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Where does carbohydrate digestion begin in humans?

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A biochemical flowchart shows the metabolic pathways for carbohydrate utilization, including glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle. The diagram traces the conversion of glucose, fructose, and glycerol through various intermediates, leading to energy production, carbon dioxide release, and biosynthesis of amino acids and porphyrins. Key steps and branches are labeled, with colored boxes highlighting biosynthetic outputs. — Carbohydrate Pathways for the utilization of carbohydrates.

In humans, the digestion of carbohydrates begins in the mouth.1

When food is ingested, it is chewed and mixed with saliva, which contains the enzyme amylase. This enzyme initiates the breakdown of starches into smaller molecules. While only a small amount of starch is digested by salivary amylase, this process marks the start of carbohydrate chemical digestion before the food passes through the pharynx and esophagus into the stomach and eventually the duodenum, where the majority of digestion occurs.12