5 ms·

The mirror molecule of glucose tastes the same but has no caloric value because our bodies chemistry is depended on the handedness of a molecule. It is however

by wrnr 6y ago

The mirror molecule of glucose tastes the same but has no caloric value because our bodies chemistry is depended on the handedness of a molecule. It is however very expensive to make because all of nature prefers the same handedness. No natural sources exist, because is is useless from an evolutionary point of view. It is however possible that extra-terrestrial-life uses the opposite handedness, so they send a bunch of very expensive sugar to mars to test if there is life there.

acchow 6y ago
However, turns out L-glucose is a laxative. If our enzymes can't bind to it, what is causing this physiological response?
- roywiggins 6y ago
  Reddit agrees with my first instinct that it probably draws water into your gut via osmosis. https://www.reddit.com/r/todayilearned/comments/2347u0/til_that_glucose_sugar_has_an_opposite_handed/cgtecw5/ https://www.reddit.com/r/todayilearned/comments/2347u0/til_t...
  - refurb 6y ago
    The other reason is that often the bacteria in your gut can metabolize sugars that our own enzymes can't. They basically go nuts with a huge food source. You get gas and diarrhea because of their waste products.
    - novia 6y ago
      You're being downvoted because EVERY form of life on earth discovered so far metabolizes D-Glucose. If you find a microbe with the ability to metabolize L-Glucose it'll be big news, and most likely an alien.
      - dwohnitmok 6y ago
        Not quite. "An L-glucose catabolic pathway in Paracoccus species 43P" https://pubmed.ncbi.nlm.nih.gov/23038265/ https://pubmed.ncbi.nlm.nih.gov/23038265/ But it's true the vast vast majority of life on earth cannot metabolize L-glucose and it would be unlikely to have bacteria in your gut capable of metabolizing it.
- ars 6y ago
  The sugar is not digested so it remains in the gut. Then the sugar, because of osmosis, draws water in from the surrounding tissue. This extra water then causes the laxative effect.
  - m463 6y ago
    and then you lose weight (water weight)
- meiraleal 6y ago
  It is weird to imagine that the evolution is to eat a laxative cake in place of taking care of sugar addiction. "Hey! This version of cocaine makes you still feel hungry!"
Animats 6y ago
It's straightforward to convert sugar to "invert sugar", with both isomers. So you can get down to 50% calories. Left-handed sugar still seems to be hard to isolate, though. Merck sells it for about US$108/gram.[1] Too much even for expensive restaurants. However, there's a new synthesis method available. Could have startup potential.[2] [1] https://www.sigmaaldrich.com/catalog/product/sigma/g5500?lang=en&region=US https://www.sigmaaldrich.com/catalog/product/sigma/g5500?lan... [2] https://www.researchgate.net/publication/237860195_L-Glucose_A_convenient_synthesis_from_D-glucose https://www.researchgate.net/publication/237860195_L-Glucose...
- ars 6y ago
  That's not what invert sugar is.
ashtonkem 6y ago
I wonder if this would still trigger an insulin spike. It's been hypothesized that an insulin spike after consuming artificial sweeteners is at least part of why those who switch to them often don't lose the weight they expected (this process is verified in vitro and in rats, but not in humans to my knowledge). If an insulin spike still happens, it will cause a "sugar crash", which will typically drive extra consumption even if the original source was calorie free.
doctoboggan 6y ago
Interesting video from Steve Mould covering this topic: https://www.youtube.com/watch?v=975r9a7FMqc https://www.youtube.com/watch?v=975r9a7FMqc
aidenn0 6y ago
Totally off topic, but why is it L and D instead of L and R or S and D?
- ac29 6y ago
  Its from Latin: https://en.wiktionary.org/wiki/laevus#Latin https://en.wiktionary.org/wiki/laevus#Latin https://en.wiktionary.org/wiki/dexter#Latin https://en.wiktionary.org/wiki/dexter#Latin
  - jfengel 6y ago
    Science seems to have gone with "levo-" prefixes rather than "sinistro-", though "sinistrorotary" does see occasional usage[1]. [1] https://www.google.com/search?q=sinistrorotatory&sxsrf=ALeKk02WVOTiWQZ1Tg-d4QGbHLoS6kJWeg:1601661140574&source=lnms&tbm=bks&sa=X&ved=2ahUKEwjRg9bavJbsAhXylHIEHS9sAKwQ_AUoAXoECAsQCQ&biw=873&bih=732 https://www.google.com/search?q=sinistrorotatory&sxsrf=ALeKk...

by wrnr 6y ago

acchow 6y ago

However, turns out L-glucose is a laxative. If our enzymes can't bind to it, what is causing this physiological response?

roywiggins 6y ago
Reddit agrees with my first instinct that it probably draws water into your gut via osmosis. https://www.reddit.com/r/todayilearned/comments/2347u0/til_that_glucose_sugar_has_an_opposite_handed/cgtecw5/ https://www.reddit.com/r/todayilearned/comments/2347u0/til_t...
- refurb 6y ago
  The other reason is that often the bacteria in your gut can metabolize sugars that our own enzymes can't. They basically go nuts with a huge food source. You get gas and diarrhea because of their waste products.
  - novia 6y ago
    You're being downvoted because EVERY form of life on earth discovered so far metabolizes D-Glucose. If you find a microbe with the ability to metabolize L-Glucose it'll be big news, and most likely an alien.
    - dwohnitmok 6y ago
      Not quite. "An L-glucose catabolic pathway in Paracoccus species 43P" https://pubmed.ncbi.nlm.nih.gov/23038265/ https://pubmed.ncbi.nlm.nih.gov/23038265/ But it's true the vast vast majority of life on earth cannot metabolize L-glucose and it would be unlikely to have bacteria in your gut capable of metabolizing it.
ars 6y ago
The sugar is not digested so it remains in the gut. Then the sugar, because of osmosis, draws water in from the surrounding tissue. This extra water then causes the laxative effect.
- m463 6y ago
  and then you lose weight (water weight)
meiraleal 6y ago
It is weird to imagine that the evolution is to eat a laxative cake in place of taking care of sugar addiction. "Hey! This version of cocaine makes you still feel hungry!"

Animats 6y ago

It's straightforward to convert sugar to "invert sugar", with both isomers. So you can get down to 50% calories. Left-handed sugar still seems to be hard to isolate, though. Merck sells it for about US$108/gram.[1] Too much even for expensive restaurants. However, there's a new synthesis method available. Could have startup potential.[2] [1] https://www.sigmaaldrich.com/catalog/product/sigma/g5500?lang=en&region=US https://www.sigmaaldrich.com/catalog/product/sigma/g5500?lan... [2] https://www.researchgate.net/publication/237860195_L-Glucose_A_convenient_synthesis_from_D-glucose https://www.researchgate.net/publication/237860195_L-Glucose...

ars 6y ago
That's not what invert sugar is.

ashtonkem 6y ago

I wonder if this would still trigger an insulin spike. It's been hypothesized that an insulin spike after consuming artificial sweeteners is at least part of why those who switch to them often don't lose the weight they expected (this process is verified in vitro and in rats, but not in humans to my knowledge). If an insulin spike still happens, it will cause a "sugar crash", which will typically drive extra consumption even if the original source was calorie free.

doctoboggan 6y ago

Interesting video from Steve Mould covering this topic: https://www.youtube.com/watch?v=975r9a7FMqc https://www.youtube.com/watch?v=975r9a7FMqc

aidenn0 6y ago

Totally off topic, but why is it L and D instead of L and R or S and D?

ac29 6y ago
Its from Latin: https://en.wiktionary.org/wiki/laevus#Latin https://en.wiktionary.org/wiki/laevus#Latin https://en.wiktionary.org/wiki/dexter#Latin https://en.wiktionary.org/wiki/dexter#Latin
- jfengel 6y ago
  Science seems to have gone with "levo-" prefixes rather than "sinistro-", though "sinistrorotary" does see occasional usage[1]. [1] https://www.google.com/search?q=sinistrorotatory&sxsrf=ALeKk02WVOTiWQZ1Tg-d4QGbHLoS6kJWeg:1601661140574&source=lnms&tbm=bks&sa=X&ved=2ahUKEwjRg9bavJbsAhXylHIEHS9sAKwQ_AUoAXoECAsQCQ&biw=873&bih=732 https://www.google.com/search?q=sinistrorotatory&sxsrf=ALeKk...