For most of us, it’s something to be politely ignored where possible.
But steering clear of flatulence is much more difficult within the confines of a rocket ship bound for the Moon, a problem highlighted last week by experts observing Nasa’s Artemis II lunar fly-by mission.
As well as a broken loo, which made disposing of waste a problem, the crew – like those on the Apollo flights of the 1960s and 1970s before them – faced the problem of circulating human gases that had nowhere to go. No laughing matter, as these gases are flammable.
Indeed scientists are increasingly taking farting (or flatus, as it’s known medically) more seriously – not just for astronauts, but as a vital indicator of the state of our health.
It’s an area of research in which one eminent American physician, Dr Michael Levitt, flew the flag for many years.
A gastroenterologist at the Minneapolis Veterans Affairs Hospital, he became known as the ‘King of Farts’ for his work before he retired in 2023. He even helped Nasa design astronaut suits made with activated charcoal to absorb gases emitted in space and stop crews from constantly breathing them in.
Generally speaking, passing wind is nothing more than a natural daily occurrence, a sign that the gut is working normally in releasing gas that would otherwise lead to abdominal discomfort.
But mounting evidence suggests that sometimes excess flatulence can be a sign of undiagnosed health problems ranging from coeliac disease (where the immune system reacts to gluten in foods, causing inflammation and a build-up of gas in the gut) to bowel cancer (where tumours can disrupt food digestion and lead to almost constant flatulence).
James Kinross, a colorectal surgeon at Imperial College Healthcare NHS Trust says ‘our colon is just a giant fermenting vessel’
‘For most of us, it’s a healthy bodily function,’ says James Kinross, a colorectal surgeon at Imperial College Healthcare NHS Trust and spokesman for the charity Bowel Research UK.
‘That’s because our colon is just a giant fermenting vessel. We lose about one litre of gas through farting every 24 hours.’
Now US scientists are hoping to shed more light on what our windy habits can tell us about the state of our gut microbiome – the large community of bacteria, viruses and fungi thought to play a role in everything from gut health to the strength of our immune system.
Researchers at the University of Maryland have developed a coin-sized gadget that sits inside underwear to carry out round-the-clock measurements on how often humans break wind.
The gadget – which comes in two parts that snap together through the underwear material – is placed next to the perineum (between the genitals and anus) and is packed with electrochemical sensors that monitor frequency and content of each fart.
The results are transmitted wirelessly to a database where scientists can monitor findings.
Preliminary results, published in the journal Biosensors and Bioelectronics: X, show that most of us break wind twice as often in a day than previously thought.
For the study, 19 healthy men and women wore the sensor in their underwear for 11 hours a day for one week. The results showed they passed wind an average of 32 times a day. Previous studies, which relied on volunteers self-reporting, had this figure at around 15 times a day.
And there was huge variation, too – one person broke wind four times in a day; another 59 times.
Now the US team is planning a more detailed study with 500 people called the Human Flatus Atlas project, which will also record the volume of gas released, how it varies from one person to another and what that might say about their gut microbiome. Stool samples will also be collected to shed more light on which microbes are responsible for excess gas.
‘We don’t actually know what normal flatus production looks like’ said Brantley Hall, an assistant professor in cell biology and molecular genetics at Maryland University
The objective, researchers say, is to eventually be able to use the device to compile a ‘fart score’ – an indication of health similar to blood pressure or cholesterol readings – and discover how we can alter the gut microbiome to our benefit.
‘We don’t actually know what normal flatus production looks like – and without that baseline, it’s hard to know when someone’s gas production is truly excessive,’ said Brantley Hall, an assistant professor in the department of cell biology and molecular genetics at Maryland University, who created the new device.
The sensor measures hydrogen (one of the main components alongside carbon dioxide, methane and nitrogen in farts), but they are developing a version that detects a range of gases. When we eat, the food gets digested and absorbed in the small intestine.
The residues from that process (such as fibre, certain carbohydrates and some proteins) that aren’t absorbed then move through to the colon, where bacteria and other microorganisms ferment them – producing gases in the process.
Some foods are more gas producing than others. In the case of vegetables such as brussels sprouts, cabbage and cauliflower this is because they contain a complex sugar (called raffinose) that we cannot break down easily.
When this undigested sugar reaches the large intestine, it’s fermented by the bacteria there. Baked beans have a similar effect.
For some people wind may be due to underlying medical complaints – such as lactose intolerance, a condition affecting about one in 20, where they lack a digestive enzyme (lactase) to digest sugar (lactose) in dairy, leading to a build-up of gas.
‘There are two main types of fart,’ says Mr Kinross. ‘There are those that are heavy in methane, which is largely odourless, and they tend to be associated with constipation.’ That’s because the gas, produced by gut microbes called archaea, prolongs the time it takes for food to pass through the gut.
‘Then there are farts with lots of hydrogen sulphide – the rotten-egg gas that gives an offensive smell,’ says Mr Kinross. ‘That’s often because people have too many of the wrong kind of bugs populating their gut, often as a result of getting too much of their protein from fatty meat [which contains sulphur-rich amino acids].’
As well as pungent wind, excess hydrogen sulphide gas in the gut can raise the risk of diarrhoea.
More worryingly, studies suggest the gas may be a key factor in the global rise in bowel cancer, traditionally a disease of older age, among those under 50.
The theory, says Mr Kinross, is that modern diets have led to higher levels of hydrogen sulphide in the gut and this can make healthy bowel cells turn cancerous.
As well as pungent wind, excess hydrogen sulphide gas in the gut can raise the risk of diarrhoea
A 2023 review in the journal Nutrients reported that several studies had found that Western diets full of fatty, sugary foods not only triggered changes in the gut that led to increased levels of sulphur, but that the gas caused damage and inflammation to the lining of the bowel that made it easier for cancer to develop.
Researchers warned: ‘Sulphur metabolism [in the gut] is recognised as a critical mechanism in early-onset bowel cancer in those under 50 – the incidence of which has been rising worldwide.’
Excess wind could even indicate ADHD – or attention deficit hyperactivity disorder – according to a study by the Chinese University of Hong Kong last year.
Researchers crunched data from 11 studies and found those with the disorder were 25 per cent more likely to have severe flatulence and symptoms of irritable bowel syndrome (such as tummy cramps) than people without ADHD.
It’s thought that the disruption to the gut microbiome that is responsible for excess wind is somehow also involved in the development of ADHD.
Certain medicines can also contribute to excess wind. Antibiotics can increase flatulence by disrupting the gut microbiome, for instance. And painkillers such as ibuprofen or aspirin can have a similar effect, possibly by irritating the lining of the gut.
However, breaking wind is also useful in certain circumstances.
For example, farting habits are already routinely documented on the NHS among patients recovering from abdominal surgery.
That’s because the stress of the operation and the strong painkilling drugs (such as opioids) used afterwards can slow down gut motility.
This affects up to one in four patients undergoing abdominal surgery and can cause vomiting, bloating and constipation – slowing recovery and extending their hospital stay.
Staff routinely quiz these patients on how soon after surgery they broke wind, as it’s a sign that the digestive system is returning to normal. Depending on the type of abdominal surgery, patients should be breaking wind after 16 to 40 hours.
Mr Kinross says temporary changes in flatulence – in terms of frequency, volume or smell – are not unusual.
‘But if it lasts longer than about six weeks – and especially if there are other changes in bowel habits, or it smells bad – then you should seek medical advice.
‘And whatever you do, try not to hold it in – despite the social stigma and embarrassment, it’s best to let it out.’ Holding it in often can lead to pain, bloating and constipation.
