Excessive Flatulence – Composition of Flatus and Causes

About 1 to 2 liters of gas is formed in the human gut every day due to the chemical processes of digestion and bacterial fermentation. A large portion of this gas is expelled from the body. However, about 200mL of this gas remains within the gut. The gas formed within the colon, rectum, and the last part of the small intestine is passed out through the anus as flatus or fart.

A small amount of gas formed in the upper half of the gut can also find its way out through the flatus. However, the majority of gas entering or forming within the upper gut is released through the mouth via belching (burping). Flatulence refers to an accumulation of gas in the lower gut. Under normal conditions, a person may pass flatus 15 to 20 times in a day. The odor, volume and sound of the flatus varies on an individual basis. These characteristics of the flatus may vary even for a single individual through the course of the day.

What makes up flatus?

Most of the gas in the lower gut is formed by the action of bacteria that reside in the bowels. Most of the bacteria in the gut live within the large intestine. These bacteria act on the digested food and waste matter that passes through the colon. This process of microbial fermentation plays a critical role in the human digestive process. These bacteria produce the essential vitamin K, which our body requires. Also, the bacteria digest all the remaining carbohydrates in the food and waste matter, and release the nutrients for absorption.

Methane, carbon dioxide, and hydrogen are the three main gases that are produced as a result of bacterial fermentation in the bowel. A small amount of nitrogen also enters the gut from the bloodstream. Air from the upper gut that is not passed out with belching may then pass all the way down to the lower gut although these amounts are relatively small when compared to a belch. These gases are then released as flatus.

Symptoms of Excessive Flatulence

Excessive flatulence or excessive gas refers to a condition in which a person experiences more than the normal amount of gas formation in a day. The following signs and symptoms may accompany excessive flatulence:

  • Excessive belching: Belching or burping (technically referred to as eructation) refers to the act of expelling the gas in the upper gut through the mouth. Belching is a normal process that relieves the abdominal discomfort caused by accumulation of excessive gas in the stomach. Excessive flatulence may also be accompanied by excessive belching.
  • Abdominal distension or bloating: Abdominal bloating or distension refers to an increase in the girth of the abdomen due to accumulation of gas or fluid. A bloated abdomen looks swollen and is firm or hard to touch. Bloating is also accompanied by abdominal discomfort or pain. Excessive gas accumulation can cause both excessive flatulence and abdominal bloating.
  • Abdominal pain or cramps: Excessive gas accumulation in the gut leads to distension, which can cause pain or cramps in the abdominal region.

Causes of Excessive Flatulence

The most common process of gas accumulation in the gut is through the chemical processes of digestion and microbial fermentation. However, these are not the only sources of gas in the gut. Gas accumulation in the gut could also be a result of excessive air swallowing, consumption of carbonated beverages, and hyperventilation caused by anxiousness.

Read more on excessive gas.

Most of the gas accumulated in the upper gut through these routes is passed out by belching. A small fraction of the orally consumed gas may find its way into the flatus. Consumption of gassy foods (such as beans), high fiber diets and certain medications may cause both excessive flatulence and excessive belching. Apart from the non-pathological modes of gas accumulation in the gut, there are some pathological conditions that may cause excessive gas accumulation and flatulence.

Impaired digestion

A variety of problems with the normal digestive processes in the gut can cause excessive formation of gas and excessive flatulence. Digestive problems can arise due to deficiencies or inactivity of certain digestive enzymes. Due to inadequate digestion, undigested food accumulates and provides a large source of raw material for bacterial fermentation.

Excessive bacterial fermentation due to the presence of undigested food in the gut results in excessive gas production and flatulence. A variety of conditions are associated with impaired digestion in the gut. Examples include biliary stasis, pancreatic exocrine insufficiency, malabsorption of fructose and sorbitol, and intolerance to lactose and gluten in the diet.


Excessive gas in the gut could also be a result of gastrointestinal infections. A variety of gastrointestinal infections are characterized by digestive disturbances and excessive flatulence. Examples include gastroenteritis, food poisoning, pseudomembranous colitis, diverticulitis, and small intestinal bacterial overgrowth. Gastroenteritis (also known as stomach flu) is a common example of an infectious condition that can cause excessive flatulence along with other digestive problems.

Small intestinal bacterial overgrowth (commonly abbreviated as SIBO) refers to excessive growth of gut bacteria within the small intestine, which leads to chronic diarrhea and malabsorption along with other digestive problems. Gastrointestinal problems can also be caused by toxins released by pathogens. Food poisoning in an example of such a condition.

Treatment of gastrointestinal infections with antibiotics tends to kill a lot of the normal intestinal flora, leading to an imbalance in the natural flora of the gut. This could cause excessive flatulence and belching even after successful treatment of gastrointestinal infections. Pseudomembranous colitis (also known as antibiotic-associated diarrhea) is an example of such a condition.

Slow bowel motility

Delayed transit of food through the gut creates opportunities for bacterial fermentation processes that cause excessive gas production. Delayed transit could occur due to a variety of reasons, including obstruction (or pseudo-obstruction) of the gut lumen and disorders of gut motility. Examples of some conditions that cause delayed transit and excessive flatulence include constipation, block in small or large intestine, delayed gastric emptying and diverticulosis.

Functional digestive disorders

Excessive flatulence can also be caused by functional digestive disorders. The exact cause of functional digestive disorders is not known, since they do not present with any physical abnormalities within the gut. A common example of functional digestive disorder is the irritable bowel syndrome (commonly abbreviated as IBS).

There are two subtypes of irritable bowel syndrome: diarrhea-predominant, and constipation-predominant. The exact cause of excessive gas in irritable bowel syndrome is not clear. Impaired transit of gas through the gut may be a possible reason.

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