What condition is characterized by the inability to digest the disaccharide lactose?

Lactose intolerance is the condition characterized by the inability to digest lactose, which is a disaccharide sugar found primarily in milk and dairy products. This occurs due to a deficiency in lactase, the enzyme responsible for breaking down lactose into its components, glucose and galactose, for absorption in the intestine. When lactose is not properly digested, it can lead to gastrointestinal symptoms such as bloating, diarrhea, and abdominal pain after consuming lactose-containing foods.

Understanding this condition is essential because it directly affects dietary choices and can lead to nutrient deficiencies if dairy products are eliminated without appropriate substitutions. Other conditions listed, such as gluten sensitivity and coeliac disease, pertain to adverse reactions to gluten, while fructose malabsorption involves difficulty digesting fructose, not lactose.