What makes farts smelly or noisy? And is it safe to hold these in?

What makes farts smelly or noisy? And is it safe to hold these in?

How many times do you fart in a day? Are men's farts really smellier than women's? CNA Lifestyle asked the experts everything you wanted to know about flatulence but were too shy to ask.

What does your fart say about you? (Illustration: Jasper Loh)

Whether you try to hold it in, release it stealthily or blast it with abandonment, everyone farts. In fact, the average person toots to the tune of 15 to 23 times a day without realising it, said consultant gastroenterologist Dr Gwee Kok Ann from Gleneagles Hospital.

“Generally, people only perceive an increase when they pass double the usual average,” he said.

So just how much gas are we contributing to the environment? “The volume of each normal fart is between 5ml and 300ml, and over 24 hours, the majority of people can pass 400ml to 1,500ml of gas,” he said. For comparison, each normal breath you take is about 500ml of air.

The spread of a fart’s odour can be tremendous as a fart can be expelled as fast as the speed of sound.

Make all the wisecracks you want but flatulence is a normal process, according to Dr Daphne Ang, senior consultant with Changi General Hospital’s Gastroenterology and Hepatology Department. 

“Intestinal gas occurs when we swallow food or water as small amounts of air are swallowed together. Gases also build up during the digestion of food,” she said.

So yes, you have been breaking wind since you were born. But we bet there are some things you have been too embarrassed to ask and secretly want to know. Don't worry, we've asked them all for you.


You may have heard the saying: If it smells, it won’t be noisy; if it’s noisy, it won’t smell. Turns out, that’s just a bunch of hot air. 

The two have no connection whatsoever. Instead, “the sound of a fart is influenced by the tightness of the anus’ opening and the force of gas expulsion,” explained Dr Gwee.

READ: This potential weight-loss treatment involves eating another person's poop

It's also about the amount of gas being passed, and definitely nothing to do with the size of your bum. “An excessive amount of gas would naturally result in more noise than small amounts of gas. The size of a person’s posterior is non-contributory,” said Dr Ang. 


If you’ve cut the cheese and tried to make a swift exit to avoid being detected, you’d know it doesn’t work most of the time – because you’ll be too slow.

“The spread of a fart’s odour can be tremendous as a fart can be expelled as fast as the speed of sound. Much also depends on the volume of gas passed,” said Dr Gwee.

While there isn’t a way to know how much gas is passed, Dr Ang said that “most of the gasses are odourless and released in small quantities, making them unnoticeable”. “However, if the gas contains sulphur, it will be associated with a bad smell and can be socially embarrassing,” she added.


What about the times you've had to hold things in? Will there be trouble to pay for? “While attempting to hold it in may cause the individual to feel uncomfortable, whether it leads to colonic diseases is unclear,” said associate consultant Dr Alex Soh from National University Hospital’s Division of Gastroenterology and Hepatology.

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But if you've got gas to let go, it's just best that you do – to avoid possibly embarrassing yourself in front of other people. Said Dr Gwee: "The accumulation of gas could potentially cause the person to lose control and leak stool and gas, causing a great embarrassment." 


Both are guilty – but in different ways. Your diet definitely determines how much gas you pass, especially if it includes foods that contain high amounts of poorly absorbed carbohydrates, said Dr Ang. 

“These undigested carbohydrates pass into the colon, where intestinal bacteria ferments them, and leads to excessive flatulence.” Beans and lentils are key sources of such carbs as are vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts and onions, she said.

That's not all that these foods can do to you. In addition to increasing the amount of gas in your digestive system, their high sulphur content also makes your gas smell, said Dr Gwee.

Undigested carbohydrates pass into the colon, where intestinal bacteria ferments them, and leads to excessive flatulence.

Meanwhile, you might want to keep an eye on your protein intake if you're concerned about smell. 

“A high-protein diet, which is a common fad these days, can also be associated with an odour,” said Dr Ang. “This is because proteins are digested at a much slower pace than carbohydrates. As bacteria ferments protein in the colon, nitrogen is produced and results in an odour.”

And obviously, carbonated beverages such as soft drinks, beer and champagne would contribute to flatulence as they contain air bubbles. The same gas-aggravating situation also applies to foods and drinks that have added sweeteners, which diet soda, sugar-free chewing gum or even artificial sweeteners do, said Dr Ang.


When it comes to who farts more, “age and gender did not have a significant influence on the frequency of flatulence”, said Dr Soh.

But there's a difference when it comes to smell, apparently. You might not automatically associate farting with women, so all that odour has to come from the men, right? 

Wrong! Women may actually produce smellier farts. “This is likely due to a combination of women having more constipation and a preference for vegetables,” said Dr Gwee. “The smell is determined by how long the stool has been retained in the rectum.” And because constipated individuals tend to eat more greens to alleviate their bathroom situations, they end up with smellier farts.


If flatulence is causing you embarrassment in social situations, Dr Ang suggested taking charcoal tablets "as they absorb gas from the intestinal tract". 

"Most cases of excess gas do not imply anything serious. However, you should visit your doctor if you have persistent abdominal pain, recurring episodes of constipation or diarrhoea, passage of blood in the stools and/or unexplained weight loss," she said.

Source: CNA/bk