Editing Flatulence (section)

===Excessive volume===
The range of volumes of flatus in normal individuals varies hugely (476–1,491&thinsp;mL/24&thinsp;h).<ref name="Tangerman 2009" /> All intestinal gas is either swallowed environmental air, present intrinsically in foods and beverages, or the result of gut fermentation.

Swallowing small amounts of air occurs while eating and drinking. This is emitted from the mouth by eructation (burping) and is normal. Excessive swallowing of environmental air is called [[aerophagia]], and has been shown in a few case reports to be responsible for increased flatus volume. This is, however, considered a rare cause of increased flatus volume. Gases contained in food and beverages are likewise emitted largely through eructation, e.g., carbonated beverages.

Endogenously produced intestinal gases make up 74 percent of flatus in normal subjects. The volume of gas produced is partially dependent upon the composition of the intestinal microbiota, which is normally very resistant to change, but is also very different in different individuals. Some patients are predisposed to increased endogenous gas production by virtue of their gut microbiota composition.<ref name="Azpiroz 2005" /> The greatest concentration of gut bacteria is in the colon, while the small intestine is normally nearly sterile. Fermentation occurs when unabsorbed food residues arrive in the colon.

Therefore, even more than the composition of the microbiota, diet is the primary factor that dictates the volume of flatus produced.<ref name="Azpiroz 2005" /> Diets that aim to reduce the amount of undigested fermentable food residues arriving in the colon have been shown to significantly reduce the volume of flatus produced. Again, increased volume of intestinal gas will not cause bloating and pain in normal subjects. Abnormal intestinal gas dynamics will create pain, distension, and bloating, regardless of whether there is high or low total flatus volume.