Men fart more when eating a plant-based diet due to good gut bacteria

Good gut bacteria is promoted by plant-based foods Shutterstock / Megan Betteridge
Researchers have discovered that men who eat plant-based diets tend to fart more and to have larger stools. However, this seems to be a positive thing as these foods promote healthy gut bacteria.

It is known that more vegetables, fruits, and legumes can make stools bulkier and increase flatulence. These changes have not been measured or linked to gut bacteria in any studies.

Claudia Barber, from the Liver and Digestive Diseases Networking Biomedical Research Centre, Barcelona, Spain and her colleagues compared the effects on the stomachs of 18 healthy men between 18 and 38 years old of a Mediterranean-style diet that was mostly made up of plants to a Western-style diet with fewer fruits and vegetables. After two weeks of following one diet, each participant was randomly assigned to another diet. Then, after a break they switched to the other diet.


While the men had the same number of poos each day on both diets, they produced about twice as many stools while on the plant diet. The men weighed their stools with digital scales. They found that they produced 200 grams per day when on the plant diet.

Rosemary Stanton, a University of New South Wales researcher in Sydney, Australia, says that eating plants encourages certain bacteria in our stomachs to make food by fermenting plant fiber. She explains that the stool weight increases are made up of the waste bodies of these bacteria and water, along with a small amount undigested plant fibre.

An analysis of their waste revealed that some of the fibre-fermenting bacteria found in men's guts increased while they were eating a plant diet, including Agathobaculumandanaerostipes.

Participants kept track of how often they farted each day with a handheld counter. They found that they farted seven times as much on the plant diet as they did on the Western diet. The men farted approximately 50 percent more gas than the average meal. Researchers gave them a test meal with stewed beans. They then measured the subsequent gas production by fitting balloons to their rectums.

Stanton says eating plants encourages farting. Most fart gas is odourless hydrogen methane, carbon dioxide, and methane that are produced by bacteria in the gut when they ferment plant fiber. Farts smell because of traces of hydrogen sulfur gas, which is a byproduct of protein digestion.

Because they release short-chain fat acids, fibre-fermenting bacteria is known as "good bacteria". These chemicals protect the large intestine from bowel cancer and keep it healthy. These short-chain fatty acid can be absorbed into bloodstreams, where they help prevent heart disease and diabetes.

Stanton says that flatulence caused by eating more plants is something to be encouraged. She says that the Western notion that farting means something is wrong is completely false. She says that farting is usually a sign of a healthy diet, and a healthy colon.

Journal reference: Nutrients, DOI:

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