Digestion and absorption of carbohydrates
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Carbohydrates are the major dietary sources of energy for humans. While most dietary carbohydrates are derived from multiple botanical sources, lactose and trehalose are the only animal-derived carbohydrates of relevance for human diet. The nutritional value of all carbohydrates depends on their digestion into monosaccharides by glucosidases of the gastrointestinal tract. Digestion of starch, the carbohydrate most abundantly consumed by humans, depends on the concerted activity of the six enzyme activities: salivary and pancreatic amylases, sucrase-isomaltase, and maltase-glucoamylase. Simpler carbohydrates such as sucrose, lactose, or trehalose only require the activities of sucrase, lactase, and trehalase, respectively, for their digestion. Glucose, galactose, and fructose are the main monosaccharides produced by digestion of dietary carbohydrates that are metabolized by humans. Depending on the requirements of individuals, these monosaccharides may follow metabolic pathways of either energy generation or energy storage. The imbalance between energy expenditure and dietary intake of energy-rich foods has a direct relationship to the development of diseases involving energy metabolism, such as obesity or diabetes. These effects have led to attempting the classification of carbohydrates based on their potential to induce physiologic effects in humans. However, to understand and manipulate the physiologic responses of the human organism to carbohydrate feeding, detailed studies to identify the multiple enzyme/substrate interactions among the large variety of available carbohydrates and the eight glucosidic activities of the human gastrointestinal tract are necessary. © 2009 by Taylor %26 Francis Group, LLC.