Why is the study of the gut so important?
This is a big new area of health research. I’m interested in how the gut functions and how it’s controlled, the gut-brain-axis as we like to call it. I’m mainly looking at how the neurons in the gut function - how they control gut behaviour and how they communicate with the brain.
Understanding the gut-brain connections won’t be the magic fix to a whole bunch of diseases, but it’s an extremely important piece of the puzzle. Knowing more could reveal why some of the other strategies aimed at reducing diabetes, obesity or allergies such as asthma aren’t always effective. All these things seem to be tied up with the gut microbiota.
How can gut bacteria affect your mood?
Gut bacteria can affect some of the pathways that make up the gut-brain-axis. The gut is connected to the brain mainly through the nervous system - so for example, the satisfied sensation you get from a full stomach is due to the gut-brain connection.
The gut also talks to the brain by releasing hormones such as serotonin, which gets into the platelets in the blood to help with cardiovascular function, change metabolism and maybe affect mood.
The most common example of gut bacteria affecting your mood is if you change your diet. That is the easiest way to change your gut microbe make-up. Most of the gut bacteria are pretty picky and if you stop providing a particular population of bacteria with food it will starve.
When bacteria are starving they release toxins that get into the bloodstream and stir up the immune system to make you feel poorly. So your mood is affected, because the toxins are causing your physiology to change to sick mode.
On the flipside, it’s possible to overfeed a group of bacteria. But the gut is so full that the only way new bacteria can grow is if others make way. So it’s always a balance between the different bacteria fighting for their areas.
Do probiotics work?
Probiotics really don’t do much of anything. There’s been a big study recently, with healthy people eating yoghurt or using probiotics, that showed no change in the microbiota composition of their colon. The new bacteria hang around for a day or two, but then they’re all dead or gone away. Eating foods that feed those bacteria - what are called prebiotics - is a much more effective strategy than just eating bacteria.
How is the gut microbiota formed for each person?
The gut microbiota is mainly made up of bacteria that live in the lower gut or colon. It also includes yeasts, parasites, Archaea and most importantly viruses that infect the bacteria. There may be up to 10 times more viruses in the lower intestine than there are bacteria.
The gut microbiota forms at birth, but it depends on how you were born. If you’re born naturally, you pick up bacteria from your mother and if you’re born by caesarean you don’t pick up nearly so much.
If you look at gut bacteria within that first six months there can be a big difference between the two birthing methods and that’s the best clue of where bacteria are being picked up.
How easy is it to change your gut microbiota?
Some people try to change their gut microbiota by changing their diet and in fact they find out the gut has a certain role in cultivating its own microbiotia. The gut helps certain bacteria to flourish and it actually actively shapes the types of bacteria that are in there. So if you try to change it, the gut tends to come back to what it thinks is the right kind of bacteria.
On the other hand, the gut bacteria community is very reactive to your diet. If you give them a different food source - different prebiotics then different bacteria are going to eat that and grow up.
So in the end it’s a little unclear what’s going to happen in the long run because it’s easy to eat a healthy diet and change your gut bacteria. Whether you can keep it that way is the problem which needs more research.
What are the foods needed for good gut health?
This is where it gets quite boring. I got yelled at one time in a radio interview because after talking around the issue we got to the end and she said, “Is it just a healthy diet then?” and I said “Yes, it’s just a healthy diet!”
Specifically though - it’s a varied diet. So if you eat one particular type of fibre that’s only going to grow up to one type of bacteria. Whereas if you eat a whole range of fibres then that’s going to cause a large and more diverse community of bacteria to thrive.
Sugar seems to be the bad guy in a lot of commentary recently. Is to be avoided?
There’s no question that cutting down the actual sugar intake is a good thing. We sometimes get a little bit worried so we’re putting a half of teaspoon into a cup of tea, that’s not a lot of sugar compared to getting two litres of sugary drink at the servo and drinking the whole thing down twice a day, which is more typical in the US and some other areas.
What are you motivated by in your work?
I’m mainly motivated by understanding the disease processes, and the gastro-intestinal tract has quite a few diseases. The research we’ve been doing fits nicely with this new paradigm shift or this new idea that gut bacteria might have a more active role in disease processes. Up until now we hadn’t considered that the gut bacteria were having a great effect on the gut. We knew they were there, we just thought they were digesting food and helping you get some extra nutrients like B vitamins that are released by the gut bacteria.
But we didn’t appreciate the level of potential effect they might be having on the whole body and a lot of that seems to be through the gut-brain-axis.
Paul Bertrand is a Senior Lecturer in the School of Health and Biomedical Sciences at RMIT. Paul is a contributor to The Conversation.