What is the principal carbohydrate found in milk?

The principal carbohydrate found in milk is lactose. Lactose is a disaccharide composed of two simpler sugars: glucose and galactose. It is unique to milk and dairy products, serving as a crucial source of energy for newborn mammals. Upon digestion, lactose is broken down by the enzyme lactase into glucose and galactose, which can then be absorbed into the bloodstream for use by the body's cells.

In addition to its role as an energy source, lactose contributes to the sweetness of milk and can influence the texture and flavor profile of various dairy products. The presence of lactose is also what distinguishes dairy from non-dairy products in terms of carbohydrate content.

The other options mentioned—glucose, fructose, and galactose—are present in various foods but are not the main carbohydrate found in milk. Glucose is a simple sugar that serves as a primary energy source for many organisms, while fructose is commonly found in fruits and honey. Galactose, although a component of lactose, does not occur in significant amounts on its own in milk. Therefore, understanding that lactose is the predominant carbohydrate in milk is essential for grasping the nutritional profile of dairy products.