Stomach Gas and Flatulence

The gas that produces flatulence, however, happens a long way down the digestive tract from the stomach. Nonethess, what happens--or rather, what doesn't happen--in the stomach often starts the digestive process that results in flatulence.

There are certain foods that are not broken down efficiently by the stomach and small intestine. These are primarily sugars and polysaccharides. These substances pass through the stomach and small intestine undigested. They then proceed to the large intestine and the colon, where intestinal bacteria go to work on them. The interaction of these bacteria with the undigesteed food produces gases, much in the same way yeast produces carbon dioxide during the leavening of bread.

While this is happening, hydrogen and methane are being produced because the bacteria release minute vapors containing hydrogen sulfide (which largely accounts for the unpleasant odor of flatulence). Trace gases known as skatole and indole are also present.

Certain foods are known to produce an unusual amount of gas because they contain a lot of indigestible carbohydrates. As you might expect, certain kinds of beans are well known for this.

Swallowed air is not usually processed by the digestive system into the kinds of gas that occur in flatulence.

We don't know who did the study, but medical sources we found reported that the average adult passes gas about a dozen times a day.

We have related articles on stomach gas and stomach gas causes.