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Sugar isn't just a glucose disacharide, its got fructose, which is functionally not a carb. It can only be metabolized in the liver, and in large enough quantit

by ravar 6y ago

Sugar isn't just a glucose disacharide, its got fructose, which is functionally not a carb. It can only be metabolized in the liver, and in large enough quantities your liver is forced to metabolize fructose into fat, which taken far enough leads non alcoholic fatty liver disease. Glucose won't do that to you.

killjoywashere 6y ago
Fructose is definitely a carb. It's not a direct reactant in Kreb's cycle, but there are plenty of ways to move fructose through the metabolic pathways so the oxidation of those carbons results in the production of ATP. Also, I wouldn't use "It can only be metabolized by the liver" as evidence of fructose's carbohydrate status: a) that has nothing to do with the definitions, and the statement is true for a very large number of molecules.
- ravar 6y ago
  Emphasis on my wording, functionally not a carb. Its not treated how carbs normally are.
  - just-juan-post 6y ago
    Could you elaborate? I'm reading this on wikipedia: > Under one percent of ingested fructose is directly converted to plasma triglyceride.[2] 29% - 54% of fructose is converted in liver to glucose, and about a quarter of fructose is converted to lactate. 15% - 18% is converted to glycogen.[3] Glucose and lactate are then used normally as energy to fuel cells all over the body. https://en.wikipedia.org/wiki/Fructolysis https://en.wikipedia.org/wiki/Fructolysis
    - ravar 6y ago
      I can't find my source[1], but the amount of fructose converted to glucose is highly dose dependent. Over 30 grams (if i remember correctly) it basically all gets shunted to fat. edit: [1]https://onlinelibrary.wiley.com/doi/pdf/10.1111/joim.12993 https://onlinelibrary.wiley.com/doi/pdf/10.1111/joim.12993
samatman 6y ago
Yes, I'll grant you that fructose and glucose aren't bio-identical foods. A human can only absorb about 30 grams of fructose in an hour, and it looks like if we get well north of 120 grams in a day, bad things can happen. That's sixty grams of sugar, or about 55 of high fructose corn syrup. Can't be more than 200 grams of flour in a twelve-inch subway, so twenty grams of sugar? You'll be fine. Just, maybe don't get that fountain drink to go with it...
- 01100011 6y ago
  > human can only absorb about 30 grams of fructose in an hour Absorb or metabolize? I'd be interested in seeing any references for what you're talking about. I've heard before that fructose can lead to problems in excess, so it would be great to know some quantative guidelines for safe consumption.
  - samatman 6y ago
    I can't speak to the site in general, but this article is broadly in keeping with my own understanding: https://www.climbingnutrition.com/diet/fructose/ https://www.climbingnutrition.com/diet/fructose/ There are some references as links, would be nice to find something drier with a thicket of refs at the bottom. As usual, Le Wik delivers, though I'd enjoy seeing this section expanded: https://en.wikipedia.org/wiki/Fructose#Fructose_digestion_and_absorption_in_humans https://en.wikipedia.org/wiki/Fructose#Fructose_digestion_an...
powersnail 6y ago
Very baffled second language speaker here. Terminologies regarding nutrients confuse me to no end. Isn't carb an abbreviation of carbohydrate, which in turn is a synonym of saccharide? How come fructose is a monosaccharide but not functionally a "carb"?
- akdor1154 6y ago
  Not OP, but I think by "(not) functionally a carb" OP means "(not) processed as carb by your body". Functionally => how it functions, how it interacts with something else, c.f. "functional testing" :) Unsure if this is nutritional terminology or just HN-reader terminology.
  - powersnail 6y ago
    That make sense, thanks!
- andy_ppp 6y ago
  Because your body processes fructose through a different potentially more damaging pathway than glucose. It’s a carb if you like but it’s the worst carb for you by a huge margin, especially when eaten without fibre.
deleted 6y ago
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by ravar 6y ago

killjoywashere 6y ago

Fructose is definitely a carb. It's not a direct reactant in Kreb's cycle, but there are plenty of ways to move fructose through the metabolic pathways so the oxidation of those carbons results in the production of ATP. Also, I wouldn't use "It can only be metabolized by the liver" as evidence of fructose's carbohydrate status: a) that has nothing to do with the definitions, and the statement is true for a very large number of molecules.

ravar 6y ago
Emphasis on my wording, functionally not a carb. Its not treated how carbs normally are.
- just-juan-post 6y ago
  Could you elaborate? I'm reading this on wikipedia: > Under one percent of ingested fructose is directly converted to plasma triglyceride.[2] 29% - 54% of fructose is converted in liver to glucose, and about a quarter of fructose is converted to lactate. 15% - 18% is converted to glycogen.[3] Glucose and lactate are then used normally as energy to fuel cells all over the body. https://en.wikipedia.org/wiki/Fructolysis https://en.wikipedia.org/wiki/Fructolysis
  - ravar 6y ago
    I can't find my source[1], but the amount of fructose converted to glucose is highly dose dependent. Over 30 grams (if i remember correctly) it basically all gets shunted to fat. edit: [1]https://onlinelibrary.wiley.com/doi/pdf/10.1111/joim.12993 https://onlinelibrary.wiley.com/doi/pdf/10.1111/joim.12993

samatman 6y ago

Yes, I'll grant you that fructose and glucose aren't bio-identical foods. A human can only absorb about 30 grams of fructose in an hour, and it looks like if we get well north of 120 grams in a day, bad things can happen. That's sixty grams of sugar, or about 55 of high fructose corn syrup. Can't be more than 200 grams of flour in a twelve-inch subway, so twenty grams of sugar? You'll be fine. Just, maybe don't get that fountain drink to go with it...

01100011 6y ago
> human can only absorb about 30 grams of fructose in an hour Absorb or metabolize? I'd be interested in seeing any references for what you're talking about. I've heard before that fructose can lead to problems in excess, so it would be great to know some quantative guidelines for safe consumption.
- samatman 6y ago
  I can't speak to the site in general, but this article is broadly in keeping with my own understanding: https://www.climbingnutrition.com/diet/fructose/ https://www.climbingnutrition.com/diet/fructose/ There are some references as links, would be nice to find something drier with a thicket of refs at the bottom. As usual, Le Wik delivers, though I'd enjoy seeing this section expanded: https://en.wikipedia.org/wiki/Fructose#Fructose_digestion_and_absorption_in_humans https://en.wikipedia.org/wiki/Fructose#Fructose_digestion_an...

powersnail 6y ago

Very baffled second language speaker here. Terminologies regarding nutrients confuse me to no end. Isn't carb an abbreviation of carbohydrate, which in turn is a synonym of saccharide? How come fructose is a monosaccharide but not functionally a "carb"?

akdor1154 6y ago
Not OP, but I think by "(not) functionally a carb" OP means "(not) processed as carb by your body". Functionally => how it functions, how it interacts with something else, c.f. "functional testing" :) Unsure if this is nutritional terminology or just HN-reader terminology.
- powersnail 6y ago
  That make sense, thanks!
andy_ppp 6y ago
Because your body processes fructose through a different potentially more damaging pathway than glucose. It’s a carb if you like but it’s the worst carb for you by a huge margin, especially when eaten without fibre.

deleted 6y ago

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