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What Is Gas and What Is Bloating?

author image Russell Havranek, M.D.
Dr. Havranek completed his undergraduate studies and medical school at the University of Nebraska. He then completed his residency in internal medicine and fellowship in gastroenterology at the University of Texas Health Science Center in San Antonio, Texas. He is board certified in gastroenterology and is the current President and CEO of Gastroenterology Clinic of San Antonio.
Whatever the overriding symptoms, having gas is uncomfortable at the very least.
Whatever the overriding symptoms, having gas is uncomfortable at the very least. Photo Credit Getty Images

Gas and bloating are the most common problems that bring people to the gastroenterologist. They affect all ages and genders. They cause embarrassment and discomfort. Gas and bloating come in many forms. Some people belch a lot. Some people feel they pass excess flatus. Some just feel big and bloated and uncomfortable. Whatever the overriding symptoms, having gas is uncomfortable at the very least.

What is Gas?

Gas is nothing more than air in the digestive tract. Bloating is the subjective feeling that the abdomen is full. Many people describe it as feeling like they have a balloon in their abdomen. When it has a visible increase in girth, we call it distention. Our digestive tract is made of the tubes that extend from our mouth to our anus. Most all gas production happens just past the stomach in the small intestine (about 18 to 22 feet long) and the large intestine, also known as the colon (about five to six feet long).

The main gases that exist in our gastrointestinal tract are carbon dioxide, oxygen, nitrogen, hydrogen and methane. There are two main reasons people have problems with gas and bloating — excess gas production and visceral hypersensitivity.

Excess Gas Production

Gas is a natural byproduct of the work done in our gastrointestinal tract as we digest food and move our stool. Everyone has gas. The amount of gas produced in the body depends upon one’s diet and other individual factors. The average amount of gas we normally produce has a wide range of somewhere between 500 milliliters and 1,500 milliliters in a day. However, some people do produce more gas than others.

Interestingly, we as humans don’t really make gas, it is mainly produced by the trillions of microorganisms (bacteria) that normally live in our bowels. In people that have more gas than normal, the gas builds up in their bowels and causes the symptoms of bloating, belching and passing of flatus. There are many reasons why people produce excess gas.

Visceral Hypersensitivity

Visceral hypersensitivity, a fancy medical term for sensitive bowels, is an interesting topic. There are many conditions that cause sensitive bowels, the most common of which is irritable bowel syndrome (IBS). We have found that most people that complain of gas and bloating actually aren’t making excess gas. What they have is visceral hypersensitivity, and their bowels are wired much more sensitively than others. They make normal amounts of gas in their bowels that the average person wouldn’t feel or notice, but because their bowels are more sensitive to things inside them they feel very gassy and bloated.

There have been several studies done on this topic. One of the most largely quoted studies measured gas excretion in patients with visceral hypersensitivity and bloating and showed that total gas excreted was not different than in healthy controls.


Whether you have excess amounts of gas in your gastrointestinal tract or normal amounts that just bother you too much, you are suffering from gas and bloating, and there are things we can do to help.

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