Causes

Gas in your stomach is primarily caused by swallowing air when you eat or drink. Most stomach gas is released when you burp.

Gas forms in your large intestine (colon) when bacteria ferment carbohydrates — fiber, some starches and some sugars — that aren't digested in your small intestine. Bacteria also consume some of that gas, but the remaining gas is released when you pass gas from your anus.

Common foods that cause gas

Certain high-fiber foods may cause gas, including:

• Beans and peas (legumes)
• Fruits
• Vegetables
• Whole grains

While high-fiber foods increase gas production, fiber is essential for keeping your digestive tract in good working order and regulating blood sugar and cholesterol levels.

Other dietary factors

Other dietary factors that can contribute to increased gas in the digestive system include the following:

• Carbonated beverages, such as soda and beer, increase stomach gas.
• Eating habits, such as eating too quickly, drinking through a straw, chewing gum, sucking on candies or talking while chewing results in swallowing more air.
• Fiber supplements containing psyllium, such as Metamucil, may increase colon gas.
• Sugar substitutes, or artificial sweeteners, such as sorbitol, mannitol and xylitol, found in some sugar-free foods and beverages may cause excess colon gas.

Medical conditions

Medical conditions that may increase intestinal gas, bloating or gas pain include the following:

• Chronic intestinal disease. Excess gas is often a symptom of chronic intestinal conditions, such as diverticulitis, ulcerative colitis or Crohn's disease.
• Small bowel bacterial overgrowth. An increase or change in the bacteria in the small intestine can cause excess gas, diarrhea and weight loss.
• Food intolerances. Gas or bloating may occur if your digestive system can't break down and absorb certain foods, such as the sugar in dairy products (lactose) or proteins such as gluten in wheat and other grains.
• Constipation. Constipation may make it difficult to pass gas.