What causes gas?
Gas forms from two main sources:

1. Air swallowed when eating foods - About 50% of the gas formed from swallowed air passes through the digestive tract and eventually be released as gas from the rectum. This gas is a combination of oxygen, nitrogen, hydrogen, carbon dioxide and methane. People swallow air as they eat and breath. Eating too fast, sucking through a straw, chewing gum or sucking hard candy can cause too much air to enter the body. Some swallowed air forms gas that can be released by belching.
2. Bacteria in the large intestine needed to digest foods - Gas forms when bacteria in your colon cause undigested carbohydrates to ferment in your small intestine. High-fiber foods—such as vegetables, fruits, whole grains and beans—do an excellent job at sweeping out your digestive tract. They also help regulate your cholesterol and blood sugar levels. But these fiber-rich foods also help the body produce gas. This is also true of fiber supplements that contain contain psyllium. Soda, beer and other carbonated drinks can also contribute to gas formation.

Risk factors
People with diets rich in high-fiber foods are more likely to experience problems with gas. But excess gas build up could be related to other factors or health concerns, including:

Antibiotic Use — Antibiotics destroy the normal bacterial flora in the bowel. These bacteria are essential for proper digestion and prevention of gas buildup.

Artificial sweeteners — Some people have a low tolerance for artificial sweeteners such as sorbitol and mannitol found in some sugar-free foods, gums, and candies. Some people develop gas and diarrhea when they eat these sweeteners.

Constipation — Constipation occurs when digest foods are not regularly expelled from your colon. This can also make it difficult to pass gas, which may lead to bloating and discomfort.

Food intolerances — Some people experience gas and bloating after eating dairy products. This occurs when the body is unable to process the lactose sugar in dairy foods. Other people are sensitive to foods that contain gluten, a protein found in wheat and some other grains. Eating these foods can also produce gas and diarrhea.

Health conditions — Chronic conditions such as diverticulitis, ulcerative colitis, or Crohn's disease can also lead to production of excess gas in the body. More serious conditions also increase the likelihood of abdominal distention such as cirrhosis, bowel obstruction or heart disease. Furthermore, cancer of the bowel, of the pancreas or the ovary and uterus can cause constipation and stop movement of faeces and gas through the bowel.

Laxative use — Overuse of laxatives may cause gas to build up in the body.

Medications - When combined, certain drugs, medications, substances or toxins may react causing Flatulence as a symptom.

Many of us know the telltale signs of gas. But what other symptoms accompany odor? And when does flatulence or belching becoming so problematic that should you ask for medical help? Continue reading the next section on Symptoms of Gas Pain to learn more.