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What Causes Gas and Bloating in the Stomach? - The Different Culprits

Medically reviewed by Mia Dacumos, MD · Nephrology · Makati Medical Center

Written by Tracey Romero · Updated Dec 14, 2020

What Causes Gas and Bloating in the Stomach? - The Different Culprits

The build-up of excessive amounts of gas in the gastrointestinal tract may lead to abdominal bloating, which is defined as a subjective feeling of upper abdominal fullness or discomfort, associated with gas. But what causes gas and bloating in the stomach?

The actual physical finding of a “bloated abdomen” is termed abdominal distention. The feeling of bloating may not always be associated with the physical finding of abdominal distention. However these two may be seen hand-in-hand in patients. In fact, some studies state that only half of the patients who present with abdominal bloating had concomitant abdominal distention.

The Best and Worst Foods for Bloating

What causes gas and bloating in the stomach?

There are several possible causes for abdominal bloating, most commonly this is constipation. However, several conditions may also cause abdominal bloating, which influences intestinal gas production and its transit throughout the intestines.

Listed below are general causes of abdominal bloating and how it may lead to bloating.

  • Small Intestinal Bacterial Overgrowth (SIBO) can manifest after intestinal surgery and/or IBS with subsequent diarrhea.
  • Hypersensitivity of the gut. Seen in patients with Irritable Bowel Syndrome (IBS), a group of symptoms that includes abdominal pain, diarrhea, constipation, or a mix of both. These patients are extremely sensitive to gas in the intestinal tract, which may lead to abdominal bloating.
  • Conditions causing gastroparesis. Refers to conditions that cause delayed gastric emptying. There are many conditions that may cause gastroparesis, which may be autoimmune, inflammatory, or neurologic in nature.
  • Gynecologic etiologies. Premenstrual Syndrome (PMS) or conditions of the ovaries/uterus may cause abdominal bloating.
  • Specific conditions causing abdominal bloating

    As mentioned earlier, bloating is caused by an excessive amount of gas in the gastrointestinal tract that is either due to overproduction or a problem in transit. Specific gastrointestinal conditions that may cause this are listed below.


    Since patients experiencing constipation will have a delayed transit time of intestinal contents, gas may build up causing abdominal bloating.

    Functional Dyspepsia (indigestion)

    A chronic disorder of sensation and gastrointestinal movement of the upper gastrointestinal tract.

    Intestinal Obstruction

    This can be caused by infections, congenital or acquired defects of the intestinal wall, or surgical interventions causing adhesions (such as appendectomies).

    Gastroesophageal Reflux Disease (GERD)

    A condition where acid stomach juices or food and fluids are regurgitated from the stomach to the esophagus.

    Lactose Intolerance

    Patients with lactose intolerance are deficient in lactase, an enzyme necessary in the digestion of lactose (a disaccharide found in milk, yogurt, and ice cream). Lactose is a fermentable, gas-producing substance in the stomach that, if left undigested in the intestines, is fermented by naturally occurring bacteria (the normal flora of the gastrointestinal tract) that produces gas and subsequent abdominal bloating.

    Celiac Disease

    This is a condition where the body is unable to break down gluten, a protein found in foods made with wheat, barley, rye, and triticale. The immune system reacts to gluten, creating toxins that destroy the villi in the small intestines, causing poor absorption of nutrients.

    H. pylori bacterial infection

    This predisposes patients to hyperacidity, ulcer formation, and gastroesophageal reflux, which as mentioned earlier, causes gas increased gas production.


    This is a condition seen most commonly in the elderly population, where there is an outpouching of the intestinal walls where stool can pile up. This may lead to intestinal obstruction and inflammation, which may also manifest as abdominal bloating.

    Parasitic Infection

    Specifically, giardiasis, hookworm infection, and amoebiasis are gastrointestinal parasites that can cause bloating. 

    Short Bowel Syndrome

    This is a condition seen in patients who have gone gastrointestinal resection, have birth defects/hereditary conditions (intestinal atresia), Crohn’s disease, or any condition causing a portion of the large or small intestine to not function properly, leading to poor absorption of nutrients.

    what causes gas and bloating in the stomach

    When to seek consultation

    Abdominal bloating alone may not be a cause for serious concern, if patients are constipated, increased intake of fiber and hydration may resolve their bloating.

    However, when abdominal bloating is accompanied by other symptoms such as uncontrolled/excessive vomiting, haematemesis (blood in the vomit), hematochezia/melena (blood in the stool), nausea, a loss of consciousness, uncontrolled diarrhea, or no bowel movement for three days, then patients should seek consultation immediately.

    The pattern at which abdominal bloating presents itself may be alarming for patients as well. If bloating is accompanied by painful sexual intercourse, painful bowel movements, or after every meal, patients should seek medical consultation.

    Seek medical help when there has been no bowel movement for several days or the patient has had no flatus for the past few days.

    Prevention of Abdominal Bloating

    Abdominal bloating that is due to diet or constipation can be prevented by diet modification and adequate hydration. 

    Patients should follow the low FODMAP diet, which stands for low Fermentable Oligosaccharide, Disaccharide, Monosaccharide, and Polyols. These carbohydrates are not always fully absorbed, and thus, can lead to gas production via the normal flora of the gut. Selectively removing certain food mentioned below and seeing whether symptoms resolve may help in diet modification to prevent future bloating episodes.

    • Monosaccharides such as fructose, which is found in apples, honey, pears
    • Disaccharides such as lactose, which is found in dairy products
    • Oligosaccharides such as maltose, which is found in wheat
    • Polyols are sugar alcohols found in chewing gum, candies, some fruits, and vegetables.

    Key Takeaways

    What causes gas and bloating in the stomach? Abdominal bloating is a condition caused by several factors. The list includes excessive gas production, poor transit of gas through the gastrointestinal tract, or abnormal absorption of nutrients within the gastrointestinal tract.

    Consultation with a physician should be made if the accompanying symptoms are severe. These symptoms include blood in the stool and vomit, or if the pattern of its occurrence is abnormal (associated with every meal, painful sex, or painful bowel movement). The condition can be prevented by avoiding certain food listed in the low FODMAP diet and increasing fluid intake.


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    Mia Dacumos, MD

    Nephrology · Makati Medical Center

    Written by Tracey Romero · Updated Dec 14, 2020

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