DISORDERS AND FOODS ASSOCIATED WITH INCREASED GAS - As discussed above, the vast majority of people with gas-related complaints do not produce excessive amounts of gas. However, there are several conditions that may indeed lead to increased gas formation. The following sections will discuss some of the more common causes.

Aerophagia - Chronic, repeated belching usually results from habitual swallowing of large amounts of air (ie, aerophagia). Aerophagia is typically an unconscious process occurring with anxiety. The diagnosis is made after excluding other possible causes (such as gastroesophageal reflux disease). Treatment focuses on methods to help people refrain from swallowing excessive amounts of air, such as advising people to eat slowly without gulping, and avoid carbonated beverages, chewing gum, and smoking. Specific anti-anxiety treatment may also be necessary.

Foods that cause gas - As discussed above, several foods contain the carbohydrate raffinose, which is poorly digested and leads to gas production by the action of colonic bacteria. Common foods containing raffinose include beans, cabbage, cauliflower, Brussels sprouts, broccoli, and asparagus.

Starch and soluble fiber are other forms of carbohydrates that can contribute to gas formation. Potatoes, corn, noodles, and wheat produce gas while rice does not. Soluble fiber (found in oat bran, peas and other legumes, beans, and most fruit) also cause gas. Some laxatives contain soluble fiber and may cause gas, particularly during the first few weeks of use.

Lactose intolerance - Intolerance to lactose-containing foods (primarily dairy products) is a common problem. In Europe and the United States, lactose intolerance affects 7 to 20 percent in Caucasians (being lowest in those of northern European extraction), 80 to 95 percent among Native Americans, 65 to 75 percent of Africans and African Americans, and 50 percent of Hispanics. More than 90 percent of the population is affected in some regions in eastern Asia.

Lactose intolerance is caused by an impaired ability to digest lactose, the principle sugar in dairy products. Clinical symptoms of lactose intolerance include diarrhea, abdominal pain, and flatulence after ingestion of milk or milk-containing products.

Lactose intolerance can be diagnosed by a lactose breath test, in which a measured amount of lactose in consumed, and the amount of hydrogen in breath samples is measured. Treatment involves avoidance of dairy products that contain lactose and/or supplementation with the enzyme lactase, which is available in over-the-counter products. People who avoid dairy products should take calcium supplements, since dairy products are a valuable source of calcium.

Intolerance to other sugars - In addition to lactose and raffinose, some individuals may be intolerant to other sugars contained in foods. Two common examples are fructose (contained in onions, artichokes, and pears and in some fruit drinks or soft drinks where it appears as "high fructose corn syrup") and sorbitol (a sugar substitute contained in some sugar free candies and chewing gum).

Diseases associated with increased gas - A number of diseases can cause impaired absorption of carbohydrates (carbohydrate malabsorption), which can lead to increased gas. In addition to bacterial overgrowth described above, carbohydrate malabsorption can occur in patients with celiac disease (a disease caused by intolerance to a protein contained in wheat), short bowel syndrome, and those who have rare primary disorders of the enzymes needed to digest specific forms of carbohydrates.

Infections - Infections of the intestine are generally not a frequent cause of gas. However, infection with a parasite known as Giardia lamblia ("giardiasis") may cause abdominal discomfort, nausea, bulky stools, and carbohydrate malabsorption. Giardiasis occurs in people who ingest the cysts of the parasites, which are found in some rivers, streams, and wells.