Why do people fart?

Hey Alice,

Why do people fart?

Dear Reader,

As the saying goes: everyone farts. In fact, on average, people pass gas approximately 15 to 20 times each day. The act of farting, or flatulence, may be a surprising, occasionally embarrassing, potentially stinky, and sometimes outright booming experience that many people would be more than happy to do without. Seriously, though, when it comes down to it, what's farting all about? For starters, the gas that makes up a fart comes from two sources: most of it originates from the breakdown of food in the digestive system, and the other bit is from swallowed air. Read on for more detail about what makes the farts flow!

In the first case, food particles that haven't broken down earlier in the digestive process are broken down by intestinal bacteria in the colon. Although microorganisms in the body consume most of the gas that's produced through this process, any remaining gas eventually leaves the body by way of farting. In the second case, air that a person swallows from eating, drinking, breathing, chewing gum, and smoking (among other ways of entry) that's not released by way of a burp or belch travels through the stomach and intestines. In either case, gas flows down through the rest of the digestive tract and eventually exits the body through the anus which is what causes the fart. Although embarrassing at times, this silent or noisy expulsion may help bring about some relief and comfort from a buildup of gas within the lower part of the body.

There are a number of foods known to cause or increase flatulence, including:

  • Cruciferous vegetables that contain raffinose, such as broccoli and Brussels sprouts
  • Food that has high fiber content, such as beans and lentils
  • Food that contains fructose, such as fruits, asparagus, and artichokes
  • Food that contains lactose, such as milk and cheese
  • Processed food products that contain sorbitol, such as sugar-free gum and candy  
  • Carbonated beverages

Adapted from the American College of Gastroenterology.

The foods listed are more difficult for the body to digest, and thus aren’t digested until they reach the colon. This means that once a gas-inducing food (such as broccoli) reaches the colon, it's then consumed by intestinal bacteria and produces gas, some of which is expelled by the anus.

Although it's a natural process, sometimes flatulence causes discomfort or stomach pain, which may be a sign that something in your digestive system has gone awry. Some digestive issues associated with gassy discomfort include:

  • Small intestinal bacteria growth
  • Irritable bowel syndrome (IBS)
  • Gastroesophageal reflux disease (GERD)
  • Problems digesting carbohydrates, including lactose intolerance, dietary fructose intolerance, or celiac disease 

Adapted from the National Institute of Diabetes and Digestive and Kidney Diseases (NIH).

There are ways to reduce gas pain, such as removing gas-producing foods from your diet, or chewing and swallowing food at a slower pace. However, if you find you’re experiencing gas-related discomfort that's getting in the way of your daily life, consider reaching out to a health care provider for guidance. 

Thank you for bringing this to our readers’ attention. Fart on!

Last updated Dec 27, 2019
Originally published Jun 01, 2001

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