Malabsorption of Carbohydrates

摘要

Carbohydrates are responsible for 25-50% of daily energy intake. The carbohydrate composition of the diet changes with age. In breast milk and standard infant formulas, lactose is the only or predominant carbohydrate; starches and other sugars follow with the introduction of 'beikost'. In the healthy, balanced diet of children and adults starches (and fiber) should prevail. The small bowel only absorbs monosaccharides, so dietary carbohydrates have to be hydrolyzed into their constituent monosaccharides glucose, galactose and fructose. Glucose and galactose are actively transported, while fructose absorption takes place through facilitated diffusion. Not all dietary carbohydrates can be hydrolyzed by human digestive enzymes. Unabsorbed carbohydrate enters the colon as a fuel for the gut microflora. While this is a physiologic process essential for normal colonic function, especially short-chain soluble carbohydrates may surpass the fermentative capacity of the colonic flora.