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There is no lack of popular names for the gases that arise in the stomach or intestines, escape rectally and are commonly known as gas or flatulence. As diverse as the choice of terms is also the olfactory nuance of the Leibwinde (German term, outdated).

Scientists from Monash University in Melbourne have now found that digestion can be controlled in such a way that intestinal gases smell less unpleasant, reports the "New Scientist".

But first the basics: Most of the intestinal gases that humans produce during digestion are released into the bloodstream and exhaled through the lungs. What is left of it paves the way in the other direction as flatulence.

In their composition, flatulences consist of nitrogen, hydrogen, methane, carbon dioxide and sulfur compounds. The latter - and here in particular the hydrogen sulfide - cause foul-smelling winds, known to most as the smell of rotten eggs. It occurs because intestinal bacteria, when processing protein-rich foods, produce hydrogen sulfide.

Increased risk of colon cancer

In addition to embarrassing moments of noisy flatulence - which, incidentally, are caused by the vibration of the anal opening and depend on the tension of the sphincter, speed and volume of the flatulence - this gas containing hydrogen sulfide can also aggravate inflammatory bowel disease and increase the risk of colon cancer.

For this reason, the Australian scientist Chu Yao and her team have now analyzed how different foods influence the amount of hydrogen sulfide that is produced in the intestine.

To do this, the researchers examined the stool of seven healthy adults and added the amino acid cysteine ​​to the excretions. It has a high sulfur content and is found in protein-rich foods such as meat, eggs and dairy products. The result of the mixing process: the intestinal bacteria in the excretions produced seven times the amount of hydrogen sulfide. "That explains why bodybuilders who consume a lot of protein powder are known to have smelly gas," says Yao.

Strength reduces production

When the team then mixed the stool samples with slowly degradable carbohydrates, the hydrogen sulfide production dropped significantly. This group of carbohydrates goes through the small intestine without complete digestion and is only fermented by bacteria in the large intestine.

Starches, such as those found in potatoes, bananas, legumes and cereals, and fructans - a component of wheat, artichokes and asparagus - had a particularly positive effect, reducing hydrogen sulfide production by 75 percent.

The research was presented at the annual meeting of the Gastroenterological Society of Australia in Adelaide in the fall and contradicts the well-known advice that people with strong and odorous flatulence should eat less fiber. This actually reduces the frequency of flatulence, but increases the amount of hydrogen sulfide produced. Yao believes that more flatulence, if it is odorless, is what most people prefer.

Afraid of bad smells

Her team now wants to use healthy volunteers and people with inflammatory bowel disease to test whether the flatulence that reaches after rotten eggs actually decreases when the diet consists primarily of low-protein foods and carbohydrates.

Rosemary Stanton from the University of New South Wales in Australia has also researched in this area and summed up: "It is not the farts themselves that people worry about, but the smell that could arise." In her opinion, no one should go without fiber anymore and thus risk constipation just because they are afraid of odor-intensive flatulence. "There's no good reason for a confident farter to cut out fiber." (Bernadette Redl, 3.1.2017)