Foods That Cause Flatulence

Onions, tomatoes and mints actually relax the muscle at the lower end of the gullet, allowing air from the stomach to escape by belching.

Farting is more to do with bacteria in the lower bowel that are particularly partial to carbohydrates. The carbohydrates in some foods cannot be broken down and absorbed in the intestine; they pass straight through to the bowel, where they are fermented by the bacteria to produce gas that comes out as farting. Beans are famous for containing large amounts of unabsorbable carbohydrate, but other foods can have the same effect.

Some slimming chocolate contains sorbitol or fructose instead of sugar. Most of this is not absorbed (which is why these products are marketed for slimmers) but can be acted on by the large bowel bacteria to cause wind. Consumption of fruit juices is increasing and, because they contain a lot of fructose, they can cause gas and bloating.

Foods with a high proportion of unabsorbable carbohydrate that cause flatulence

  • Beans
  • Peas
  • Broccoli, cauliflower
  • Jerusalem artichokes and other root vegetables such as parsnips
  • Slimming foods that contain sorbitol or fructose
  • Raisins, prunes
  • Apples
  • Fruit juices (because of the fructose they contain)

Overeating, as we all know, leads to belching. This is because the stomach normally contains some air. When we overeat, the stomach attempts to relieve the discomfort and distension by expelling the stomach air upwards. This is a reflex over which we have no control.

Fizzy drinks and gulping hot drinks introduce gas into the stomach.

Habit. Some people suck a small amount of air into the oesophagus (gullet) or stomach by swallowing to make themselves belch, without realizing they are doing so (Gut 2004;53:1561). This habit often starts if there is a period of indigestion, when belching may temporarily relieve the discomfort.

Smoking, chewing gum and sucking on pen tops makes you produce more saliva, which has to be swallowed. Each time you swallow the saliva you also swallow air. Also, chewing gum contains sorbitol.

Tight clothing, such as Lycra shorts, constricting belts and hold-in underwear increase the pressure on the abdomen and may make it more difficult for wind to pass along normally, resulting in trapped wind and belching.

Acarbose is a drug sometimes used for diabetes. It prevents enzymes in the gut digesting carbohydrates such as starch and sucrose. Because they are not digested, these carbohydrates are not absorbed (which is how the drug helps to lower the blood sugar). Instead, they pass down to the lower bowel, where they are fermented by the bacteria. Most people taking acarbose experience flatulence, tummy rumbles and a feeling of fullness.

Intestinal diseases are occasionally responsible. In lactase deficiency, for example, the enzyme that breaks down lactose, a carbohydrate found in milk, is lacking. The undigested lactose produces hydrogen and carbon dioxide when it reaches the large bowel, causing frothy diarrhoea, griping pains and flatulence.

Constipation can cause farting. Normally, most of the intestinal gas is expelled out of the anus as small puffs which we are not aware of. When we are constipated, the gas becomes trapped behind the poo and then suddenly emerges as a noticeable amount. Also, when we are constipated, the food residues stay in the bowel for longer, and have more time to ferment and give off gases. (For more information, look at the section on constipation.)

Anxiety and tension seem to make wind worse. This is partly because when we are anxious, we are hyper-alert, and notice body functions that we would otherwise ignore. Another factor is that when we are anxious, we tend to swallow more air. Also, our guts become more active because of increased adrenaline levels and they expel the gases more forcefully.

Childbirth. After childbirth, the muscles of the anus or the nerves nearby can be damaged, making it difficult to hold wind in. This is much more common than many people realize. A study in Canada found that 25% of women were unable to control wind 5 months after giving birth, particularly if they had a long labour. The problem did improve a few months later. Sometimes, there may also be some leakage of poo (for more information, look at the section on faecal incontinence). If your problem started after having a baby and does not get better, see your doctor because an operation may cure the problem.

Ageing may make gas worse, because as we get older, we do not produce digestive juices, such as saliva, as efficiently. This means that more carbohydrate foods pass untouched to the lower bowel, where they are fermented by the bacteria.


First published on:
Reviewed and edited by: Dr Kevin Barrett
Last updated: October 2020

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