The English language is full of references that link guts and brains - ‘I feel gutted’, ‘What’s your gut reaction?’, ‘That news left a bad taste in my mouth’, and so on. Even the old adage, ‘The way to a man’s heart is through his stomach’ emphasises the importance of a feeling well fed to how we feel emotionally. Yet, the complex, highly evolved biological interplay between brain and gut is, surprisingly, only now being fully unravelled to reveal its intriguing secrets. Much of this interplay is dictated by the microbes we play host to, especially the bacteria. And since the human body has 10 times more microbes than human cells, perhaps it’s a case of, ‘The way to a man’s heart is through his brain via his stomach – with help from the right bacteria’.
Increasingly, scientists are finding that what’s inside our guts will impact on our behaviour and emotions – as well as our long-term health, even influencing our risk of developing conditions such as Alzheimer’s. And with levels of depression, anxiety and obesity at record levels in Western society, we’re hungry to know more. And who knows; in future, we may be able to tackle psychological or emotional disorders via treatments that target the gut, rather than the brain or nervous system.
I embark on this blog having finished the highly entertaining best-seller, Gut: the inside story of our body’s most under-rated organ, by young medic, Giulia Enders. It caught my eye in the window of a bookshop whilst suffering from something of the gastric variety. This I blamed on being too curious and trying raw shellfish at an Italian wedding. ‘When in Rome’, I had thought, tucking in… Fast forward two months, and I set aside my normal concerns about antimicrobial resistance, and embarked on a course of antibiotics to try to end the symptoms. Later on, in an attempt replace some of the ‘good bacteria’ I’d nuked, I took a course of well-researched probiotics. Whether due to the probiotics or other factors, fortunately, after three months, my symptoms subsided, and, with them, an accompanying gloom which often goes with a gastric complaints – and for reasons Enders’ book helped to explain.
WE ACT WHAT WE EAT
Which brings us back to the book. Giulia Enders’ fascination with the gut was partly triggered by attending a medical student party, during which she chatted to a fellow student with the worst bad breath she’d ever encountered. Enders was soon to learn that the poor young man died only hours later, having taken his own life. Was there a link between his severe depression and the contents of his gut emitting those foul gases?
Despite its tragic start, the book is littered with scatological humour to keep things light, childish jokes about poo and puke, and ‘cute’ line drawn illustrations by the author’s sister. But, there are some serious, take-home facts woven through. Suddenly, the world is waking up to the links between our behaviour and what we eat. This goes far beyond questions such as, ‘Have you consumed too much caffeine today, Mr Tetchy?’ and into the fascinating realms of what we eat, how we eat (leisurely, or in a rush), how we expel its waste (sitting or squatting) the antibiotics we are exposed to, and other factors can influence weight-gain, obesity, and major lifestyle diseases including depression and anxiety.
‘ZOMBIE’ MICE: A CURIOUS TALE OF WHAT WE EAT
A particularly fascinating example that Enders gives involves the parasite, Toxoplasma Gondii, – single celled organisms that reproduce in the gut of cats, and can infect humans should they eat raw or unwashed food. (We can only be infected once, and the chance of us having been infected is the same as our age, in percentage terms.) Whilst initial infection may only produce flu-like symptoms, toxoplasmata can infect the brain of the host, and interact with neurotransmitters there to influence behaviour.
In an example of evolution at its most sophisticated, toxoplasmata modify dopamine and serotonin pathways such that infected mice are led towards cats in ‘suicidal fashion’ thanks to a reversal of their normal aversion to the smell of cat urine – ensuring cat can eat mouse, thus perpetuating the infection cycle. Humans who’ve been recently infected are more likely to be involved in a road traffic accident, or other event involving judgement of risk. Indeed, its effect on the brain is such that the proportion of toxoplasmosis carriers among schizophrenics is about double that seen in non-schizophrenics.
In Enders’ words, “Toxoplasmata can influence us far more than we ever thought possible a few years ago: And they have rung in a new scientific age: an age in which a crude lump of cat faeces can show us how susceptible our lives are to change…. we are just beginning to understand just how complex the connections are between us, our food, our pets, and the microscopic world in, on, and around us.”
The following nuggets are more than simply food for thought. At Curious PR, we predict they will increasingly influence healthcare priorities, policy and treatment in the future.
EXPOSE THEM YOUNG
Establishing good gut bacteria in childhood is crucial, which points to more cautious use of antibiotics in infants and children. Indeed, for anyone who is pregnant and faces the certainty of a C-section, it’s worth knowing that naturally-delivered babies receive their first major immune ‘event’ by being bathed in the secretions of the mother’s birth canal. Specifically, the lactic acid found naturally in this region provides a first, important step towards priming baby’s immune system, and thereby avoiding allergies as well as infections. Newborn C-section babies may have beautifully shaped, un-squashed heads, but for the first 3 years of life, they will lack the gut bacteria found in babies delivered normally. (Bear in mind, some UK hospitals have a 25% C-section rate.) As such, some parents now choose to wipe their newborn C-section babies with the mother’s birth canal secretions to try to simulate this event.
SQUEAKY CLEAN’S BAD
Mice reared in sterile surroundings (to eliminate normal bacterial colonisation of the gut) become obese, and their behaviour becomes hyperactive. Yet, injecting the stomach contents of a ‘normal’ mouse into that of its ‘squeaky clean’ counterpart will normalise the ‘clean’ mouse’s behaviour and body mass. Furthermore, if a thin mouse is given the gut bacteria of a fat human, it too gets fat. Now, one needn’t be a scientist to note the implications… A study involving mice twins, published in Science in 2013, provided solid evidence that the gut microbiome (its organisms and their genetic material) is involved in weight gain. The foods we eat (or don’t eat) influence which types of bacteria and in what numbers they exist, in our guts. Experts are asking whether changing our gut bacteria could influence the foods we crave, and therefore whether or not we become obese or overweight. Not so much ‘chicken or egg?’ but ‘chicken or donut?’
DIRT IS GOOD
So, how far should we go to promote a healthy bacterial balance? Experts on the side of ‘the hygiene hypothesis’ believe our daily lives have swung too far in the hygiene direction, which has starved us of regular contact with ‘helpful’ microbes. So, how about embracing the ‘Don’t Wash Your Hands’ theory? A recent article in The Times quotes Tim Spector, professor of genetic epidemiology at King’s College London on the subject of domestic hand hygiene. ‘I don’t think we should be washing out hands before a meal now. Food poisoning incidences in the home are incredibly rare. We are over-cleaning enough… We have to start striking a different balance because our sterility is causing problems.’
IT’LL ALL COME OUT IN THE WASH
In conclusion, it’s worth remembering that a sizeable 4lb (approximately 2kg – more than our brain weighs) of our gut contents consists of bacteria. They are highly important 2kg contribution to our health, and we must learn more about their link to metabolism, obesity, and other areas of health – including, ultimately, whether we are happy, fit and healthy. Enders makes some compelling arguments for not throwing the baby out with the bathwater, and keeping the right balance of bacteria in our lives. Yet, it’ll take major changes in attitudes and habits to achieve this, in cultures where the Victorian idea that ‘cleanliness is next to godliness’ prevails.
Giulia Enders, interviewed by TVO – Ontario’s education channel