Program: Is farting a sign your gut microbiome is happy?

Tegan Taylor: So you know how I love my musical apparatus for our chats, Norman…

Norman Swan: Yes…

Tegan Taylor: I've got my Med diet bell here on the desk with me today. I forgot to bring my harmonica and my xylophone because I'm an idiot, but I did bring an extra new friend. Would you like to hear it?

Norman Swan: Yes, I think I do.

[Fart noise]

You're a rude wee girl.

Tegan Taylor: It's a whoopee cushion! We bought it especially for this particular episode of What's That Rash?.

Norman Swan: Where we answer the health questions everybody's got, and this time we were farting in front of a live audience.

Tegan Taylor: That's right. This chat comes from our recent live show at World Science Festival Brisbane. So this question came from John, and the question itself was read out by a lovely audience member at our live show.

Audience member: 'I am moved to ask a question of my own. We are urged to eat lots of fibre, to nourish the gut microbiome. Is flatulence a sign that the gut biome is well fed and happy? And will a happy gut biome really improve one's cognitive function?'

Tegan Taylor: John, you've asked that question so well. I'm going to give you a round of applause.

Norman Swan: But can we have the microphone back for a second? Why don't you just call flatulence for what it really is?

Audience member: Okay, a fart.

Norman Swan: Very good, thank you. Because I wasn't sure what you were talking about, to be honest.

Tegan Taylor: So, on that, it's a little bit like how we call cow meat 'beef' and pig meat 'pork' and that sort of thing, and I don't know if anyone's heard this story before but the reason we would do this is because after the Norman conquest, it was sort of fancier to speak in French, so around the table you would say the French word for cow, which was like bœuf, which became 'beef', or you would say the fancy word for pig, which was like porcine. And so in a similar way, the word 'fart' comes from Old English and Old German, the word was feortan, which meant to fart, it was probably an onomatopoeia, whereas 'flatulent' comes from the Latin flatulentus, which comes from a root meaning 'to blow', and we're going to blow hard today, Norman.

Norman Swan: We are. We're going to feortan a lot.

Tegan Taylor: What is a fart? 

Norman Swan: A fart is the expulsion of gas from your anus, and it's basically the excess gas from the bugs in your bowel. So you eat all this food, it gets absorbed in the small intestine, and then it goes into the large bowel, into the colon, and the bacteria in your bowel chew it up, and the bacteria produce gas, they produce hydrogen, they produce methane, they produce carbon dioxide.

Tegan Taylor: And hydrogen, which we'll come to later. There's actually quite a lot of research into farting. We'll get into some of it soon, but I did really enjoy this particular study that was done in 1998 where a US scientist called Michael Levitt used rectal tubes for a detailed study of fart compositions in six healthy women and ten healthy men. 

Norman Swan: Big study. Uncomfortable study.

Tegan Taylor: Big study. Would you like to know a rough volume of gas that was emitted from these people's…between 106 mls on the lower end, up to 1,600 mls, a litre and a half of air. The biggest farter produced over half a litre of hydrogen, which I think could be some sort of renewable energy source. The thing that really caught my attention, though, is that the smelly components of the fart were quite small, so together hydrogen sulphide, methanethiol, which smells like rotten cabbage, and the garlic-like dimethyl sulphide, on average, were just 50 parts per million of each fart.

Norman Swan: And only a third of them were really stenchy farters, weren't they?

Tegan Taylor: I think that you are foreshadowing research that we will get to, but before we get to legitimate research, I have to introduce you to the Invisible College of Experimental Flatology, which is a website that exists. When I first saw Flatology, I was like, is this some sort of flat-Earth society? No, it's the ology or the study of flat-ulence. Look, I don't know if the research is real, I don't really care. The fart charts are amazing. Let's look at one, please. If you have very quickly decoded this chart, I'm very, very impressed. But basically, for those who haven't, and for those who are listening without the benefit of visuals, what you're looking at here is the rate of farts at a dinner party, and you'll notice that there's a particular peek at the time of the evening where the ladies leave the table. They looked at the air quality during this time, so that's a little bit of a datapoint that you can drop around the dinner table, so to speak. So part of the question from John, who had such a beautiful voice, was about the microbiome. So we've talked a bit about what farts are, and I am very intentionally using the Germanic root here, we're not fancy, we're among friends. What about the microbiome? 

Norman Swan: In the microbiome we have millions and trillions of organisms. We tend to think of bacteria, but there's bacteria, there's viruses, there's fungi, and then there's these really weird ancient organisations called archaea, which we don't really know too much about, but they're in there as well. So, really, going back probably millions of years, we've got these bugs in our bowel, if you can call them bugs, and so this is plethora. But it seems to be bacteria, because they're more advanced in terms of their metabolism that produce the gases. And our microbiome is affected by what we eat, coming back to the question.

Tegan Taylor: What we eat feels…it's like we could take that a step further and have a reason to use some sort of…

Norman Swan: Well, it can be that the diet that is lots of vegetables, legumes…what would you call that diet?

Tegan Taylor: I think we would call it the Mediterranean diet.

[bells ringing]

I feel like I'm driving through a grove of bellbirds, it's beautiful.

Norman Swan: So, yeah, it depends on what bacteria you've got and what they're eating, and then they produce more gas when you're actually eating a healthier diet.

Tegan Taylor: Oh, so more gas is potentially a sign of a healthier diet?

Norman Swan: There's obviously a limit to it. If you're producing a huge amount…

Tegan Taylor: So more than 1,600 millilitres in a four-hour period…

Norman Swan: So it's hard to measure, but there are diseases like Crohn's disease, there's an operation called fundoplication, which is to prevent reflux, and for some reason a side effect of that operation is producing more gas, they don't understand why, probably because it changes the microbiome. But essentially, a healthy diet will produce more gas. So Blazing Saddles is right.

Tegan Taylor: Okay, you just said before that you don't really know what's good or normal, that if you're unhealthy in different ways, that can produce more gas and less gas. What do we know about how many farts a day is normal?

Norman Swan: Well, we've got the CSIRO to thank for this, who provided What's That Rash? with exclusive farting data…

Tegan Taylor: Farta.

Norman Swan: …from Australians. 

Tegan Taylor: So, this is the Chart Your Fart study that…there was an app, and it's Dr Brindal from CSIRO that we have to give credit to and our thanks for letting us bring you this What's That Rash? live show exclusive…

Norman Swan: Updated data. And you're all sitting on the edge of your seats with one cheek up…

Tegan Taylor: Well, you are.

Norman Swan: 19,000 people downloaded the Chart Your Fart app, and it recorded 471,000 farts. Because they're CSIRO and they're good scientists, they had to exclude…so they wanted a reasonable sample of farts, and so they excluded everybody who recorded less than three days, so it had to be more than three days. The average was about 10 days of farts, and they ended up with 6,000 people with 360,000 farts. So not bad data. So here's the question: Who produced more farts, men or women? Go on…

Audience: Women…

Norman Swan: Women? Do you agree with that? 

Audience: No.

Norman Swan: No? Men?

Tegan Taylor: Well, I think we need a show of hands. Who reckons men produce more farts? I notice all the women have their hands up. Who thinks that women produce more farts? All the men have their hands up. Interesting, interesting.

Norman Swan: So, for the sort of middle group of farts, that's two to seven farts a day, that was equal between men and women, but when they looked at the group that were producing nine or more farts a day…

Tegan Taylor: Super-farters.

Norman Swan: Women.

Tegan Taylor: Maybe they were more diligent in recording their data.

Norman Swan: Yeah, well, that's true, there could have been bias there. So, which age group would you say? If I were to say, you know, young people, middle age, older people…

Tegan Taylor: Old farts.

Norman Swan: So does the 'old fart' thing hold true. Clearly this room thinks so.

Tegan Taylor: What did the data say?

Norman Swan: 31- to 35-year-olds. God knows what they're doing. I am impressed they're eating a Mediterranean diet. So here's the question; which state in Australia had the smelliest, most lingering farts?

Tegan Taylor: This is an actual data point. If someone can answer this correctly, let's give them a magnet. Yell out the state you think…

Audience member: Tasmania.

Norman Swan: Tasmania? No.

Tegan Taylor: Someone said NT, someone said Queensland. No one has said the correct answer yet. No, not ACT. Did anyone say Western Australia?

Norman Swan: One person said Western Australia.

Tegan Taylor: Western Australia. They reported farts of highest stench and linger. I would have thought with a state that size, you would be able to get away from the smelly fart.

Norman Swan: And the time of day that you mostly fart? Well, it's sort of morning, mid-morning, and after dinner at night, pretty much reflecting our institute data there. So, really valuable data there on flatology.

Tegan Taylor: What I want to know then, Norman, given that we're normalising farting, we get a sense of the Australian…

Norman Swan: The room is feeling a bit…

Tegan Taylor: What happens if it's not the right time, and you just need to hold it in? Is that bad for you? Asking for a friend.

Norman Swan: So, here's what happens when you hold it in. The gas has got to go somewhere, because they continue to produce the gas, and what happens is your bowel absorbs gas, it goes round in your bloodstream to your lungs, and then you burp it out.

Tegan Taylor: Did you actually burp just then? 

Norman Swan: I was trying to, but…did you smell it? 

Tegan Taylor: I heard it.

Norman Swan: Yeah, eventually it gets out and comes out via the other end of your intestinal tract, your mouth.

Tegan Taylor: Incredible. Well, like I said before, there's some small amounts of compounds in your farts that make them smelly (highest stench and linger from WA, as we previously discussed), but one of the most abundant gases in a fart is hydrogen, and it has a really important role to play.

Norman Swan: It does, so it's not just being able to light your fart…

Tegan Taylor: As a doctor, would you recommend someone trying to light…? 

Norman Swan: Probably not. And is it partly myth? I don't know. You'd have to know you were a big hydrogen farter. So, hydrogen is actually quite important because the bugs in your bowel use the hydrogen as part of their metabolic processes. So, hydrogen gets recycled in your bowel, so it's quite important that you produce hydrogen, and, contrary to the study you just quoted from Pennsylvania, they reckon it's about a litre of hydrogen that we can produce a day, but it does get recycled, so you're not farting blue flame the whole time.

Tegan Taylor: So to come back to John's question, John wants to know if flatulence is a sign that the biome is well fed, and will a happy gut biome help one's cognitive function. We haven't talked about cognitive function at all, because we've been talking too much about the more important topic of farting. But to come back to John's question, what's our answer?

Norman Swan: Our answer is yes, it can, but not through farting. So a healthy microbiome, which is a very diverse microbiome, and the diet that we've been talking about produces a very healthy, diverse microbiome, and that produces a lot of different bioactive compounds, including what are called short-chain fatty acids, and these do go to the brain, and they settle down inflammation and oxidative stress. But also there's this complicated communication between the bowel and the brain using the nervous system and indeed the immune system. So, there's just a lot of crosstalk between the bowel and the brain, as you might imagine, since the brain needs the bowel to survive, we need the bowel to survive, so it's a very complex interrelationship. But it turns out that a healthy diet does improve your cognitive function, and the diet that really does this is called the MIND diet, and this diet is known to protect the brain, and it tends to be a bit like the Mediterranean diet, but there's a bias towards fermented foods and berries, particularly blueberries and strawberries.

Tegan Taylor: So in other words, the rich people diet. Well, thank you, John, for the question. One final piece of data before we go off this, which is all about acoustics, if you look at the screen you'll see a mathematical formula that shows us that simultaneous farts can sound like one single fart, and this is how you would calculate this. And to prove the point, I think if anyone here feels like they know how to make a…I would love to hear them all at once please, 1, 2, 3…

[fart sounds]

Norman Swan: And I suppose one of the other takeaways from this is that excessive flatulence can be a sign of problems in your bowel, one is irritable bowel syndrome, and there's not a lot you can do about that, but it's worth knowing whether or not you have it, and the other is celiac disease, where you are truly gluten intolerant, and that might be a sign that you want to get checked for that, which is a specific set of investigations, because you don't want to have celiac disease and not know it.

Tegan Taylor: Absolutely. It just goes to show that we can't be as comprehensive as we would always like to be on What's That Rash?. There's always more to learn, and we love it when we get your emails as well. Our email address is thatrash@abc.net.au.

And we've had an email about our recent episode on progressive exercise, Norman, from a few weeks ago. Ryan says, 'I don't go to a gym, I'm too shy for a public squat, so rather than spend a fortune on more weights, I'll just push on with my efforts, but with more time and reps. And thanks for the earlier episode regarding what time to exercise. I'm a 10pm, lounge-to-myself type of exerciser. So between both episodes, you've helped with my motivation and my back pain.'

Norman Swan: Oh, that's good.

Tegan Taylor: That's lovely. Thank you so much, Ryan, I love thinking of you squatting in your lounge at 10pm.

And some correspondence, Norman, from our other live show that was in the feed a few weeks ago on left-handedness vs right-handedness. Paul says, 'I'm a lefty,' (shout-out Paul, so am I), 'but it's a lot more complicated than people generally think. Most tools, hammers, saws, et cetera, I use left-handed. I can only write left-handed, so I am left eye dominant, but I can only shoot (whether guns or arrows) left-handed, and in fact my right eye can't even process what it sees down a scope if forced to use a right-handed rifle.' But Paul continues, 'I play left-handed at tennis, right-handed at cricket, and as far as I'm concerned it's the same grip on the bat and racket.' Now I'm standing here in the studio, Norman, trying to arrange my hands around a bat and a racket. Paul is very multi-talented, 'I naturally fence left-handed, but can only throw a ball right-handed, my left hand is useless for this.'

Norman Swan: So, Paul, I hope you've got well-controlled aggression here, with your swords and your guns, but…you know, carry on.

Tegan Taylor: Well, Paul has also been known to kick a rugby ball with his left foot, but plays soccer right-footed. 'I can only use scissors in my left hand, but eat steaks with the knife in my right hand usually, sometimes not.' Paul, you sound like a true Renaissance man, and I kind of like that you're mixing it up with your handedness along the way.

Norman Swan: And I could have picked you as a red meat eater.

Tegan Taylor: What is that meant to mean?

Norman Swan: We'll just leave it there, I think.

Tegan Taylor: And Gary, similarly…well, Gary doesn't mention quite as many extracurriculars as Paul, but Gary says, 'I'm right-hand dominant, but I kick a football with my left foot. Always have. And changing has been something best not discussed in public.' Well, Gary, now I just have so many more questions.

Norman Swan: Gary, you can write us a letter with a different name and we'll quote it.

Tegan Taylor: And, of course, if you do write that letter, the email address is thatrash@abc.net.au.

Norman Swan: We'll see you next week.

Tegan Taylor: See you then.