Table 2.

Chemical and physiological characteristics of sugars and other glycemic carbohydrates.

CHO	Type	Digestive enzyme	In gut lumen	Enterocyte uptake	In blood	Possible metabolic fate options	GI
Glucose	Monosaccharide	-	Glucose	-	Glucose	Used as fuel, stored as glycogen and/or converted to other metabolites	100
Fructose	Monosaccharide	-	Fructose	-	Lactate, glucose, fructose	Partially converted to lactic acid and glucose, used as fuel or stored as glycogen, and fatty acids used as fuel or triacylglycerol stored as lipid	19
Sucrose	Disaccharide: glucose -fructose, α1-2 bond	Sucrase	Glucose, fructose	Glucose, fructose	glucose, lactate, fructose	see glucose and fructose above	65
Isomaltulose	Disaccharide: glucose -fructose, α1-6 bond	Isomaltase	Glucose, fructose	Glucose, fructose		See fate of glucose and fructose above	32
Galactose	Monosaccharide	-	Galactose	-	Galactose	Liver conversion to glucose, see fate of glucose above	25
Lactose	Disaccharide: glucose -galactose, α1-4 bond	Lactase	Glucose, galactose	Glucose, galactose	Glucose, galactose	See fate of glucose and galactose above	45
Honey	Glucose 30.3%, fructose 38.4%, sucrose 1.3%	Sucrase	Glucose, fructose	Glucose, fructose	Glucose, lactate, fructose	See glucose and fructose above	50
Maple syrup	Sucrose 98%, glucose 1%, fructose 1%	Sucrase	Glucose, fructose	Glucose, fructose	Glucose, lactate, fructose	See glucose and fructose above	54
HFCS 55	Fructose 55%, glucose, 43% gluco-oligo saccharides 3%	α-Dextrinase	Glucose, fructose	Glucose, fructose	Glucose, lactate, fructose	See glucose and fructose above	58
Starch	Glucose polymers: amylopectin α1-4 and α1-6 bonds. Amylose α1-4 bonds	Amylase from saliva, pancreas	Maltose, glucose	Maltose, glucose	Glucose	See fate of glucose above	40–110*
Maltodextrins	Glucose polymer, α1-4 glycosidic bonds	α -Dextrinase	Glucose, maltose	Maltose, glucose	Glucose	See glucose above	110
Maltose	Disaccharide: glucose-glucose, α1-4 glycosidic bond	Maltase	Glucose	Glucose	Glucose	See glucose above	105
Trehalose	Disaccharide: glucose-glucose, α1-1 glycosidic bond	Trehalase	Glucose	Glucose	Glucose	See glucose above	70
Sorbitol*	Sugar alcohol	-	Sorbitol	-	Sorbitol	Liver conversion to fructose and glucose, see above	4

For a review of fructose, see Tappy and Lê (12). For a review of lactose and galactose, see University of Waterloo (13). One example of a low-caloric/low-glycemic sugar replacer is given. In the gut, sorbitol, a sugar-alcohol, is slowly absorbed (25–80% of the consumed dose) by facilitated diffusion. Absorbed sorbitol passes the liver, where it is converted to fructose and glucose (14). The unabsorbed fraction is transported to the large bowel, where it is fermented. When sorbitol is consumed in high doses, potential side effects can occur as a result of osmotic water shifts from blood into the gut, resulting in rumbling, loose stools, or diarrhea (extensive details about polyols can be found in Livesey (14), Ghosh and Sudha (15), Rice et al. (16). For a review of low- and non-caloric/non-glycemic sweeteners compared with caloric sweeteners, see Rogers et al. (17). *The glycemic index of starchy foods varies according to the molecular content of amylose, amylopectin, fiber, presence of protein, and characteristics of the food matrix, resulting in a range of reported values. For extensive glycemic index data [see (18)], International Tables of Glycemic Index and Glycemic Load Values, the online University of Sydney searchable data GI; http://www.glycemicindex.com/foodSearch.php. For further extensive details, see Queen Mary University London (19), Nomenclature of Carbohydrates (Available online at: https://www.qmul.ac.uk/sbcs/iupac/2carb/00n01.html#0121) and nomenclature of sugar alcohols (20).