We all do it. Some more than others, with varying strengths of sounds and smell. But your farts reveal more about your health than you might think.
A typical fart contains a mix of gas from the air we’ve swallowed and gas that has been produced by our gut microbiome breaking down food we’ve consumed.
The oxygen and nitrogen from swallowed air is typically odourless, so it’s the products of our microbiome that give the flatus (the technical term for gas from the stomach and bowels) its signature scent.
The smellier components are the gases that contain sulphur. These are produced when bacteria break down sulphur-rich foods, including proteins found in dairy products, some grains and legumes.
If a three-bean chilli gives you farts that smell faintly eggy, it’s because your gut is busy breaking proteins into hydrogen sulphide.
Methionine, an essential building block for proteins found in dairy, fish and meat, is broken down into methanethiol, noted for a smell like rotten cabbage.
However, most protein in your diet will be digested and used as an energy source for your cells – it’s only when you over-consume protein that you’ll likely have a problem.
Carbohydrates can also produce a smellier fart when they’re fermented by gut bacteria. We all know that fibre is an important part of our diet, aiding digestion and, ahem, defecation.
Fibre feeds the good bacteria in the gut, but it’s broken down into fatty acids that can hitchhike on any gases escaping and contribute an unfortunate aroma.
Sugars and sugar substitutes will also result in gas if they reach the large intestine.
This is why people who suffer from lactose intolerance are often plagued by bloating and flatulence if they consume dairy, as the milk sugar isn’t digested by enzymes in the small intestine and is instead fermented by bacteria.
Your gut's secret signals
Provided you’re not over-eating protein and sugar, you can expect to fart on average between 5 and 15 times per day, expelling between 0.6 and 1.8 litres of gas.
Farts, in all their variations, are normal and natural. However, when they’re accompanied by other symptoms like painful bloating, constipation, diarrhoea or unexplained weight loss, they could be a sign of gastrointestinal issues.
These can include food intolerances and irritable bowel syndrome, inflammatory bowel diseases, coeliac disease and bowel cancer.
In fact, analysing the compounds that make up a person’s farts has shown promise in the ability to diagnose gastrointestinal conditions, according to a large meta-analysis published in 2023.
If your flatulence is causing you discomfort and you’ve checked with your doctor that there’s nothing serious going on, there are ways to reduce the amount of gas you produce.
The NHS recommends eating smaller meals and chewing slowly, exercising regularly and avoiding carbonated drinks like beer and sparkling water.
The bottom line is that farting is usually a good thing: a sign that our gut microbes are doing their job and aiding the rest of our digestive system.
But if you notice a change in your flatulence that coincides with other symptoms, it might be worth a trip to the doctor.
This article is an answer to the question (asked by Dafydd Thomas, Merthyr Tydfil) 'What do my farts say about my health?'
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