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. 2021 Aug 2;80(2):255–270. doi: 10.1093/nutrit/nuab012

Table 3.

Chemical and physiological characteristics of rare sugars

Rare sugar Structure Caloric content (kcal/g) Sweetness (compared with sucrose) Glycemic index Gut enzymes and metabolic fate
Allulose

Monosaccharide

 

(C-3 epimer of fructose)

0.240 70%41 ND Transported via GLUT5 in the enterocyte and further transported using GLUT2 (same as fructose)49
L-arabinose

Monosaccharide

 

(aldopentose)

050 ∼50%51 ND Inhibited sucrase activity2
D-tagatose

Monosaccharide

 

(C-4 epimer of fructose)

(∼1.5–3)43 92%42 352 Transported via GLUT5 in the enterocyte, metabolized via glycolytic pathway (same as fructose),2 fermented in the colon53
Trehalose Dissacharide (2 glucose molecules in an α1,1-glycosidic linkage) 444 ∼50%45 ND Trehalose broken down by trehalase in the small intestine into 2 glucose molecules, which are then absorbed54
Isomaltulose (palatinose) Disaccharide (glucose and fructose in an α1-6 glycosidic bond) 446 50%47 3252 Completely but slowly digested by isomaltase37
Kojibiose Disaccharide (2 glucose molecules connected by an α1-2 glycosidic bond) ND ND ND ND
Sorbose

Monosaccharide

 

(Ketose)

ND 70%48 ND ND
D-allose

Monosaccharide

 

(C-3 epimer of glucose)

ND 80%48 ND Downregulated GLUT1 expression55