Flatulence, commonly referred to as 'farting', is caused by gas in the bowel. Ordinarily, the intestines produce between 500 and 2000ml of gas, which is regularly passed out of the anus. The gas, or 'flatus', consists of a number of gases including methane, nitrogen and carbon dioxide. The varying smell depends on the ratio of gases, which is influenced by the foods eaten.
Flatus is generated by swallowed air and by digestion, notably of high-fibre food and also from the gaseous by-products of intestinal bacteria. Some digestive system disorders, such as irritable bowel syndrome, can produce excess gas.
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