flatus

Flatus, or flatulence, is the expulsion of intestinal gas from the anus. It is a normal bodily function resulting from swallowed air and the gaseous byproducts of digestion and microbial fermentation in the colon.

Most intestinal gas consists of nitrogen and hydrogen, with varying amounts of carbon dioxide, methane, and trace gases such as hydrogen sulfide. Gas is produced when dietary carbohydrates and other substances reach the large intestine and are fermented by gut bacteria; some gas is also swallowed air during eating or drinking. A portion of swallowed air is belched rather than passed rectally.

Gas production varies with diet and biology. Foods rich in fermentable carbohydrates, such as beans, certain vegetables, and dairy in lactose-intolerant individuals, can increase gas. Other contributors include carbonated drinks, artificial sweeteners, and rapid eating. Medical conditions such as lactose intolerance, fructose malabsorption, celiac disease, irritable bowel syndrome, small intestinal bacterial overgrowth, and certain infections can increase flatulence.

Management focuses on dietary modification and symptomatic relief. Keeping a food diary, limiting fermentable carbohydrates (low-FODMAP approach), gradual dietary changes, and avoiding gum chewing or rapid swallowing can help. Enzyme supplements (lactase for lactose intolerance) and over-the-counter products containing simethicone may reduce symptoms; sometimes probiotics are tried. Treatment of underlying conditions is important if gas is persistent or accompanied by other symptoms such as pain, weight loss, or blood in stool.

Flatus is a common, normally harmless process, with frequency that varies widely between individuals. If there are red flags or persistent distress, medical evaluation is advised.