What causes farts, and what can they tell you about your health?

Passing wind might be considered taboo — and might even elicit a giggle — but there’s a serious side to farts and what they can tell us about our health.

Changes in their smell and frequency can be helpful indicators to healthcare professionals of what’s happening deep inside our gut.

And even if you feel like you’re constantly releasing pressure from the old gas tank, evidence suggests that copious farting isn’t necessarily a bad thing.

To find out exactly what a typical daily fart tally looks like, researchers from the CSIRO last week released an app called Chart Your Fart, where users can track the number and smelliness of their toots.

Let’s uncover what passing wind can tell us about the state of our gastrointestinal tract.

What is a fart?

The gas that becomes a fart is produced mostly by bacteria inside our gut.

Brewing a fart is a complex process, and unique to each person, according to Emma Beckett, a food nutrition scientist at the University of Newcastle. 

“It’s super complicated. There are so many different types of bacteria, as well as fungi and and viruses [involved].”

Various gut bacteria produce a number of gases including hydrogen, methane, and carbon dioxide, mostly inside the colon.

Small amounts of swallowed gases from the air, such as oxygen and nitrogen, can also be introduced to the mix.

This gas moves through our intestines towards the anus, where it is released through the sphincter as a fart. 

What causes those terrible smells? 

Occasionally, a bad case of wind can clear a room. 

It’s called hydrogen sulphide, also known as rotten-egg gas, that cause those real stinkers. The larger the percentage of hydrogen sulphide making up the fart’s composition, the worse the smell.   

But while you can partially blame your collection of microbes for your stinky farts, what you eat is also a contributing factor.

Some foods are more likely to cause smelly farts than others. For example, people who suddenly eat more meat, or increase their intake of protein using powders, experience particularly stinky gas in what’s known as “protein farts”.

Plant-based diets and farting

An increase in flatulence is a “very normal” part of transitioning to a plant-based diet. But it doesn’t mean you should give up on going meat-free — here’s how you can keep the beans, but dial down the gas.

In a 2018 study, Melbourne researchers discovered that cysteine, an amino acid found in high levels in meat and other animal protein, increased the production of hydrogen sulphide significantly when mixed with human faecal samples.

While more research will need to be done, the team noted in their study that this may be due to cysteine being eaten by specialised protein-fermenting bacterial species, which produce hydrogen sulphide as a by-product.

There are also medical conditions where symptoms include changes in farts.

If your farts are particularly smelly or frequent, they could be a sign of irritable bowel syndrome, coeliac disease, an infection or an intolerance, according to Rajaraman Eri, microbiologist and food technology researcher at RMIT University.

“Farts are indeed a good indicator of what is happening inside the gut with respect to one’s digestibility, bowel movements and importantly, the status of the microbiome.”

How often do people typically fart?

Textbooks suggest that somewhere between five and 20 farts each day is “normal”, but there’s not been a whole lot of research looking into fart frequency specifically, according to CSIRO researcher and behavioural scientist Emily Brindal.

“There’s a lot of curiosity about flatulence but it’s never something that’s really researched in its own right.”

To get a better idea of what the average Australian lets rip each day, her team created the Chart Your Fart app. The citizen science initiative asks people to log their farts across a minimum of three days, including one weekend day. 

Why am I bloated?

Up to 30 per cent of people of all ages experience bloating. So what might be behind that bloated feeling? 

Dr Brindal says the weekend day is included because we act (and therefore fart) differently between weekdays and weekends.

Being active, like going on a hike, run or just a walk around the block, helps get rid of trapped gas. 

“People eat differently and do different things,” she said.

“You’d probably not sit on an office chair all day [on a weekend], for example.”

And on top of the lack of movement during the week, an office worker might fart less during standard business hours if they sit among colleagues.

While five to 20 farts a day quoted in textbooks might seem like a broad “typical” range, Dr Brindal said most of us would sit in the lower and middle brackets. 

And that’s not necessarily a good thing, because it shows our diets are lacking in fibre.

Why farts and fibre go hand in hand

There are a few different types of fibre, but some contribute more to farts than others.

One of these is resistant starch, which is fermented by our gut microbes. In doing so, they produce compounds called short-chain fatty acids which are, in turn, used by cells that line our colon for energy, and help maintain colon health.

But a by-product of the fermentation process is gas. The more resistant starch you eat, the more gas you’ll likely produce. 

How does your diet affect your gut bacteria?

What foods should we eat (and avoid) to keep our gut health in check?

Foods high in resistant starch include lentils, wholegrain cereals and, of course, baked beans. 

“It’s unfortunate that they do have the reputation as gas producers, because they are health promoting and cheap,” Dr Beckett said. 

“Beans are super high in fibre which is why we want people to eat more of them.”

Australian guidelines recommend eating between 25 and 30 grams of fibre each day, and most of us fall way short.

Eating too much fibre too quickly can generate bloating and loud farts, but gradually increasing dietary fibre and soaking dried beans before cooking them, which helps break them down slightly, could help dial the gut gas volume down.

Dr Beckett suggests that we should all eat more fibre, and that means accepting more farts too.

“It would be great if people could get past the gassiness,” she said. 

“Eat the fibre, accept the farts.”

Is it OK to hold in a fart? 

Despite being something everyone does, farting is not appropriate in certain situations. The number of times someone might let gas burble back up instead of releasing it is socially dependent, Dr Brindal said. 

“[Fart frequency is] a mixture of what you’re putting in [your body], but also movement, and how relaxed you feel.

“When you’re locked in a room with your boss, versus when you’re out hiking — they are two very different scenarios.”

While you might be tempted to hold farts in to avoid embarrassment, this isn’t recommended. 

Keeping gas inside you is likely to make you more bloated.

There’s another compelling reason to fart it out — gas that isn’t released from your anus is absorbed by your body, and ends up coming out in your breath. 

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