What is flatulence?

Food passes from the stomach into the small intestine where enzymes break them down and they are absorbed into the bloodstream. Unabsorbed food then passes into the colon, and the bacteria in the colon break them down into waste products. In the colon, bacterial fermentation takes place and produces gas which is known as flatulence and is released through the anus (end of digestive tract). 

Sugars are carbohydrates that commonly cause gas production because of their ability to ferment. Fibre cannot be digested but it helps to regulate bowel movements and therefore keeps the digestive system healthy. 

Flatus is composed mainly of carbon dioxide and other gases like oxygen, nitrogen and hydrogen. The nasty smell associated with flatus is from sulphur-containing compounds that make up less than 1% of the gas. Red meats and other proteins contain more sulphur, hence causing your flatus to smell bad if you eat more of them. However, it may also signal other medical conditions such as internal intestinal bleeding and intestinal infections. 

What are the symptoms that accompany flatulence?

Passing wind is normal, but the amount of wind each person passes will vary and depends on the diet of the individual. Symptoms of excessive flatulence include: 

  • Passing wind often 
  • Smelly flatus 
  • Loud flatus  
  • Abdominal distension and discomfort 
  • Rumbling of the lower abdomen

Experiencing any of the symptoms above?

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What causes flatulence?

Small quantities of air can be swallowed along with food and liquid when we eat. The excess air passes along to the bowel for expulsion. “Air-swallowing” happens more often in those who are anxious. 

Stomach acid is neutralised by pancreatic secretions and carbon dioxide is produced as a by-product of this normal digestion process, creating gas that is released as flatus.

The bowel hosts many kinds of bacteria that help in digestion by fermenting some of the food components. The fermentation process produces gas as a by-product. Some of this gas is absorbed into the bloodstream and breathed out by the lungs, others is pushed along the bowel and expelled as flatus.

While fibre is important for the health of the digestive system, the small intestine can’t break down some types of fibre, which means extra work for gas-producing intestinal bacteria. High-fibre diets hence cause excessive gas production. 

Some people are unable to digest certain sugars found in cow’s milk. This means that bacteria will do the digestion through fermentation instead, which produces gas in the process, leading to flatus. 

Some people may not be able to digest certain short-chain carbohydrates such as fructose, present in foods like honey, corn syrup and some fruits. These are known as FODMAPS – fermentable oligo-, di-, monosaccharides and polyols. Fermentation of FODMAPS releases excess gas as flatus. 

What conditions are associated with flatulence?

A healthy individual may pass flatus about 8 – 20 times in a day. So, flatus is a completely normal bodily function, unless it is excessive. Excessive flatulence may be caused by lactose intolerance. Sometimes, it is because of fructose intolerance or small intestine bacterial overgrowth. 

Excessive flatulence may be associated with the following conditions:

Undigested food that remains in the colon has more time to ferment and release more flatus. 

Lactose intolerance, gluten intolerance and celiac disease may affect the digestion and absorption of food components, causing excessive amounts of these components present for fermentation to occur. 

Eating or drinking too quickly may cause more gas to enter the digestive tract. 

Bacteria in the small intestine may overgrow and produce more gas, adding on to the gas already produced by the colon. 

These introduce gases into the digestive tract. 

People with high stress or anxiety may experience irritable bowel syndrome where they fart excessively. Stress and anxiety induce the “fight or flight” response and this causes the brain to temporarily inhibit digestion, leading to problems like flatulence. 

What are the treatments for flatulence?

There are over-the-counter (OTC) medications like charcoal pills that can absorb gas in the gut, reducing flatulence. However, charcoal pills may interfere with the effectiveness of other medications by absorbing their active ingredients. 

Looking for a treatment?

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What foods should I avoid for flatulence?


Some foods containing dietary sugars include:

  • Beans 
  • Milk and dietary products 
  • Onions, artichokes and wheat 
  • Sugar-free foods using artificial sweeteners like sorbitol 


Some foods high in starch include: 

  • Potatoes 
  • Corn 
  • Wheat 


Fibre can help in digestion but a sudden increase in fibre consumption can cause gas and bloating. Soluble fibre produces the greatest amount of gas. 

Some foods high in soluble fibre include: 

  • Oat bran
  • Peas 
  • Fruits 

To help digest fibre, drink plenty of water. You do not have to completely avoid these foods, but consume them in moderation and keep away from trigger foods if you find any.

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