Under normal conditions, most of the gases that form farts come from our mouths. Only 10% of these gases arise in the fermentation of food along our large intestine. The rest is nothing more than air that we accidentally swallow during food or even air bubbles present in saliva or carbonated drinks (soft drinks and beer, mainly). These gases travel throughout the digestive tract until they find the gases produced by the action of bacteria on food. Together, these gases reach the rectal ampulla – the last part of the digestive tract, which ends at the anus – and are compressed there until you open a breach for them to come out and foul the environment. This happens 12 to 25 times a day (you fart in your sleep, you know?), releasing a total of 1 to 1.5 liters of gas. And if you think that men fart more than women, you are sadly mistaken. Farts don’t choose sex, but women, in general, are more embarrassed to relieve their gas in public. Smell and sound don’t choose sex either. The smell depends on what you ate and the noise is a combination of factors. “It is a correlation between the release speed, the contraction of the sphincter (the valve that controls the opening and closing of the anus), local humidity and the amount of fat in the stool, which lubricates the digestive tract”, says gastroenterologist Luciana Camacho -Lobato, from the Federal University of São Paulo (Unifesp).
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– What are the most poisonous gases in the world?
– Why does the fart sometimes make a noise and sometimes not?
At full steam! Eating cabbage or not, you release at least 1 liter of gas every day
1. Throughout the day, while we talk, we chew gum and, especially, during meals, we accidentally swallow small portions of air. People who smoke, eat very greedily and talk while eating, swallow even more air. Also, carbonated drinks and saliva itself carry some air in small bubbles.
2. The swallowed air (about 80% nitrogen and 20% oxygen) passes through the pharynx, through the esophagus and reaches the stomach, where it forms a kind of gas chamber. Part of that air makes its way back and is expelled through the mouth: it’s belching. Another part is absorbed by the organism, and the rest goes through the digestive tract, along with the food.
3. The walls of the digestive tract absorb portions of gases that are of interest to our body, along with nutrients taken from food. In this process, some gas molecules are trapped in the walls and are not absorbed. Gas remedies work by removing these bubbles, which join the rest of the gases
4. Food is only attacked by bacteria in the large intestine. The acidity makes it impossible for them to live in other organs. The final part of the small intestine could even receive them (it is neither acidic nor alkaline) but the region is rich in defense cells, which destroy the bacteria that live there
5. In the large intestine, bacteria ferment food, producing various types of gases and compounds. Aerobic bacteria (which need oxygen) produce carbon dioxide and anaerobic bacteria, methane. In addition, depending on the food, they generate some compounds – sulfides, fatty acids and sulfur – which give the gases a smell, naturally odorless.
6. There are trillions of bacteria of different types in the large intestine. Some of them alone could harm us, but other bacteria prevent them from existing in exaggerated numbers. This balance is important: in addition to generating diseases, the imbalance generates exaggerated production of gases
7. The anus is like a ring, with a valve (called a sphincter) on each side. The one on the inside opens involuntarily when the rectal ampulla becomes full (with feces or gas). The outside one you control and can open a little bit by little bit. But when the gaseous pressure is very strong, there is no way: the noise is inevitable
The smell of fart depends on what you eat. Fermentation of certain foods produces malodorous substances that combine with odorless gases (nitrogen, carbon dioxide, oxygen, hydrogen and methane) and make a mixture smelly:
• Beans, like peas, chickpeas, cabbage and others, contain raffinose, a sugar that we cannot digest. Therefore, a large part of these foods is fermented, producing many gases.
• Protein fermentation generates sulfur and hydrogen and carbon sulfides. Fat generates fatty acids. This is why meat and eggs cause the smelliest farts.
• Dairy products cause a lot of gas in people who lack the enzyme that digests lactose, the milk sugar. In this case, the lactose reaches the large intestine intact.