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Thread: 'Metabolised by the liver' page

  1. #1
    chronyx's Avatar
    chronyx is offline Senior Member
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    'Metabolised by the liver'

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    I had a random thought earlier.

    Please correct me if I am wrong, but fructose is metabolised solely by the liver, and this is given to be 'a bad thing'.

    MCT's, such as from coconut oil, have amongst the benefits listed in numerous websites online 'metabolised immediately by the liver', and this is given to be 'a good thing'


  2. #2
    js290's Avatar
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    Holy equivocation fallacy, Batman...

  3. #3
    chronyx's Avatar
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  4. #4
    Knifegill's Avatar
    Knifegill is offline Senior Member
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    MCT's bypass the digestive tract and go straight to the liver through a duct, and they are easy to digest with no nasty byproducts. It isn't just what the liver does, it's the molecular waste that ends up being of concern in most described scenarios. As for making the liver work hard, that IS stressful but largely avoidable by eating properly.

    Wait, where's your video? js290 always has a video!

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  5. #5
    IcarianVX's Avatar
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    It's not the fact that they are both metabolized by the liver that is the problem, it's how each is metabolized and the resulting byproducts (as Knifegill indicated) that is either the problem or the solution (good v. bad).

    LOL at the video thing. js290 is a smart dude, the videos just solidify what he says.
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  6. #6
    Apex Predator's Avatar
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    Fructose is handled as a toxin, coconut oil as a fuel.

  7. #7
    schreck's Avatar
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    Does anyone have any references to what exactly the difference between these two types of metabolism are?

    I'm curious about this too.

  8. #8
    tim_1522's Avatar
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    Quote Originally Posted by knifegill View Post
    wait, where's your video? Js290 always has a video!

  9. #9
    paleo-bunny's Avatar
    paleo-bunny is offline Senior Member
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    Fructose is metabolised by glycolysis in the liver, same pathway as glucose. Glucose enters this pathway before the rate-determining step, whereas fructose enters it after the rate-determining step. This means that fructose speeds up glycolysis much more than glucose does. There's lots of clever stuff evolved to prevent cells frying themselves by futile cycling (significant reactions in both directions on a pathway). The reverse of glycolysis is gluconeogenesis, whereby glucose is synthesised from pyruvate derived from amino acids (from protein) or glycerol.

    If a lot of fructose is absorbed by the liver this tends to speed up glycolysis with excess pyruvate having nowhere to go but be converted to fatty acids that are turned into triglycerides. These are the triglycerides associated with cardiovascular disease in people on SAD consuming too much sugar (sucrose and high fructose corn syrup).

    Someone on a low carb diet will have some gluconeogenesis going on - eating significant fructose in one sitting can obviously interfere with this.

    Another problem with fructose speeding up glycolysis is that can use up a lot of ATP, causing a shortage of energy for other metabolic and catabolic processes. A cell has to invest some ATP molecules in order to eventually get a lot more back when the end product of glycolysis is oxidised in the mitochondria. ATP is the universal energy currency of the body.

    Because fructose is so toxic in quantity it's absorbed from the gut much more slowly than glucose and other nutrients. This can contribute to candida overgrowth and gut dysbiosis.

    Fructose is much more carcinogenic and inflammatory that glucose as much higher percentage of it exists in the highly reactive open chain form than the ring form. Hence fructose damages important enzymes in the liver. The liver usually has to prioritise detoxing fructose over everything else.

    Modest quantities of fructose in fruit and vegetables are usually tolerated OK. Toleration levels vary. A lot of the low-carbers report that fruit sets off sugar cravings. I'm not surprised.
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