Flatulence is gas or air that collects in the stomach or intestines, causing discomfort — and its eventual release. The gas comes from two sources: swallowed air, and the bacterial fermentation of undigested carbohydrates — fibre, resistant starch, and the oligosaccharides of beans — in the colon. A healthy gut produces it constantly; diet sets the volume. The discomfort of trapped wind — bloating, cramps, distension — is one of the commonest digestive complaints, and the social awkwardness of its release is one of humanity’s oldest jokes. Dietitians distinguish normal flatulence, a sign of a fibre-fed microbiome, from the excessive wind of malabsorption, IBS, or enzyme deficiency. It is the audible byproduct of digestion — the gut’s fermentation made public.