MUDr. Dana Maňasková


Vyhledávání na medicinman.cz
 

leky-latky/sacharidy/nazvoslovi

Free sugars glucose, fructose, sucrose

  • Glucose and fructose joined by glycosidic bond
  • Mixtures of glucose: fructose
    • Honey (approximately 50:50)
  • High-fructose
    • Corn syrup (HFCS; 42% or 55% of fructose, named HFCS42 or HFS55, respectively)
  • Naturally contained
    • Intact fruits (glucose, fructose, sucrose, and others)
    • Milk (lactose: glucose plus galactose joined by a glycosidic bond)
  • Added sugars
    • All sugars used as ingredients in processed and prepared foods
  • Glucose in foods as unbound glucose
    • Grapes, honey and HFCS
  • Glucose part of disaccharides/oligosaccharides
    • Sucrose, lactose and raffinose
  • Attached to other dietary compounds - bound to the aglycone
    • Part of many dietary polyphenols
  • Monomer of polysaccharides of plant or animal origin
  • Fructose is mainly found in food as
    • Sucrose
    • Unbound fructose (as it occurs in fruits, honey and HFCS)
    • Monomer of undigestible fructo-oligosaccharides and fructans (e.g., inulin)
  • Table sugar (sucrose)
    • Most representative ingredient used as sweetener
  • 1970s and onwards
    • Inexpensive industrial conversion of glucose from cornstarch to fructose
  • Intake of free sugars in children
    • May contribute to 18.5% of total calories
    • Being SSB the major single contributor in this category
Glucose is physiologically crucial since it is the center of a homeostatic neuroendocrine system that controls the blood levels of this monosaccharide across the feed-fasting cycle, which is disrupted in hyperglycemia of diabetes. On the other hand, fructose is only a crucial cellular nutrient as the primary energy source of sperm [54]. Although glucose and fructose are similar molecules, they differ in their transport and metabolism, both in the small intestine and in the liver. In the liver, a description of glucose metabolism in comparison to that of fructose is extensively described by Lustig et al. [55]. After ingestion of fructose, this monosaccharide is rapidly absorbed in enterocytes via GLUT5 (apical membrane) and GLUT5/GLUT2 (basolateral membrane), entering in the liver through GLUT2/GLUT8 transporters [54] (Figure 1). Fasting plasma levels of fructose are very low (10–50-fold lower than glucose), and even a large ingestion of this monosaccharide leads to small increases in its circulating levels (reaching 3–11 mg/dL), given that most fructose (>85%) is cleared in the splanchnic extraction [56]. It is assumed that fructose is mainly metabolized in the liver [54], although a recent report using isotope tracers in mice challenges this idea, also indicating a critical role of small intestine in fructose metabolism [57]. However, the shorter relative size of small intestine in humans versus mice still suggests a greater importance of liver versus intestine in fructose metabolism in humans [58].

Synonyma

  • Sacharidy (od glukozy až po vlákninu)
  • Glycidy (řecky gluco = sladký)
  • cukry (legislativa na etiketách nyní slovo cukry nevnímá jako synonymum sacharidů jak je to v biochemii, ale jako výraz pro jednoduché cukry)
  • Karbohydráty (člvěk by si řekl: "uhlovodíky, tedy včetně ropy", jenže anglická literatura si z toho udělala sacharidy)
  • Uhlovodany (laicky zkomolený překlad anglického carbohydrates)
O úroveň výše

Poslední aktualizace: 13. 7. 2019 0:48:05