Gas in the Digestive Tract

What is gas in the digestive tract?

Gas in the digestive tract is created from:

• Swallowing air

• The breakdown of certain foods by the bacteria present in the colon

Everyone has gas. It may be uncomfortable and embarrassing, but it is not life-threatening. Gas is eliminated by burping or passing it through the rectum. Most people produce about 1 to 4 pints of gas a day and pass gas about 14 times a day.

Most gas is made up of odorless vapors--carbon dioxide, oxygen, nitrogen, hydrogen, and sometimes methane. Bacteria in the large intestine release gases that contain sulfur and produce an unpleasant odor of flatulence.

What causes gas in the digestive tract?

Gas in the digestive tract comes from two sources:

• Aerophagia (air swallowing). This is usually caused by eating or drinking rapidly, chewing gum, smoking, or wearing loose dentures.

  Belching is the way most swallowed air leaves the stomach. The remaining gas is partially absorbed into the small intestine and a small amount goes into the large intestine and is released through the rectum.

• Breakdown of certain undigested foods by harmless bacteria naturally present in the large intestine (colon)
  
  Some carbohydrates (sugar, starches, and fiber) are not digested or absorbed in the small intestine because of a shortage or absence of certain enzymes. The undigested or unabsorbed food then passes into the large intestine, where harmless and normal bacteria break down the food. This process produces hydrogen, carbon dioxide, and, in about one-third of all people, methane gases, which are released through the rectum.

What are the symptoms of gas?

Chronic symptoms caused by too much gas or by a serious disease are rare. The following are the most common symptoms of gas. However, each individual may experience symptoms differently. Symptoms may include:

• Belching. Belching during or after meals is normal, but people who belch frequently may be swallowing too much air and releasing it before the air enters the stomach.

  Chronic belching may also indicate an upper GI disorder, such as peptic ulcer disease, gastroesophageal reflux disease (GERD), or gastritis.

  According to the NIDDK, rare, chronic gas syndromes associated with belching include the following:

  • Meganblase syndrome. Meganblase syndrome causes chronic belching. It is characterized by severe air swallowing and an enlarged bubble of gas in the stomach following heavy meals. Fullness and shortness of breath caused by this disorder may mimic a heart attack.

  • Gas-bloat syndrome. Gas-bloat syndrome may occur after surgery to correct GERD. The surgery creates a one-way valve between the esophagus and stomach that allows food and gas to enter the stomach.

• Flatulence. Passing gas through the rectum is called flatulence. Passing gas 14 to 23 times a day is considered normal.

• Abdominal bloating. Bloating is usually the result of an intestinal motility disorder, such as irritable bowel syndrome (IBS). Motility disorders are characterized by abnormal movements and contractions of intestinal muscles. These disorders may give a false sensation of bloating because of an increased sensitivity to gas.

  • Splenic-flexure syndrome is a chronic disorder that may be caused by gas trapped at bends (flexures) in the colon.

  • Crohn's disease, colon cancer, or any disease that causes intestinal obstruction, may also cause abdominal bloating.

  • Internal hernias or adhesions (scar tissue) from surgery may cause bloating or pain.

  • Fatty foods can delay stomach emptying and cause bloating and discomfort, but not necessarily too much gas.

• Abdominal pain and discomfort. Gas in the intestine causes pain for some people. When it collects on the left side of the colon, the pain can be confused with heart disease. When it collects on the right side of the colon, the pain may feel like the pain associated with gallstones or appendicitis.