Why do we fart?

As a gastroenterologist with a keen interest in the intricacies of the human digestive system, I often find myself explaining the natural bodily function of flatulence, commonly known as farting. It's a topic that can be both humorous and informative, shedding light on the complex processes that occur within our bodies every day.
The human digestive system is a marvel of biological engineering, designed to break down food and absorb nutrients. However, this process isn't 100% efficient, and a byproduct of digestion is the production of gases. These gases are a mixture of various elements, including oxygen, nitrogen, hydrogen, carbon dioxide, and methane, among others. The presence of these gases in the digestive system is completely normal and is a result of both the food we eat and the bacteria that inhabit our intestines.
When we consume food, our body begins to break it down in the stomach through a process called mechanical digestion, where food is physically broken into smaller pieces, and chemical digestion, where enzymes and acids break down the food chemically. As food moves through the small intestine, it is further broken down, and nutrients are absorbed into the bloodstream. However, not all food can be broken down and absorbed. The undigested food particles then move into the large intestine, or colon.
The large intestine plays a crucial role in the process of flatulence. It houses a diverse population of bacteria, collectively known as gut microbiota. These bacteria help to break down the remaining undigested food particles through a process called fermentation. During fermentation, the bacteria produce various gases as a byproduct. This is one of the primary sources of the gas that eventually gets expelled as a fart.
Another source of gas in the digestive system comes from the act of eating and drinking. When we swallow, we also swallow air, which can contribute to the gas in our stomach. Additionally, some carbonated beverages and certain types of foods can introduce gas directly into the digestive system.
The composition of gas in a fart is largely odorless, with nitrogen making up about 20%-90% of the total volume, followed by oxygen, carbon dioxide, hydrogen, and methane. However, the smell associated with farts is caused by trace amounts of other compounds.
Hydrogen sulfide and ammonia are two such compounds that can give farts their characteristic smell. Hydrogen sulfide has a rotten egg smell, while ammonia has a strong, pungent odor. The presence and concentration of these compounds can vary greatly depending on an individual's diet and gut microbiota.
It's important to note that while flatulence can be embarrassing in social situations, it is a completely natural and necessary bodily function. It serves as a means for the body to expel excess gas and maintain the balance of the gut environment. Suppressing the urge to pass gas can lead to discomfort and, in some cases, more serious health issues such as bloating, abdominal pain, and even hernia.
In conclusion, farting is a normal part of the digestive process and is essential for maintaining the health of our gastrointestinal system. Understanding the science behind it can help alleviate some of the social stigma associated with this natural bodily function. It's a reminder of the fascinating and complex processes that are constantly at work within our bodies, keeping us alive and healthy.

A fart, also called gas, --passing wind-- or flatulence, is caused by the internal buildup of gases that are formed during the process of digestion and respiration. The causes of farts and how they develop within the digestive tract vary considerably depending on the person and circumstance.Feb 9, 2016