Gas within the upper gastrointestinal tract is a result of many factors including gas produced by :

  • Bacteria in the gut (normal and pathogenic bacteria).
  • Digestion and decomposition of food.
  • Air swallowing (aerophagia).
  • Carbonated drinks and effervescent solutions.

These causes may be a result of normal activity within the upper gastrointestinal tract (esophagus, stomach, duodenum), voluntarily induced or it may be due to a number of conditions and diseases. The most common symptom of increased gas in the upper gastrointestinal tract is excessive belching (burping) and bloating. Other symptoms referred to as indigestion may also be present. Refer to Severe Indigestion Causes and Symptoms for more information.

How Does Gas Get Trapped/Produced in the Stomach?

It is difficult to isolate whether the gas is trapped or produced only in the stomach. Usually any cause of gas within the upper gastrointestinal tract is referred to as a ‘gassy stomach’. At times, gas may be produced lower down the gastrointestinal tract and travels back into the upper gastrointestinal tract.

The most common, innocuous cause of excessive gas in the upper gastrointestinal is air swallowing (aerophagia).

  • The air travels down the esophagus and may enter the stomach or continue through to the duodenum. It usually stays in the esophagus and is passed out as a burp.
  • If it continues through to the stomach or intestine, it may build up for a while where it causes other symptoms like stomach or intestinal cramps and abdominal bloating.
  • Once the pressure builds up in the stomach or duodenum, the air can then force its way up the gut and passes out as a burp.
  • Less frequently the air may travel further down the gastrointestinal tract, into the latter parts of the small intestine, through to the colon and is passed out as flatulence.

Carbonated and fermented drinks are another common cause and in this case the gas quickly passes into the stomach from where it then travels up the esophagus and is passed out as a burp.

The most common pathogenic cause of a gassy stomach is due to H.pylori infection of the stomach and first part of the intestine. This bacteria, Helicobacter pylori, has an affinity for the stomach lining. It produces a number of substances that neutralize the protective mucus lining of the stomach. This allows stomach acid to cause irritation of the stomach lining (gastritis) or the development of stomach ulcers. As part of its mechanism of action to shield itself from the gastric acid, H.pylori is able to neutralize the acid around it and in the process of doing so, it produces gases like hydrogen and carbon dioxide.

Causes of a Gassy Stomach

Gassy Foods

Certain foods are more ‘gassy’ than others. These foods usually have a high carbohydrate (starch, raffinose, lactose, fructose, sorbitol), sulphur (sulfur) and/or fiber content.

While gassy foods are more responsible for gas build up in the lower gastrointestinal tract (large intestine) where the gas is passed out as flatulence, it may also contribute to gas production in the upper gastrointestinal tract.
Gassy foods do not affect every person by causing gas buildup, excessive belching, bloating and flatulence. Some people are more prone to gas production due to the presence of large populations of certain bacteria in the gut, intolerances or impaired digestive processes.

Some of these gassy foods include :

  • Apples
  • Artificially sweetened foods
  • Asparagus
  • Beans
  • Broccoli
  • Brussel sprouts
  • Cabbage
  • Cauliflower
  • Corn
  • Garlic
  • Leeks
  • Lentils
  • Onions
  • Pasta
  • Pear
  • Potato
  • Prunes
  • Wheat bran
  • Other whole grains

Food Intolerance and Malabsorption

Intolerances and malabsorption may be linked to the ‘gassy’ foods mentioned above. The more common of these are due to :

  • Lactose
  • Gluten
  • Fructose
  • Sorbitol

Refer to the following articles for more information on :

  1. Lactose Intolerance
  2. Gluten Intolerance
  3. Fructose Malabsorption
  4. Low FODMAP Diet
  5. Food High in Fructose, Sorbitol, FODMAPS

Carbonated drinks

  • Fizzy drinks or sodas have carbon dioxide bubbles to improve the flavor of the drink. Carbon dioxide isĀ  dissolved in the solution and slowly releases over a period of time.
  • Fermented beverages like beer have a high gas content due to the fermentation process.
  • Certain effervescent drinks for indigestion may increase gas production.
  • Alkalizing agents for kidney stones and UTI’s may also be responsible for gas production in the stomach.

Air Swallowing (Aerophagia)

Air swallowing is usually due to mouth breathing and may occur for the following reasons :

  • Nasal congestion
  • Eating or drinking too quickly
  • Cigarette smoking
  • Poorly fitted dentures
  • Hyperventilation (anxiety)
  • Chewing gum
  • Hypersalivation
  • Snoring and possibly the use of CPAP machines for sleep apnea

Gassy Stomach Diseases

Certain diseases may cause increased upper gastrointestinal gas or the excess gas may be a symptom of the disease.

  • Bile reflux
  • Eating disorders
  • Food poisoning
  • Gastric dumping
  • Gastritis
  • Gastroenteritis
  • Gastroparesis
  • Gastrointestinal obstruction
    • Tumor
    • Intussusception
  • Hiatal hernia
  • H.pylori infection
  • Irritable bowel sydrome (IBS)
  • Pancreatic insufficiency
  • Peptic ulcers
  • Pregnancy
  • Small intestinal bacterial overgrowth (SIBO)

Refer to the following articles for more information on the conditions mentioned above :

  1. Excessive Belching (burping) and Bloating
  2. Causes of Bloating and Gas
  3. Sulfur or Rotten Eggs Belching

Article reviewed by Dr. Greg. Last updated on June 14, 2010