Causes and triggers

Lactose intolerance occurs when the enzyme lactase is either not present in the body, or only present in insufficient quantities. This means that lactose is not broken down in the small intestine, but lands instead in the large intestine, where it is broken down by bacteria into five components: lactic acid, carbon dioxide, methane, hydrogen, and acetic acid. This gas production leads to the bloating typical of lactose intolerance. The water content in the large intestine also rises, because lactose binds with water. Together with the acid production, this affects the digestive process, leading to bloating.

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