What Are the Causes of Stomach Gas?

A person eats and drinks every day. As a normal part of the digestive process, her body processes the food and food components, as well as swallowed air, and handles it by allowing it to leave via the stomach (belching) or the rectum (passing gas). Some foods cause her to produce more gas than others; she may not react to some foods in the same way that others do. Most people will pass gas an average of 14 times daily.

Aerophagia

• Everyone who chews gum, drinks or eats quickly or smokes swallows small amounts of air. When a denture wearer's dentures are loose, he swallows air. When a person who is eating or drinking swallows air, it goes into the stomach. When he belches, this air, which contains oxygen, carbon dioxide and nitrogen, leaves his mouth. The small amount of gas remaining in his stomach migrates into his small intestine, where it will be partially absorbed. The small amount of gas which remains goes into the large intestine, where it will pass through the rectum. The person's stomach has added digestive juices because the stomach acid has combined with the bicarbonate in his digestive juices. When this happens, the stomach will release carbon dioxide. Most of this portion of gas will be absorbed into his blood stream.

Undigested Food

• The person's body will not digest and absorb some carbohydrates found in some foods in the small intestine because of a lack of some digestive enzymes. This undigested food passes from her small intestine into her large intestine where "good" harmless bacteria will break the food down. During this process, hydrogen and carbon dioxide are produced. Approximately one-third of all people will also produce methane as well. According to the National Digestive Diseases Information Clearinghouse, the person who also produces methane may not necessarily produce more gas, nor will she have any unique symptoms.

Sugars

• The sugars which produce gas are fructose, sorbitol and lactose. Lactose is milk sugar which is found in milk, cheese, ice cream, salad dressings, cereal, processed foods and bread. Fructose is found in pears, wheat, onions and artichokes. It is also found in fruit juices and sodas. Sorbitol is found in prunes, apples, pears and peaches. It is an added sweetener in sugar-free gums and candies, as well as in diet foods. These sugars can cause gas in the intestines.

Beans

• Raffinose is a sugar found in beans. It is a complex sugar and small amounts can be found in cabbage, broccoli, aparagus, brussels sprouts, whole grains and other vegetables. The person who has eaten one of these foods may notice he is more "gassy" after eating a meal. This is normal and not a sign of a digestive problem.

Starches

• Pastas, potatoes, corn and wheat will cause the person who has eaten them recently to produce and possibly pass gas. This will happen in the large intestine. By contrast, rice, which is also a starch, does not cause her to produce gas.

Fiber

• Fiber (soluble) reaches the large intestine, where the digestive process causes it to produce gas. Soluble fiber is one which, when mixed with water, dissolves and becomes a soft gel. Foods containing soluble fiber include beans, oat bran, most fruits and peas. Insoluble fiber passes completely through the intestines and causes little, if any, gas. Some vegetables and wheat bran have insoluble fiber in them.