Lactase is an enzyme that is essential for the digestion of lactose, a disaccharide found mainly in milk and dairy products. This enzyme belongs to the hydrolases, a specific group of enzymes responsible for breaking down chemical bonds using water.

The role of lactase is to break down lactose into two simpler sugars – glucose and galactose, which are then absorbed into the blood and serve as a source of energy for cells.

Lactase is produced in the cells lining the small intestine, specifically in the microvilli, which are responsible for nutrient absorption. The activity of this enzyme is highest in infants, which makes sense since their main source of nutrition is milk.

However, over time, especially after weaning from breast milk, many people naturally experience a decrease in lactase activity, leading to a reduced ability to digest lactose. This phenomenon is known as lactase insensitivity, while in people who retain the ability to digest lactose into adulthood, the condition is referred to as lactase persistence. Genetically, persistence is the result of evolutionary adaptation to milk consumption in populations that domesticated cattle in the past, and milk became a significant component of their diet.

In addition to its biological importance, lactase also has wide application in industry. In the food industry, it is often used to produce low-lactose or lactose-free products intended for people with lactose intolerance.

These products are made by adding lactase directly to milk or dairy products, which breaks down the lactose into simple sugars before consumption. This process not only reduces the lactose content, but also increases the sweetness of the milk, as glucose and galactose are naturally sweeter than lactose alone.