Ashish Das explains: Gas is formed in the intestines by the bacterial fermentation of intestinal contents. It is also called flatulence, and is passed out of the body via the rectum. Gastrointestinal gas has two sources. It is either swallowed air or produced by bacteria inhabiting the intestines, primarily in the colon.

Bacterial action on undigested foods like sugars and polysaccharides lead to the evolution of gases like hydrogen, methane etc. in the digestive tract. Sugars like lactose, sorbitol and fructose are commonly poorly digested and malabsorbed (when the body cannot digest a nutrient properly). Milk sugar or lactose is not digested due to the absence of the enzyme lactase in the lining of the intestines, which is a genetic trait. Thus consumption of milk leads to gas formation at times.

Reaction between the acidic fluid (in our stomach) and alkaline pancreatic juices results in the formation of both inorganic and nitrogenous gases. The body gets rid of these gases either by belching or passing wind. The usual cause of belching is excessive gas in the stomach that comes from swallowed air. However, discomfort in the abdomen for any reason may also cause belching. The treatment of excessive intestinal gas depends on the underlying cause that may include dietary changes and medications that reduce the amount of gas. Intake of antibiotics can also induce gas formation.

The question was sent by Biswajit Chakraborty from Burdwan.