Flatulence

Gas can build up in your tummy.

This gas comes from air you swallow. It also comes from tiny living things in your gut. These tiny things break down your food. This makes gas as they work.

Muscles push the gas out of your body. This can make a sound. It can also have a bad smell.

Some foods like beans make more gas. This is a normal part of being healthy. It is best to let the gas out.

Passing gas is a normal part of being healthy. Doctors call this gas flatus. Most of it is made in your gut.

Gas comes from a few different ways. You might swallow air while eating or drinking. This is called aerophagia. Most gas comes from fermentation. This is a way that tiny living things in your gut break down food. These tiny things are called microbiota. They live mostly in your colon.

Some foods make more gas than others. Foods like beans and lentils have special sugars. These sugars are hard for your body to digest. Instead, they go to your colon. There, the bacteria ferment them. This makes a lot of gas.

Most of the gas has no smell. It is made of things like nitrogen and oxygen. Less than one percent of the gas causes a bad odor. This smell comes from sulfur compounds. Muscles in your body push the gas out. This can make a sound.

It is not healthy to hold gas in for a long time. Sometimes, too much gas can cause pain or bloating.

Passing gas is a normal part of how our bodies work. Doctors use the word flatus to describe the gas in our stomach or bowels. This gas is pushed to the rectum by muscles in the intestines. Eventually, the gas is expelled through the anus. This is commonly called farting. People use many names for this, like "breaking wind" or "tooting."

Many societies have rules or taboos about it. Because of this, people might try to be quiet or hold it in. However, scientists say it is not healthy to hold gas in for long periods.

Gas comes from a few different sources in the body. Some of it is swallowed air, which is called aerophagia. This happens when we eat or drink. Other gases are made inside the gut through fermentation. This is a process where tiny living things break down food. Most of this gas is made in the colon. In a normal person, about 74 percent of flatus is made this way.

This gas is mostly made of odorless things like nitrogen and oxygen. It also contains hydrogen, carbon dioxide, and methane.

What we eat is the main reason we make gas. Some foods have special sugars called oligosaccharides. These are hard for humans to digest. They pass into the colon where bacteria ferment them. This creates a lot of gas. Common foods that do this include beans, lentils, and onions. Other foods like broccoli or cabbage can make the gas smell stronger. Some people also make more gas if they have certain health issues. These can include lactose intolerance or celiac disease.

Most of the gas has no smell at all. Less than 1 percent of the gas causes an odor. This smell comes from volatile sulfur compounds. One of these is called hydrogen sulfide. Scientists found that the amount of hydrogen sulfide helps decide how bad the smell is. The sound of passing gas is made by the anus and buttocks. This works much like a musical embouchure.

While gas can be funny, it can also cause embarrassment or annoyance.

People have studied gas for a long time. Scientists became very interested in it during high-altitude flights and space travel. They wanted to know how low pressure and small spaces would affect people. Even more than 200 years ago, people recorded gas issues in mountaineers. There is even a scientific study of this topic called flatology. In a normal day, a person might pass between 476 and 1,491 mL of gas. Understanding how our bodies use gas helps us learn about our health.

Flatulence is the medical term for the expulsion of gas from the intestines through the anus. This process is commonly known as farting. The gas itself is referred to as flatus. Flatulence is a normal part of human biology. It occurs when gas is brought to the rectum and pressurized by intestinal muscles. The scientific study of this biological process is called flatology. While many societies treat the subject as a taboo, scientists suggest that holding flatus in for long periods is not healthy.

Gas enters the digestive system from two primary sources: exogenous and endogenous. Exogenous gases are those that come from outside the body. This often happens through aerophagia, which is the excessive swallowing of environmental air while eating or drinking. This swallowed air is often emitted from the mouth through eructation, or burping. Endogenous gases are produced internally within the gastrointestinal tract. These gases result from the fermentation of food residues by microorganisms. In a healthy person, endogenous gases make up approximately 74 percent of the total flatus volume.

The mechanism of gas production relies heavily on the intestinal microbiota. The highest concentration of these bacteria is found in the colon. The small intestine is typically nearly sterile. When unabsorbed food residues arrive in the colon, they undergo fermentation. This process is driven by bacteria and microorganisms like yeast or prokaryotes. For example, certain complex carbohydrates called oligosaccharides are difficult for mammals to digest. These pass through the small intestine unchanged. Once they reach the colon, microorganisms like the archaea Methanobrevibacter smithii ferment them. This biological activity produces copious amounts of gas.

Diet is the most significant factor in determining how much gas a person produces. Foods high in certain polysaccharides, specifically oligosaccharides like inulin, are major contributors. Common examples include beans, lentils, onions, garlic, and various vegetables like sweet potatoes and turnips. Cruciferous vegetables, such as broccoli, cabbage, and cauliflower, are also known to increase the volume of flatus. Some of these foods may also increase the pungency, or strength, of the odor. A person's unique microbiota composition also plays a role in how much gas is produced.

Most flatus is actually odorless. Over 99 percent of the volume consists of gases like nitrogen, oxygen, carbon dioxide, hydrogen, and methane. Nitrogen is not produced by the gut but is swallowed from the air. Hydrogen and methane are flammable gases produced during fermentation. Not all humans produce methane, as it depends on the presence of specific archaea. The characteristic odor of flatulence comes from less than 1 percent of the total volume. This smell is caused by volatile sulfur compounds. Hydrogen sulfide is a major contributor, and its concentration often correlates with how strong the odor is perceived to be. Other compounds include methyl mercaptan and dimethyl sulfide.

Gas can also cause physical symptoms beyond simple expulsion. Some people experience bloating or abdominal distension, which is an increase in abdominal girth. This is often caused by abnormal intestinal gas dynamics rather than just high gas volume. In these cases, gas may undergo segmental pooling or focal distension in the intestines. Other symptoms include pain, excessive odor, or gas incontinence. Gas incontinence is a loss of voluntary control over passing flatus. It is considered a subtype of faecal incontinence. In some cases, excessive or malodorous gas can signal health disorders like celiac disease, lactose intolerance, or irritable bowel syndrome.

Human interest in flatulence has grown alongside advancements in travel. Scientists became particularly interested in the subject during the rise of high-altitude flight and human spaceflight. They needed to understand how low atmospheric pressure and confined spaces would affect the body. Even before modern flight, the phenomenon of gas expulsion in mountaineers was recorded over 200 years ago. The social impact of flatulence is also significant. The noise is produced by the anus and buttocks working together, similar to a musical embouchure.

This can lead to various social reactions, ranging from amusement to embarrassment.