Excessive Gas in the Upper Gut (Stomach, Intestinal) Causes

Excessive gas in the stomach or intestines may present with a number of signs and symptoms. Some of these symptoms arise as a result of a higher than normal gas content in the gut and other symptoms occur due to the causes of excessive gas.

The gut contains about 200 milliliters of gas. Most of the gas in the upper gut is passed out with belching but some of the gas may pass further down the gut where it is expelled as flatus. Gas passed out from the upper gut as a belch is similar in chemical composition to air.

Most of the gas that is present in the upper gut is a consequence of air swallowing (aerophagia) when eating and drinking. Another common cause is the ingestion of carbonated beverages (fizzy sodas, beer) which is widespread in the modern diet.  Chemical digestion (action of digestive enzymes) and stomach and intestinal bacteria also produce moderate amounts of gas.

Symptoms of Excessive Gas in the Upper Gut

The main symptoms associated with excessive gas is :

Other symptoms may be due to large volumes of gas or is linked to one of the causes of excessive gas. This includes :

  • Stomach cramps or intestinal cramps – stretching of the wall of the gut due to the gas may cause a reflex contraction and spasm of the smooth muscle in the gut wall.
  • Stomach ache or abdominal pain – distension of the gut wall may elicit pain especially if gas pockets build up and trapped gas accumulates between solid matter in the gut or as a result of stomach/intestinal contractions.
  • Stomach noises or abdominal rumbling as gas moves through the gut and motility contractions mixes and moves the solid, liquid and gas contents in the gut.

Causes of Excessive Gas in the Upper Gut

The most common cause of gas in the esophagus, stomach, and duodenum is due to air swallowing (aerophagia) and the consumption of carbonated beverages.

Certain ‘gassy’ foods may increase gas in the gut but generally contributes to excessive flatus often as a result of the action of coliform bacteria. This is discussed further under Gassy Stomach.


  • Air swallowing (aerophagia) occurs for various reasons including eating or drinking too quickly, mouth breathing, hyperventilation (anxiety), excessive gum or tobacco chewing and poorly fitted dentures.
  • Air is trapped usually in the upper esophagus but may pass down into the stomach and duodenum. It is usually passed out as a belch but can extend further down into the lower gut where it is passed out with flatus.

H.pylori Infection

  • Invasion of the gastric and duodenal mucosa by Helicobacter pylori bacteria does produce moderate amounts of gas due to the chemical process that occurs when the bacteria protects itself from the stomach acid.
  • While the amounts of gas produced in this case is very small, it may partly contribute to excessive gas in the stomach.

Hiatal Hernia

  • Protrusion of a portion of the stomach through the diaphragmatic opening into the chest cavity can cause a host of upper GI symptoms.
  • A hiatal hernia does not cause gas production but decreases the stomach volume and may affect digestion and cause a stomach bloating with additional symptoms like excessive belching.

Delayed Gastric Emptying

  • This may be due to muscle and/or nerve dysfunction like gastroparesis, hormonal disturbance (digestive hormones) or a physical obstruction like in pyloric stenosis, stomach polyp or other stomach and duodenal tumors.
  • Food stays in the stomach for a longer period than normal and this increases the gas production as a result of gas digestion plus any bacteria, like with H.pylori infection, have a longer time span to consume the food.

Food Intolerances

Small Intestinal Bacterial Overgrowth

  • Overgrowth of normal intestinal flora (normal gut bacteria) in the small intestine consumes nutrients in the ingested food thereby releasing gas as a byproduct.
  • Small intestinal bacterial overgrowth (SIBO) ‘robs’ the body of essential nutrients and impairs digestion and absorption thereby leading to malabsorption syndromes.

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