digestion. Attributing this situation to the reticence of scientists to publicise their ‘important research results’, preferring to ‘bury’ the information in academic journals, the author set out to impress on ‘a broad audience’ the multifaceted contributions of the gut, especially to the immune and the nervous systems. In the process, the author provided countless surprising details about the structure and function of the gut which bely its underrated perception as just a digestive tube. The author also reviewed several disorders of the digestive system along with providing practical guidelines on their prevention. The book is also a self-help resource on how best to maintain a healthy alimentary system. The author’s pragmatic approach helps to strip away the awkwardness that otherwise hampers public discourse on gut-related themes which may be considered rather delicate (pages 3-4).

By DBCLS 統合TV, CC BY 4.0, Link


Perhaps as expected, the theme of bowel motions had a central place in the book, being the function that singularly symbolises the gut. The author addressed such subjects as the frequency and consistency of bowel evacuations with candour and directness, demonstrating an appreciation that these are topics that are sources of concern and misunderstanding for many. For example, in discussing constipation, the author reassured that it is ‘not how often you need to go to the toilet, but how difficult it is’ that matters, and she made several suggestions on how to ‘get things moving in the bowel department’. She also explored bowel-related matters that may not occur to many people, for example when she pointed out that adopting the wrong posture when emptying the bowels may put ‘too much pressure on the end of the gut’, with the attendant risks of haemorrhoids and diverticulitis. In this regard, she recommended squatting as ‘the natural pooping position for humans since time immemorial’ because it enables faster and more complete bowel emptying. Equally enlightening were the author’s discussion of faecal matter which depicted healthy faeces as consisting of three-quarters water, and is brown to yellowish-brown in colour. She also referred to the Bristol stool scale which grades stool consistency into seven groups, only a couple of which are healthy (pages 102-113, 14-15, and 64-69). 

Toilet sign. Leo Reynolds on Flickr.

The astonishing degree to which the gut is colonised by microbes formed a major theme of the book, the author exploring the usually beneficial effects of this but also highlighting its potential for harm. To convey a sense of the magnitude of this microbial colonisation, the author pointed out that microorganisms constitute 90% of the cells in the human body, and 90% of these reside in the gut. She emphasised the scale of this occupation when she noted that there are 100 trillion bacteria in the gut, and they can together weigh up to two kilograms. As a reflection of the critical role gut bacteria perform in bodily health, the author cited scientists who consider the gut microbiome to constitute an organ all by itself, carrying out essential metabolic and immune functions. She stressed their importance further when she remarked that ‘when something is wrong with our microbiome, something goes wrong with us’. She highlighted specific gut microbes such as Helicobacter pylori, a bacterium she characterised as ‘one of humankind’s oldest pets’ because it has colonised humans for more than 50,000 years. She added that whilst H.pylori confers protection against diseases such as asthma and eczema, it also increases the risk of diseases such as stomach ulcers and Parkinson’s disease (pages 136-147 and 182-208).

Helicobacter pylori. Penn State.

The intricate interaction of the gut and the brain epitomises the less well-appreciated features the the digestive system. The book explored this theme with reference to the gut’s extensive enteric nervous system which the author depicted as ‘just as large and chemically complex as the grey matter in our heads’. She pointed out that this structure, acting almost autonomously, has a feedback system via the vagus nerve through which it enables the gut to wield significant control over the brain. By this arrangement, the gut sends invaluable information to the brain to affect our behaviour, for example by affecting our emotions and motivations. The gut also contributes to our decision-making through the gut instincts it evokes in the brain, and it helps to create our sense of self-awareness through the signals it sends to the insular cortex. The author explained that the gut has such a privileged deterministic effect because, unlike the brain which is ‘heavily insulated and protected‘, the enteric nervous system is ‘right in the thick of it’ – fully aware of ‘how the body is doing’ at all times (pages 116, 74, 116-125, 131-132 and 248-258).

CC BY-SA 4.0, Link

The book’s assessment of the pathologies that compromise the gut was as important as its exploration of the gut’s normal functions. Amongst the more conventional impairments the author examined was irritable bowel syndrome, a disorder which she attributed to ‘activity in the emotional centre of the brain normally associated with unpleasant feelings‘. The rarer syndromes the book discussed included fructose intolerance, a disorder arising from the deficiency of GLUT-5 transporters in the gut wall, and Roemheld syndrome, a phenomenon which arises ‘when so much gas collects in the stomach that it presses against the heart and vagus nerve‘ thus causing symptoms such as anxiety, breathlessness, and chest pain. Of practical relevance is the book’s review of the infections that emerge when the gut’s defensive function, accounting for two-thirds of the body’s immune system, is compromised by such factors as the inappropriate use of antibiotics. To boost the gut’s bacterial defences, the author advocated the use of probiotics and prebiotics, and to revamp it when impaired, she referred to such novel treatments as faecal bacteriotherapy or stool transplantation (pages 52-59, 123, 32, 3, 218-245 ).

Beneficial gur bacteria. NIH Image Gallery on Flickr.

Greatly enhancing the book’s appeal are the fascinating facts about the gut which it contains. For example, the author stated that ‘the surface area of our digestive system is about one hundred times greater than the area of our skin’; that ’95 per cent of the serotonin we produce is manufactured in the cells of our gut’; and that ‘people who never need to break wind are starving their gut bacteria and are not good hosts for their microbe guests’. Equally compelling are the facts that saliva contains opiorphin, an analgesic that is more potent than morphine; that tonsillectomy before the age of seven increases the risk of obesity and weakens the immune system’; and that the appendix is ‘made almost entirely of immune tissue’ and is ‘a storehouse of all the best, most helpful bacteria’. Many of the facts the author highlighted had the potential to remodel human behaviour, for example when she said burping is easier when lying on the left side; ‘alcohol can multiply the number of gas-producing bacteria by a factor of up to a thousand’; and cigarette smoking causes reflux and heartburn because it ‘tricks the brain into producing more gastric acid for no practical reason’ (pages 30-41, 86-88, 130, 240 and 21-27).

By Leonardo Aguiar from São Paulo, Brazil – Intestines, CC BY 2.0,


This book throws a light on a relatively overlooked body organ, and it succeeds by employing a refreshing matter-of-fact approach. The book not only details the normal anatomy and physiology of the digestive system, it also highlights the factors that can impair these. With a light-hearted and conversational prose, the author conveyed important insights about the alimentary system that go far beyond its recognised digestive functions. There was perhaps a disproportionate emphasis on the minutiae of the microbiome which bordered on the academic. The illustrations also did little to enhance the books contents. Some of the author’s assertions were also not supported by robust research evidence. The coverage of the book is however comprehensive, and the recommendations it makes are helpful and timely.

Overall assessment

This book addresses a rather underestimated and disregarded organ which nevertheless performs many critical functions. The book stresses the importance of the gut’s nutritional role whilst pointing out its crucial defensive function. Perhaps most insightful is the authors exploration of the role the gut plays on mood, behaviour, and decision-making. The book therefore underscores the primacy of nurturing a healthy gut with recommendations that have both preventative and therapeutic implications. The book is directly relevant to the personal and professional lives of doctors and their patients, and I recommend it.

Book details

Publisher, Place, Year: Scribe Publications, London, 2014
Number of chapters: 3
Number of pages: 279
ISBN: 978-1-911344-77-3
Star rating: 4
Price: £9.75

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