Category: sugar
Aliases: D-Galactose, Brain sugar, Cerebrose
Aldohexose monosaccharide (C₆H₁₂O₆), a C-4 epimer of glucose and the constituent of lactose, raffinose and myelin galactolipids. Absorbed across the enterocyte apical membrane by Na⁺-coupled SGLT1 (shared with glucose) and exported basolaterally via GLUT2. Hepatic clearance proceeds through the Leloir pathway: galactokinase (GALK1) phosphorylates it to galactose-1-phosphate, which galactose-1-phosphate uridylyltransferase (GALT) converts with UDP-glucose to UDP-galactose (interconverted by UDP-galactose-4-epimerase, GALE) and glucose-1-phosphate, feeding glycogenesis and glycolysis. It is essentially non-insulinotropic acutely versus insulin-driving glucose. Loss-of-function GALT defines classic galactosemia; accumulated galactitol via aldose reductase drives cataract.
PO: 0.5h
No dedicated additive E-number (an endogenous nutritive sugar, not an authorized tabletop sweetener); roughly 0.3–0.65× as sweet as sucrose. No numeric ADI — treated as a normal dietary carbohydrate; key flag is classic galactosemia (GALT deficiency), where dietary galactose/lactose is toxic and must be avoided.