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It's amazing what your stomach actually does

I turn a magnifying glass on the stomach, chewing over the crucial role it plays in our health…and our happiness


While many of us might feel we’re ‘living in our heads’, the truth is we’re really a nation of navel gazers.

If there’s one part of the body, outside of the brain, which humans have long had a preoccupation for – it is the stomach.

So important was this gastric organ to the Ancient Egyptians, that they popped the stomachs of the dead into jars for safe transport to the after life – and since then the stomach has become the linchpin for a multitude of medical discoveries, influencing not only what we put in our mouths but even the thoughts that go through our heads.

If you want to woo your man, then it’s done through his stomach; if you’re fearful, you’ll get ‘butterflies in the stomach’, but if you’re brave, you might also be ‘gutsy’. And what of those gut instincts and reactions?


Belly basics

So what exactly does the stomach look like and what does it do?

As part of the gastrointestinal tract – which also includes the esophagus, small intestine, colon and rectum – our stretchy stomach is the first port of call for food.

“If you removed it from the body to look at, it would be a pale pink J-shaped bag,” says Dr Andrew Moore, consultant gastroenterologist at the Royal Liverpool University Hospital. “When it’s empty, it’s really quite small, with a capacity of less than 100ml, but in normal adults it can expand to hold at least 1litre of food and fluid – and, according to research, if inflated can take up to 8litres before popping.”

The biggest misconception about the stomach, says Dr Moore, is that it’s where all our food is digested. In fact, it’s only the first stage in the digestion process.

“The stomach in effect acts like a reservoir, allowing us to accommodate a proper meal,” says Dr Moore. “It helps us to gradually break down food so that the intestine can cope with it all, but it is in the intestine that food is broken down further and most of the absorption of nutrients happens.”

So what’s all the rumbling about? Stomach growls are in fact caused by tiny muscular contractions called ‘peristalsis’, which transport the food into the stomach and clench and release it until it forms a kind of slurry known as ‘chyme’.

“These contractions are primed to begin even before we’ve got the plate out of the cupboard,” says Dr Moore. “Because the stomach ‘anticipates’ the meal. It’s a fascinating process to watch through an endoscope!”

Intriguingly, these contractions don’t just happen when we’re hungry – they go on all the time, but when our stomachs are empty there’s more of an echo chamber.


Tummy troubles

While much of this may seem obvious to us today, if it wasn’t for one Dr William Beaumont, we may never have learned even these basic facts.

Known as the Father of Gastric Physiology, in the early 1800s he became the first doctor to see a living stomach after his patient, one Alexis St. Martin, suffered a shot to the stomach, which left a hole in the abdomen – and, consequently, a great view of the stomach.

“As the wound was incurable, Beaumont attached a fistula with a mental flap so that it could be lifted up and down and he see could inside, says Dr Ian Miller, Wellcome Trust research fellow in Medical Humanities at Ulster University. “In an era before X-ray technologies, this was a really important chance to look at an organ not normally seen, and he did lots of experiments (many of which would probably be considered unethical nowadays) to see what would happen when the patient ate different foods.”

While it can’t have been much fun for Alexis (apparently, he often got sick of being experimented upon and kept running off – only to be tracked down by Beaumont later), it was an important breakthrough.

Later on, German physician Adolf Kussmaul also developed the gastroscope – a lighted probe that was placed inside the digestive tract – by getting tips from a professional sword swallower on how to safely pass objects down the esophagus.


Acid house

If that’s not enough to give you tummy ache, then let’s revel in one of the most fascinating parts of the stomach’s activities – its gastric juices.

This corrosive cocktail of hydrochloric acid and pepsin – the first line of defence in the immune system that kills off problematic microbes – is produced at the rate of three litres a day by the stomach – and has the power to dissolve metal and bone.

So how come we don’t all have ulcers the size of dish plates?

The answer lies in the fact our stomachs are better at regenerating than the T-1000 Terminator, with the lining completely replaced every four days – but also in part because this lining is populated with cells called ‘epithelials’ that produces an alkaline, bicarbonate mucus, which protects the stomach.

Dr Moore, who was on the research team that first discovered the hormone that stimulates stomach acid, says a lot is blamed on the acid stomach.

“We once thought it was spicy or acid foods that caused ulcers, but perhaps the biggest breakthrough of the last few years has been the discovery of the Helicobacter pylori bacteria, which lives in a quarter of British stomachs and, in some people, causes sores and ulcers and stomach cancer,” he says.

This research certainly would have allayed the fears of the Victorians.

“Lots of anxieties about stomachs emerged in 19th century Britain,” says Dr Miller. “The industrial revolution and improved shipping technologies meant that the British now had access to curries and spicy foods, which provoked fears that the British were eating food their stomachs were not designed to digest.

“Some anti-alcohol advocates attempted to impress the negative effects of temperance on the audience attending their meetings by bringing along preserved, dissected stomachs…with one inflating the stomach and asking onlookers if they thought it was possible to put a pound of rump steaks and four pots of beer into such a small cupboard as that!”

Accordingly the Victorians produced a wealth of popular and medical literature on stomachs – perhaps the most memorable of these being an 1853 booklet entitled Memoirs of a Stomach, written by a remarkable literate stomach, named ‘Mr Stomach’.

“Many believed that industrialised, urban life had disrupted man’s natural eating schedule,” adds Dr Miller. “With the one exception to the rule being Manchester – a city whose communal practice of dining at one o’clock was indentified as particularly beneficial to health, prompting claims it should be introduce to every British town and city.”

Food for thought

Of course, our diet does have an impact on our stomach health – but the way we eat, is just as important as what we eat.

Chewing is a signal to the stomach to start sloshing that acid around, and it was Gladstone who claimed that he owed his vitality to thoroughly chewing every mouthful of food before it was swallowed (apparently training his eight children to give every mouthful thirty-two chews). Today, Chinese scientists have suggested 40 chews is the optimal for digestion (and weight loss) – but it’s all a bit tricky if you’re having soup or ice-cream.

“How many times have you eaten something and then don’t remember you have?” says Manchester-based nutritional therapist Helen Walker, who looks after the highly trained tums at FC United of Manchester in her role as club nutritionist. “If we don’t pay attention and be mindful when we are eating, it can disrupt the connection between the brain and the stomach, which helps us to judge when we’re getting fuller. And it also works the other way around when we are nervous, we don’t feel hungry as our stress response can reduce our ability to digest.”

Dr Moore agrees: “Food stimulates the nerves in the stomach and in turn the brain senses the stomach is distended and that tiny fragments of food are in the blood stream,” he says. “But this process can take up to 10-15 minutes, so if you keep eating in this window you can overeat.”

Indeed, if you thought your stomach was simply a food blender, think again.

“From around the 1790s, the stomach became viewed as ‘the great abdominal brain’,” says Dr Miller. “With John Abernethy, a prominent 19th-century doctor, blaming every single illness that his patients presented on bad diets and a bad stomach, from skin problems to tuberculosis and even insanity.”

And it’s not as far fetched as it sounds. Recent research has suggested a deep-rooted correlation between mental stress and the stomach, starting with the colony of microbes (or gut flora) – part of your body’s ‘microbiome’ – that produce neurotransmitters.

Sending messages between the stomach and the brain, they are, among other things, responsible for those ‘butterflies’ in the stomach and 95 per cent of the body’s serotonin supply, which contributes to happiness and well being. And there’s a good chance any imbalances in this super highway is associated with diabetes, cancer, autism and even Alzheimer’s.

So can you change your gut bacteria to help reduce your risk of getting certain diseases? A varied diet is thought to play a big part.

“We have some 100 trillion bacteria in our guts with diverse functions that aren’t just about helping to digest our food,” says Walker. “They help us have a healthy immune system, a happier mood and balanced hormones – and we can help them to help us by eating plenty of fibre, aiming for 5-7 fruit and vegetables daily (including plenty of prebiotic foods such as asparagus, peas, onions and bananas, which contain lots of soluble fibre) and drinking lots of water.”

Such is the importance of this bacteria-brain connection that it’s though one day analysis of your microbes will be as routine as a blood test, with doctors handing out personalised probiotics to help ward of anything you might get in the future.

Forget The Minority Report – soon we may have our very own Microbiome Report.



Originally published in Bitten ( in 2016

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