Here's why:
* Saliva contains salivary amylase: This enzyme begins breaking down starch into smaller sugars like maltose. This process starts in the mouth even before the food reaches the stomach.
* Other macromolecules are not immediately targeted: While the digestive system works on breaking down all macromolecules (proteins, lipids, carbohydrates), starch is the only one that is initially targeted by an enzyme in the mouth.
Note: While starch is the first to be enzymatically attacked, the breakdown process of other macromolecules like proteins (by pepsin in the stomach) and fats (by lipases in the small intestine) begins later in the digestive tract.
