The war inside your gut

Updated

Hundreds of bacteria species make their home inside our digestive system. But what do they actually tell us about our health?

Deep inside your gut, a war is going on. While you go about your daily life, Tolkienesque armies of gut bacteria are fighting to colonise vast wastelands of warm, wet intestine.

Your digestive system is about seven metres long — dank folded passageways filled with rotting food and faeces and slick with bile. Inside, more than 1,000 bacteria species scrap over rivers of your semi-digested waste. The species that emerge on top will decide whether your food is used for bodily good or evil.

In searching for answers to health issues in the microbiome, it pays to get down and dirty, take a few twists and turns, and end up a long way from where you started — much like this morning's breakfast.

There was a time where, if you'd asked me to provide samples of my blood, snot and poo to a complete stranger in the name of "journalism", I'd have said "yeah nah".

But after a years-long search for answers to a family health issue, I was ready to take one for the team and have my gut bacteria "profiled".

Power in numbers

Just like in human wars, the lines between what makes a good bacterium and a bad one can be blurred.

The bacteria once thought to be beneficial are now shown to cause devastation when they overrun our systems; some maligned bacteria we thought had been doing us harm may in fact prove a force for better health.

And then there's the question of what — if anything — we should do about the particular mix of gut bacteria we host. Can we tend to our guts fastidiously like gardens, consuming the right foods, and perhaps probiotics or prebiotics, to allow them to thrive with more "good" bacteria?

"Good" bacteria, the theory goes, reward our dietary choices by producing the metabolites that are integral to digestion and other essential bodily functions.

If we fill our digestive systems with the "right" kinds of food, the bacteria in our gut works in harmony.

If we haven't consumed the type — or perhaps more importantly texture — of food they require to thrive, our gut bacteria may work against us.

But just as conflict rages within our bodies, so it does without.

Scientific opinion on gut bacteria can seem as contradictory as it is pervasive. Depending who you ask, gut bacteria either play an important role in everything from digestion to the immune system, chronic disease, and even human behaviour and brain function, or they don't — at least not to the extent claimed.

Much has been made of the possibility of a link between gut bacteria and our predisposition to certain illnesses. But there's little in the way of consensus on what, if anything, changing our gut bacteria does to improve or harm human health, according to Australian experts in the field.

"Dare I say every man and his dog is interested in gut health and gut bacteria, so, with that comes the danger that a lot of people, a lot of companies, are on that bandwagon," says Dr Michael Conlon, a senior research scientist in food and health at the CSIRO.

"I think the key problem is that with any sort of area with promising information on health and disease, you get your people who are credible and those who are not.

"The major issue is it's suddenly a big industry, a big area of interest, and people are out to make a quick buck."

Sending your poo in the mail

Gut bacteria "analysis" has certainly gone mainstream. A simple Google search will find pages upon pages of companies offering to help you "understand and improve your unique gut microbiome" in four to six weeks.

One company says all you need do is mail them a "tiny amount of faecal matter from your toilet paper", and for $350 or so they'll look for evidence of everything from irritable bowel syndrome to Coeliac disease and parasitic infection.

It all seems so easy. You'll have the keys to your gut bacteria kingdom in a month.

Instead of joining the hordes sending their poo by mail for testing, I'm heading to Griffith University's Gut Health Clinic immunologist Dr Nic West, who has devoted his professional life to researching gut bacteria and health.

The aim of the Gut Health Clinic and similar research at other universities is to build a population-based data set that allows us to identify whether there are trends in the microbiome associated with health and disease.

The profile Dr West and his team will build of my gut will take six to 12 weeks to complete — much longer than most tests available online. The process involves keeping a three-day food diary, a full physical, blood samples, allergy testing, a nasal wash, and — ratcheting up the awkward factor — a faeces sample, handed in person to a complete stranger.

When the profile is finished, I will have usable data that might, say, guide my dietary or supplement usage — under the guidance of a dietitian. Still, Dr West insists, the test doesn't prove any link between a person's microbiome and their health.

"There are reports now about companies that will try to give you a disease risk score based on the presence or absence of a specific bacteria, which is unethical, and almost tantamount to fraud given current biomedical research," he says.

He also notes that a key limitation to microbiome research lies in the different approaches to analysing gut bacteria between researchers which often means two very differing sets of results for the same sample.

'It's like climbing Mount Everest'

Gastroenterologist Terry Bolin has staked his medical reputation on the idea that gut bacteria have an influence on human health, as founder and chairman of non-profit research group The Gut Foundation. But he's just as circumspect about the progress medical science has made.

"It's like climbing Mount Everest, where you're at Base Camp and there's a long, long way to go," says Professor Bolin, whose research has focused on the small intestine.

"We believe [gut bacteria] do have a potential role in mental disease, psychological problems, anxiety, depression. They do have an influence on weight gain. And they may have a potential influence in preventing cancer and possibly disorders of the colon like colitis. They are greatly influenced by a good diet, and a good diet means a variety of foods including grains, vegetables, fruit, lean meat.

"But we don't yet know whether all the claims about the microbiome are, in fact, true. Nobody can really predict from your microbiome what's going to happen to you."

Dr Conlon from the CSIRO adds that one area in which all sides should exercise restraint is when discussing any potential links between gut bacteria and the brain — especially for treatment of autism, ADHD, anxiety and depression.

Dr Conlon himself was a subject in a study a decade ago into possible links between gut microbes and autism and lamented the unstructured rush by non-experts — desperate parents and well-meaning medical professionals alike — to understand the "gut-brain axis".

"There's so much more research that needs to be done to understand how what you're eating affects the microbes, and how that then influences mood, behaviour, etcera," he says.

Beyond what individuals eat, the toll of a Western lifestyle on the microbiome has also been of interest to gut researchers .

"Research in the US has focused on indigenous tribes," says Dr West. "Comparisons of the faecal microbiome and diet with Western society, in this case cities in the US, has identified quite striking differences between the microbiomes of the two groups, with the indigenous tribes having a greater variety of species than their city living counterparts," says Dr West.

"But then you've also got a completely different health profile. These people still suffer from infectious diseases that we've eradicated now a long time ago. It provides some historical context to understanding how the microbiome has changed with industrialisation."

Where matters as much as what

Before entering a conversation with an expert about gut bacteria, it pays to look up the term "dysbiosis".

"Dysbiosis means that something's out of whack, so you potentially have had a particular microbe or set of microbes that have been able to establish themselves when they really shouldn't be there, or are causing problems," Dr Conlon explains.

The word comes up a lot when you're talking about the clash between the species of bacteria inhabiting the gut: it's not just what bacteria they are, but where.

"We've had quite robust debates around this idea of dysbiosis," Dr West says.

"The effect of our gut bacteria can change from positive to negative based on their location in the gut, their abundance in relation to other bacteria around them and from dietary, supplement or medical effects. Given that research is still identifying new species, it is not appropriate to make a diagnosis that an individual has dysbiosis.

"If you can't define a healthy microbiome how can you suggest an individual's gut bacteria is out of balance?"

Dr West is certain of the potential of gut bacteria research, but unsold on the practical applications. A medical case can be made, he says, in only a few small areas of human health, such as using probiotics to treat traveller's diarrhoea, or reducing the risk of the common cold, but only in some highly stressed groups.

So do I have a healthy gut?

So what did all this pooping in bags, snorting in bottles and divulging my complete lack of adherence to a remotely balanced diet reveal?

I am staggeringly average.

The general health check suggests I'm in good enough physical shape, despite Dr West initially setting me up for an unflattering comparison ("We work a lot with athletes").

When it comes to the contents of my gut, that's pretty average too, although I do skew markedly higher than the wider population on some species, and lower on others.

No signs of the pathogenic bacteria species salmonella, campylobacter, shigella and clostridium difficile, which I can only imagine is a good thing. Streptococcus, yes, but lose the battle win the war, eh?

My report also comes with a handy link to some allied health services to help me in "adopting healthy lifestyle practices" should I need them, although based on those positive earlier comments about my general health I can surely afford to wing it a while longer.

None of the information contained in the report by Dr West's team can provide me with a firm understanding of what illnesses I am prone to contracting or diseases I'm likely to develop, or whether my physical or mental health is in any way affected by the contents of my gut.

What it can do, Dr West says, is to detail the make-up of an unquestionably central component of my health — and add to a growing body of scientific knowledge.

"Without including genomics information, which no commercial providers we have looked at provide, there is the potential to cause undue stress and concern.

"We're talking millions, or billions, of bacteria in a mass that's equivalent to any organ in the body," he says.

"And that's what all this microbiome profiling is all about — to say, well, what is the role of this organ in keeping us healthy?"

Dr West says the momentum behind microbiome research at least offers some hope of more breakthroughs.

"It's about how we can develop interventions that are safe and that will lead to meaningful changes in people's health," he says.

"If the many microbiome research programs within universities can identify gut bacterial species that reduce illness or improve the effects of pharmaceutical intervention, such as immunotherapy, then the gut microbiome field will move into mainstream medicine."

Credits

Words by Freya Petersen

Illustrations by Edwina Seselja

Edited and produced by Leigh Tonkin

Topics: health, diet-and-nutrition, irritable-bowel-syndrome, food-safety

First posted