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Gas, Bloating and Flatus

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What is gas? What do you mean by the gas in the gut or digestive tract?

Gas in a simple sense is the air present inside the digestive tract ie. within the stomach and intestines.

What causes gas within the digestive tract?

The formation or collection of gas within the digestive tract occurs due to 2 main reasons:

• Swallowing of external air into the digestive tract: This occurs while eating, drinking, or smoking. The gases that are swallowed into the gut mainly consist of oxygen, nitrogen, and carbon dioxide.

• Production of gas by bacterias within the intestine: this occurs during the process of digestion of food in the large intestine. This mainly leads to the production of hydrogen gas and methane in some people. A small amount of other gases are also present like hydrogen sulfide that gives bad smell to the gas passed by anus- called fart/flatus/flatulence.

How common is gas? How much gas is considered normal?

The gas formation or collection occurs in each one of us. People release gas from the gut either through the mouth in the form of burp or through anus inform of flatus/fart. This is generally a normal thing to happen in the process of intake and digestion of food and only considered abnormal if it is in excess volume or associated with other symptoms.

About 0.5 to 1.5 liters of gas is produced within the intestine which is released in the form of flatus/fart about 13 to 21 times per day in an average person normally. Occasional burping during or after a meal is also considered normal.

However, most people who complain of excessive gas do not produce more gas than the average person. Instead, they are more aware of normal amounts of gas. On the other hand, certain foods and medical conditions can lead to excessive production of gas.

When the gut gas is considered abnormal or what are the symptoms of abnormal gut gas?

The following are the symptoms when the gas formation or collection indicates an abnormality or just excess formation:


Excessive burping: Burping/ belching occurs due to swallowing of a small amount of air or from gas released from carbonated drinks. A small amount of air is swallowed normally in all of us while eating or drinking. Burping occasionally, especially during or after meals, is normal. Excess burping usually occurs due to excessive swallowing of air.

Excess burping is usually seen in people who tend to swallow more air repeatedly while eating, smoking, or drinking with straws.


Farting/Passing gas: there can be significant variability in the quantity and frequency of passing gas amongst different individuals. Researches have found that passing gas around 13 to 21 or even up to 25 times in a day is normal. This can amount to 0.5 to 1.5 liters of gas passed. More gas is passed while asleep.

Bloating: Bloating is a feeling of fullness or tightness in the abdomen mostly occurring during or after meals. There can be associated with obvious distention of the abdomen.

Pain or feeling of discomfort in abdomen:  This may occur when the gas does not move through the intestines normally.

It is found that excessive gas in the gut is not clearly related to the production of these symptoms in many healthy people and is thought to be associated with hypersensitive intestine.

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What are the alarming symptoms that need medical attention? When to see the doctor?

If a person feels symptoms of gas along with the associated with following complaints, it may suggest some serious underlying condition. These alarming are as follows:

• Blood in stool

• Weight loss

• Sensation of gas in the chest or chest pain

• Change in frequency or consistency of stools

• Development of consultation or diarrhea

• Chronic pain in the abdomen

• Persistent vomiting or nausea

What are the causes of abnormal gut gas or gut gas associated with symptoms?


Excessive swallowing of air:

This can occur due to the following things:

• Individual factor: some people tend to swallow more air while eating or drinking. This can occur in people who eat or drink too fast.

• Drinking carbonated or fizzy drinks

• Smoking

• Chewing gum

• Sucking on hard candy

Stress or anxiety in some people leads to swallowing of more air. Some people even try to induce burping during stress.

• Excessive salivation may cause swallowing of excessive air which may be seen in GERD, ill-fitted dentures, side effects of some drugs, or nausea, etc.

Dietary factors:

The presence of carbohydrates in the diet that can’t be fully digested by the stomach or small intestine is the main component responsible for the production of gases in the gut. These carbohydrates pass into the large intestine, where the bacterias break them down, releasing gases within the intestine.

The following are the sources of carbohydrates that are not digested completely:

• Sugars: such as fructose, raffinose, and sorbitol, which some fruit and artificial sweeteners contain.

• Starches: such as corn, wheat, and potatoes.

• Fibers: soluble fibers present in fruits, nuts, and dried beans. Insoluble fibers present in wheat bran, root vegetables, etc.

The International Foundation for Functional Gastrointestinal Disorders (IFFGD) has found that food items that cause excessive gas or fart will not necessarily have the same result on a different person.

However, some foods are found to produce more intestinal gas like:

• Fruits like apples, peaches, and pears or fruit drinks

Milk and milk products like cheese, ice cream, or yogurt.

Foods rich in raffinose: Humans are unable to digest a sugar called raffinose found in some of the food items. The bacterias present in the gut try to break it down producing lots of gases. Raffinose is found in a good amount in whole grains, beans, sprouts, broccoli, cabbage, and asparagus.

• Foods and drinks rich in sulfur: Eating a lot of food items that are rich in sulfur can result in frequent and bad-smelling farts. These are onion, garlic, cauliflower, cabbage, and broccoli. Drinks like wine and beer, are also high in sulfur and can produce similar effects.

• Foods containing sugar alcohols: Sugar alcohols are commonly used to provide sweetness to processed “sugar-free” foods. This is not completely digested by the body resulting in gas.


Medical conditions:

• Overgrowth or replacement of bacteria in small intestine: small intestine normally has bacterias called as normal flora that helps in the digestion of food. When there is a change in the type of bacterias or overgrowth of bacterias within the small intestine it can cause excessive gas production, diarrhea, or weight loss.

IBS (Irritable Bowel Syndrome): affects how gas moves through the gut and increases the sensitivity towards the normal amount of gas within the gut.

GERD (Gastroesophageal reflux disease): results in backflow of stomach content into the esophagus. These people may burp a lot to relieve discomfort.

Lactose intolerance: people with lactose intolerance are not able to properly digest sugar present in milk called lactose. On intake of milk or milk products, they develop excessive gas, bloating, and or diarrhea.

• Fructose intolerance: individuals with fructose intolerance develop excessive gas, bloating, and or diarrhea on consuming a sugar called fructose found in fruits and honey.

Celiac disease: people with celiac disease are not able to digest a protein called gluten present in some cereals like wheat, barley and rye and some cosmetic products and lip balms. On consumptions of substances containing gluten they develop symptoms like excessive gas, bloating, and or diarrhea.


Medical conditions that affect the movement of gas through the intestines:


Adhesions in abdomen

Hernias involving gut

Dumping syndrome

Intestinal obstruction

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How gas and bloating is assessed by the doctors? 

Most people with gas and bloating do not need to have any tests and are diagnosed by medical history and examination.

However when there are associated symptoms like diarrhea, abdominal pain, weight loss, blood in the stool, anemia, fever, or nausea, or vomiting. These alarming signs could be due to more serious condition and require further diagnostic tests described later:


Medical history

For a medical history, your doctor will ask about

• Your symptoms

• Your eating habits

• Prescription and over-the-counter medicines you take

• Current and past medical conditions

Your doctor may ask you to keep a diary of the food you eat and when you tend to develop the symptoms. Your diary may show specific foods that are triggering these symptoms. Reviewing your diary may also help your doctor find out if you have more gas or are more sensitive to normal amounts of gas.

Physical exam

During a physical exam, your doctor may

• check for bloating in your abdomen

• use a stethoscope to listen to sounds within your abdomen

• tap on your abdomen to check for tenderness or pain


Tests may include:

1. Stool test for blood, fat, or parasite like giardia.

2. Hydrogen breath test: this is done to diagnose lactose intolerance. Here a person is made to drink lactose and the amount of hydrogen is calculated in the air expired by the person along with changes in his symptoms. The presence of an excess of hydrogen and worsening of symptoms suggest the diagnosis of lactose intolerance.

3. X-ray abdomen: to see for abnormal distention of small intestine.

4. Endoscopy or colonoscopy: done to see for any abnormality inside the stomach or large intestine. It uses an endoscope which is a thin tube with a camera and instruments attached to it. The doctor can also take tissue samples for the lab test to confirm the diagnosis eg: celiac disease.

4. Blood tests: to look for 3 antibodies common in celiac disease:

• Anti-tissue transglutaminase (tTG) antibodies

• Endomysial antibodies (EMA)

• Deamidated gliadin peptide (DGP) antibodies

Know more about antibody tests for celiac disease

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