Salivary amylase can indeed decompose starch, but the amount of saliva secretion is limited, and the amount of salivary amylase in saliva is even more limited, so the amount of starch that can be decomposed and consumed is naturally limited. When eating, the main function of saliva is to lubricate food for swallowing, while amylase in saliva decomposes part of starch mainly to increase the taste of food, and food has a certain digestive effect after entering the stomach.