Lactose intolerance is a common digestive problem. It occurs when the body cannot break down lactose. Lactose is the sugar found in milk and dairy products. The breakdown of lactose needs an enzyme called lactase. Lactase is produced in the small intestine. In people with lactose intolerance, lactase activity is low or absent.
When lactose is not digested, it stays in the gut. It draws water into the intestine. This can cause bloating and cramping. Bacteria in the colon ferment the undigested lactose. Fermentation produces gas and short‑chain fatty acids. The gas leads to flatulence. The fatty acids can irritate the colon lining.
Symptoms appear within 30 minutes to two hours after eating lactose. Common signs include diarrhea, nausea, and stomach pain. The severity of symptoms depends on how much lactose is consumed and how little lactase is present.
Diagnosis is usually done with a hydrogen breath test. Treatment involves limiting lactose intake. Lactase supplements can be taken before dairy meals. Many people find relief by choosing lactose‑free products.
Understanding the mechanism helps manage the condition. It also reduces unnecessary worry about dairy. With simple dietary changes, most people can enjoy meals without discomfort.