Men fart more and have larger poops when following a diet enriched in plants, researchers have found. The reason for their inflated gassiness – if you’ll pardon the pun – is a greater number of healthy bacteria setting up camp in their guts.
It’s been widely assumed that a plant-rich diet can have these malodorous effects on our bodies for some time – who could forget the playground ditty “beans, beans, good for your heart, the more you eat the more you fart” – but there has been little evidence to back it up, until now.
The researchers, led by Claudia Barber at the Liver and Digestive Diseases Networking Biomedical Research Centre in Barcelona, Spain, did a deep dive into the effects of diet on the gut microbiome and found that a largely plant-based diet can create a plant-paradise for “good” gut bacteria. Albeit with some stinky side effects. Their findings are published in the journal Nutrients.
The participants, 18 healthy men aged 18 to 38, were randomly assigned a diet – Western or fiber-enriched Mediterranean – to follow for two weeks. After a short break, they then followed the other diet for another two weeks. The fiber-enriched diet largely consisted of fruits, vegetables, and legumes.
Over the eight-week duration of the study, the team found that flatulence increased in volume and frequency in those on the fiber-enriched diet. The size of stools, which had a softer consistency, also increased, but the number of daily bowel movements stayed the same.
The men on the plant-enriched diet farted, on average, seven times more per day than those on the Western diet, according to logs they were required to keep. Each fart contained almost twice as much gas, measured using a balloon catheter fitted to the rectum after a meal of stewed beans.
Meanwhile, their poop – collected and weighed by the men themselves – was roughly twice the size while they were on the plant diet. About 200 grams (7 ounces) per day, compared to just 100 grams (3.5 ounces) while on the Western diet.
Eating more plants, and therefore fiber, promotes certain bacteria that use it as a food source. These extra bacteria are responsible for the increased stool weight, alongside water and a little undigested plant fiber, nutritionist Rosemary Stanton at the University of New South Wales in Sydney, Australia, told New Scientist.
The study indeed found that certain bacteria were more abundant in the men's guts following the plant diet. These included Anaerostipes hadrus and Agathobaculum butyriciproducens.
Fiber-fermenting bacteria break down fiber into short-chain fatty acids, which have many health benefits. They can reduce the risk of colorectal cancer, for example, prevent harmful bacteria from growing in the intestines, and protect against cardiovascular disease. It is for these reasons that they are known as “good bacteria”, and according to Stanton should be encouraged.
“Our Western idea that farting is a sign of something being wrong is totally false,” she said. In most cases, “farting is a sign of a healthy diet and a healthy colon.”