Causes of flatulence

There are three main causes of excessive flatulence:

  • swallowing more air than usual,
  • eating food that is difficult to digest, and
  • having an underlying health condition that affects your digestive system.

Swallowing air

While it is perfectly normal to swallow air during breathing and eating, it is easy to swallow a lot more air than usual without realising it. This can lead to symptoms of excessive flatulence.

Ways that an excess amount of air can be swallowed include:

  • chewing gum,
  • smoking,
  • sucking on pen tops, and
  • not chewing food slowly and thoroughly (swallowing large lumps of food will result in you swallowing more air).

Hot and fizzy drinks will also increase the amount of carbon dioxide in your stomach, although this is more likely to lead to symptoms of belching than flatulence.


Much of the food that you eat is carbohydrates, which are made up of long chains of sugar molecules.

Some carbohydrates cannot be digested and absorbed in the intestines, and pass down into your colon.

These types of carbohydrates are known as unabsorbable carbohydrates. 

Your colon is home to over 500 different types of bacteria. The bacteria begin to break down the carbohydrates and, in the process, produce gas which is released as flatulence.

Foods that contain a high amount of unabsorbable carbohydrates include:

  • beans,
  • broccoli,
  • cabbage,
  • cauliflower,
  • artichokes,
  • raisins,
  • pulses,
  • lentils,
  • prunes,
  • apples, and
  • Brussel sprouts.

Slimming products that contain the sugar substitute, sorbitol, or fructose (a type of sugar) can also cause flatulence because both sorbitol and fructose are unabsorbable carbohydrates. Many fruit juices also contain high levels of fructose.

As many of the foods that contain unabsorbable carbohydrates are digested over a longer period of time, any undigested food can eventually begin to decompose. This releases a small amount of sulphar gas which causes the foul smell that is associated with flatulence.

Health conditions

Health conditions that can cause symptoms of flatulence include:

  • constipation,
  • irritable bowel syndrome (IBS),
  • coeliac disease - a condition that is caused by a food intolerance to a protein called gluten and is found in wheat, rye, and barley, and
  • lactose intolerance - lactose is a natural sugar that is found in milk.


Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
The thyroid is a jointed piece or cartilage that enclosed the vocal cords and forms the ‘Adam’s apple’ in men.
Enzymes are proteins that speed-up and control chemical reactions, such as digestion, in the body.
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
The sac-like organ of the digestive system. It helps digest food by churning it and mixing it with acids to break it down into smaller pieces.
The anus is the opening at the end of the digestive system where solid waste leaves the body.
Constipation is when you pass stools less often than usual, or when you are having difficulty going to the toilet because your stools are hard and small.
Last updated: 04 October 2011

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