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The facts on farting

Let’s clear the air! Dietitian Brooke Longfield answers the questions you’re too embarrassed to ask.

We know — you’d prefer not to talk about this, and no one wants to smell it, but there’s no denying it: we all fart. Yes, passing wind in public is poor etiquette, but that unwelcome gas signals a healthy diet and digestive system.

Still, everyone’s different and while some of us claim not to fart (ever!), most people average 15 times a day. For some of us, this number can climb as high as 40.

Why do we fart?

Breaking wind is completely normal and there are two causes: the air we take in and the gas we create. When we eat, drink or swallow saliva, we also ingest air, which travels into the gut. The body expels the excess air through burps and farts.

Intestinal gas is a natural by-product of digestion. When gastric juices and stomach acid combine to break down our food, the process releases carbon dioxide. As food passes through the colon, trillions of gut bacteria feed on and ferment it, producing oxygen, hydrogen, nitrogen and more carbon dioxide, along with that telltale sulphurous odour.

What about fibre?

Yes — the amount of gas we produce depends on the amount of fibre we eat. Foods that contain lots of fibre, such as fruit, veges and legumes (which include beans, lentils and chickpeas), are harder for the small intestine to digest than highly refined foods such as white bread. So, when fibre-rich foods move from the small intestine into the colon, their indigestible bulk becomes fodder for gut bacteria.

“Farting can be a sign of a healthy gut,” explains gastroenterologist Terry Bolin, president of The Gut Foundation in Sydney. Flatulence is a small price to pay for eating plenty of gut-friendly fibre.

This essential nutrient not only boosts the number of ‘good’ gut bacteria, which are vital to strong immunity and good mood, but also helps prevent constipation and reduce your risk of bowel cancer and diabetes.

What’s normal?

“There’s a huge range of normal when it comes to farting,” Dr Bolin says. Our intestines can produce anywhere from 500ml to two litres of gas every day. This mixture of gases can sometimes contain sulphur, the compound that gives farts their offensive smell.

Men tend to expel more gas, reporting an average of 12 emissions a day in one of Dr Bolin’s studies, whereas women average seven. Why? Dr Bolin says, in most cases, men eat more cereal fibre than women, and their bowel muscles get rid of gas more quickly.

Cereal fibre is present in grain-based foods.

“Women are generally more socially aware about farting than men are, so they often hold it in,” says Dr Bolin, warning against this because it only causes more bloating and discomfort.

Women are also more susceptible to bloating, a build-up of gas (in the small or large intestine) that they’re unable to pass.

Help! My farts are…

Loud: The pressure of passing wind can cause a surprisingly loud noise. As socially unacceptable and embarrassing as this is, it’s usually out of your control. The good news is that a loud fart doesn’t necessarily have a bad smell! And you can always try passing gas with a little less force.

Stinky: Certain foods produce more-offensive gas than others — think sulphur-containing veg, such as cabbage, Brussels sprouts and broccoli. Spicy curries, garlic and onion can also result in strong-smelling wind, as can dried fruit, long-life juice and deli meats that contain sulphites.

Frequent: Excessive flatulence is usually due to a high-fibre diet, but it can also indicate a digestive disorder. Holding in farts only causes bloating and discomfort, so talk to your doctor if intestinal gas is becoming difficult to manage.

The dog did it!

That unpleasant rotten-egg smell is mainly a result of eating foods that are high in sulphur. The usual suspects belong to the brassica family of veges, which counts cauliflower, broccoli, bok choy and Brussels sprouts among its members. Other sulphur-rich foods include meat, eggs, cow’s milk, cheese, onions and garlic.

These kinds of everyday foods can make sulphur hard to avoid, but you can try to limit the foods that contain this compound as a preservative. Watch your intake of dried fruits and processed deli meats, all of which can produce an ill wind!

Luckily, our farts aren’t always stinky.

“Aroma isn’t necessarily important,” Dr Bolin says. “Only four in 10 people emit smelly gas.”

Main offenders

Experiencing a little more wind than usual? These common gas triggers could be to blame.


Beans, lentils and chickpeas are notorious for their ability to cause bloating and wind thanks to their high fibre content. Despite this, you may not need to avoid them altogether. Many people tolerate canned legumes better than they do dried varieties. Just give them a really good rinse to wash away the concentrated canning liquid.

Dairy foods

People with lactose intolerance are unable to digest the natural sugar in cow’s milk. This means that dairy foods ferment in their bowels, causing abdominal pain, wind and even diarrhoea.

This food intolerance is more common among people of Asian descent.


Some people have difficulty digesting FODMAPs, a group of naturally occurring sugars that can wreak havoc on the gut. This means they need to limit or avoid FODMAP-rich foods, such as onion, garlic, wheat, honey, legumes, broccoli, Brussels sprouts, pears and apricots.

Diet yoghurts, muesli bars and chewing gum can also be problematic because they often contain FODMAPs in the form of food additives, including inulin, sorbitol and xylitol.

When the small intestine fails to absorb FODMAPs, they travel straight into the large intestine. Here, they become food for gut bacteria and ferment, producing gas that gives rise to bloating and excess flatulence.

FODMAPs can be particularly troublesome for people who have irritable bowel syndrome, and IBS itself can cause excessive wind.

If you think you’re sensitive to FODMAPs, see a dietitian or registered nutritionist so you don’t start avoiding a wide range of healthy foods for no reason.

Fibre supplements

Metamucil, Benefiber and other fibre supplements can bring on a bout of tooting, as can a sudden influx of fibre-rich foods. If your diet is low in fibre and you want to take a fibre supplement, begin with the minimum starting dose and slowly increase your intake. This will give your bowel time to adjust to its new workload.

Bottom line

Remember that what’s normal for one person isn’t necessarily normal for another. If you notice any worrying changes, such as painful bloating, increased wind (while following your usual diet) or abnormal-smelling gas, talk to your doctor. At this stage, you need to rule out any underlying digestive conditions, such as IBS, lactose intolerance and coeliac disease, before making drastic and potentially futile changes to your already-healthy diet.

Of course, it’s vital to seek help when gas starts to interfere with your quality of life.

Five tips for a healthier (and quieter!) gut

1. Chew your food well

The more quickly you eat, the more air you swallow, sending gas swirling down into the gastrointestinal tract. Digestion starts in the mouth, so make sure you chew slowly and wait a few moments between mouthfuls.

2. Add fibre gradually

A sudden switch from a low to high-fibre diet can make you fart more than usual. Increase your fibre intake in stages to help your gut bacteria and digestive system adjust.

3. Move more every day

Regular exercise, such as walking, aids digestion by stimulating the intestinal muscles. Certain yoga positions can also help relieve gas, bloating and abdominal pain.

4. Avoid fizzy drinks

Carbonated soft drinks, mineral water and beer can cause gas to build up in the intestinal tract. Excess air can enter your gut when you drink through a straw, too.

5. Cut back on sweeteners

Ever noticed the fine print on packets of artificially sweetened gum and lollies? It’s a warning that if you eat these products in excessive amounts, you’ll probably suffer from comparable bouts of wind and diarrhoea.

Did you know?

  • The small intestine can fill with up to three litres of gas — enough to blow up two party balloons!
  • Onion, garlic and legumes can cause excess wind and bloating in people who have irritable bowel syndrome.

You may also be interested in:

Foods that help you poo

Digestion – are you normal?

Bristol stool chart

Diverticulitis causes and what to eat

How to cure constipation

Article sources and references

Date modified: 22 November 2021
First published: Feb 2017


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