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2004/04/29, 12:06 PM
Usually it's your diet.. here's what I found:
Two Main Gas Sources:
1) Swallowed air. Aerophagia is the swallowing of air and is usually followed by eructations (burping). For some people the amount of gas swallowed can cause flatulence. Swallowed air can be determined to be the source of the excess bowel gas by finding a large amount of nitrogen in the flatus sample. About 80% of air is nitrogen. Determining that the excess bowel gas is due to swallowed air, rather than a problem with the bowel itself, can save an expensive and uncomfortable series of tests for the patient.
2) Bowel Produced Gas. The major source of gas in the bowel for almost everyone is the normal metabolic activity of colonic bacteria on our partially digested foodstuffs. Carbohydrates that have not been absorbed by the processes of normal digestion with enzymes in the small intestine are commonly known as dietary fiber. These undigested fibers move into the large intestine (colon) where bacteria break them down by the process known as fermentation into a gaseous mixture consisting primarily of: nitrogen (N2), oxygen (O2), carbon dioxide (CO2), hydrogen (H2) and methane (CH4). These gases are all odorless and colorless. There are also small amounts of odoriferous sulfur-containing substances produced, like hydrogen sulfide, methanethiol, and dimethyl sulfide.
The most common source of undigested carbohydrate in the American diet is lactose from dairy products, such as milk, skim milk, and yogurt (cheeses contain little lactose). The second leading gas-producing foods are legumes (beans, peas, and lentils). Whether they are served as “beans with hot dogs,” or in a “low-fat vegetarian chili,” legumes all cause gas because they contain two relatively indigestible sugars, raffinose and stachyose, that end up in the large intestine.
All unrefined plant foods, including grains, fruits, and vegetables, contain undigestible fibers that end up being fermented in the large intestine by bowel bacteria into odorless gas. Refining grains into white flour and rice removes most of the indigestible carbohydrates (dietary fiber). White rice has been shown to be one complex carbohydrate that is nearly completely absorbed by the small intestine resulting in almost no indigestible carbohydrate for bacteria to turn into flatus.4
See the whole article here: http://www.travelwizard.com/healthwellness/mcdougall-articles-aug02-meat.html
another decent one here: http://my.webmd.com/content/article/79/96312.htm
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