Why We Pass Gas

Farting is usually a result of digestion, while burping is due to swallowed air

Everyone passes gas, better known as farting or belching. Gas in the digestive system is either swallowed air (e.g., from talking while eating) or produced by bacteria inside the body during digestion. While undesirable, occasional passing of gas is completely normal.

Woman burping while eating

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Most people have a certain amount of control over how much gas they pass. Altering your diet can reduce gas so you burp and fart less. But there's always going to be some that needs to be released.

This is actually a good thing. It means, in part, that your digestive system is doing what it is supposed to do—breaking down foods into the vitamins and minerals that the body needs.

This article discusses why we pass gas and the pain that can be associated with it.

Swallowed Air

Gas that is found in the stomach can come from swallowing air (aerophagia). Some air is naturally swallowed while:

  • Talking
  • Eating
  • Drinking carbonated drinks like soda
  • Chewing gum, which can cause even more air to enter into the esophagus and potentially go down into the stomach

Much of this gas is released the way it came in—through the mouth, as belching. But some does travel through to the stomach and beyond.

Most of this gas is absorbed on its way through the intestines, but some may become flatulence and leave the body through the rectum.

Byproduct of Digestion

A fart is a byproduct of food that does not get broken down completely in the small intestine.

Enzymes and bacteria that do the work of digesting food are present in the gastrointestinal tract. Some foods cannot be broken down fully by the enzymes in the small intestine, so they get passed into the large intestine.

The large intestine contains a number of different forms of bacteria that continue the digestive process, but this process creates carbon dioxide and hydrogen. About a third of people also have methane in their flatulence.

These gases need to leave the body and do so by passing through the rectum as farts.

What's in the Gas We Pass?

The main components of gas include carbon dioxide, oxygen, nitrogen, and hydrogen. These gases do not give off an odor. However, the gas that comes from the rectum may also include sulfur-containing compounds, which do have an unpleasant scent. Methane can also be present in gas, but it's not typical.

Pain or Discomfort From Gas

Some people may have gas in the digestive tract that causes them discomfort, such as abdominal bloating or distention.

This can lead to a desire to make changes to your diet or lifestyle in order to have less gas.

Keep in mind that everyone has gas and must pass it several times a day. If you feel you have an excessive amount of gas or it is causing a disproportionate amount of pain, you should talk to your healthcare provider.


Individuals pass gas, or fart and belch, for many reasons including swallowing air and as a byproduct of the digestive process.

Gas in the stomach tends to be released through belching, although it can also lead to farts. Gas in the intestines tends to leave the body as flatulence. For some individuals, gas can lead to pain and discomfort.

A Word From Verywell

Most people don't actually have too much gas, even though it can seem that way at times. Making some changes in diet and lifestyle can often help, but if bloating is still excessive or unrelenting, consult with your healthcare provider.

Frequently Asked Questions

  • How often do most people fart and burp?

    On average, most people belch up to 30 times a day and may fart between eight to 25 times a day.

  • Do you fart more as you get older?

    While research on this is limited, you may pass gas more as you age. One reason for this is that being older means you are at increased risk intestinal bacteria overgrowth, which fuels gas production.

  • Why do we pass gas in our sleep?

    Gas may build up in your body during the day. While you sleep, your body is relaxed. Any remaining gas in your digestive tract can easily be released.

  • Does eating less cause gas?

    Eating less, along with other eating and drinking habits, can lead to an increase in gas. However, everyone is unique and may become gassy for different reasons.

  • What happens when you hold in a fart?

    Holding in a fart can feel uncomfortable and lead to stomach pain, bloating, and distension, which is when your belly becomes larger than normal.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American College of Gastroenterology. Belching, bloating, and flatulence.

  2. Cleveland Clinic. Gas.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and causes of gas in the digestive tract.

  4. Almario CV, Almario AA, Cunningham ME, Fouladian J, Spiegel BMR. Old farts – fact or fiction? Results from a population-based survey of 16,000 americans examining the association between age and flatusClinical Gastroenterology and Hepatology. 2017;15(8):1308-1310. doi:10.1016/j.cgh.2017.03.023

  5. Canadian Society of Intestinal Research. Intestinal gas.

  6. National Institute of Diabetes and Digestive and Kidney Diseases. Eating, diet, and nutrition for gas in the digestive tract.

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.