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    Question Lactic acid calories?

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    Some months ago I started doing my own yogurt and kefir at home. I also successfully converted the milk kefir grains into water kefir ones, which I use for many things, just to name some: to trigger the fermentation of sauerkraut or to prepare a carbonated drink with little to no sugars but which tastes great and is a bomb of beneficial bacteria.

    But... I've always been wondering about the metabolism of lactic acid. To start with, does it bring calories? How many (if any, I assume they are less than the sugar it comes from)? Or has it negative calories as the body must get rid of it somehow? Does it interfere with insulin? With ketosis? Is lactic acid safe in quantities, or just something to assume from time to time?

    I have been looking for answers but with little success: many different contradicting opinions and no definitive, scientifically proven, response.

    Anybody?

    Thanks in advance!!!
    Last edited by primal_alex; 05-28-2012 at 01:59 PM.

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    Nobody's got information?

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    at least when your body produces lactic acid, it cycles back through the liver to make pyruvate. your body fuels this process with fat oxidation, and it burns calories.

    i have no idea how consuming lactic acid would work though... basically, i wouldn't count any potential calories in lactic acid, for any reason.

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    2 molecules of lactate require 6 ATP to be converted into 1 molecule of glucose:

    Cori cycle - Wikipedia, the free encyclopedia

    1 molecule of glucose yields 36 molecules of ATP via glycolysis when burnt aerobically.

    So, 1 molecule of lactate requires 3 ATP to convert it to half a molecule of glucose (equivalent to 18 ATP).

    So 1 molecule of lactate has the same calories minus 1/6 as 1 molecule of glucose. So lets say ballpark approx 80% of the calories by weight as glucose, as I can't be bothered to calculate the exact relative molecular masses right now.
    Last edited by paleo-bunny; 06-02-2012 at 01:54 PM. Reason: oops put lactose instead of lactate
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    Quote Originally Posted by paleo-bunny View Post
    It was indeed the Cori Cycle I was looking for and could not find, thanks a lot! That's a good starting point for my research. Now I have to understand if the lactate we eat, not the one we produce under anaerobic conditions, follows the same path. That would give an estimation of the real calories of yogurt.
    From what I see so far it seems that it may cause insulin release: lactate -> glucose -> glycemic index -> omg An explanation why the periods in which I eat more yogurt/kefir I am not in ketosis???

    P.S. I think you mixed the two words lactose and lactate, but not problem.

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    I feel special... I love yoghurt and the metabolic cycle for lactic acid yumminess is named after ME. Sweet.
    “You have your way. I have my way. As for the right way, the correct way, and the only way, it does not exist.”
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    And that's why I'm here eating HFLC Primal/Paleo.


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    Quote Originally Posted by primal_alex View Post
    Now I have to understand if the lactate we eat, not the one we produce under anaerobic conditions, follows the same path. That would give an estimation of the real calories of yogurt.
    From what I see so far it seems that it may cause insulin release: lactate -> glucose -> glycemic index -> omg An explanation why the periods in which I eat more yogurt/kefir I am not in ketosis???
    Assuming that you assimilate lactate from your digestive system, and there is no reason to believe otherwise, it would enter the portal vein on its way to the liver. Your liver would have no way to differentiate that lactate from the one produced endogenously in muscles when there is insufficient oxygen to process pyruvate in the Krebs cycle.

    Now, since lactate is produced by glycolysis in the muscles, I doubt very much that insulin would enter the picture because this would effect a net transfer of glucose from muscles that need it to tissues that do not, like adipose tissue, for instance, or other muscles that were not actively being used ( think quadriceps when you're doing pullups ).

    Insulin causes muscles cells to translocate GLUT4 glucose transporters from within the cell to the cell membrane where they can bind plasma glucose. Exercise does the exact same thing in a non-insulin dependent way. So, here is the scenario:


    1. You are cranking through some intense pullups, generating boatloads of lactic acid, feeling the burn, going for broke.
    2. Your lats, forearms, biceps are all screaming hoping for either more oxygen to be delivered, or glucose, and they've all sprouted GLUT4 receptors to try to soak up whatever is available in the blood stream.
    3. Your liver sees a bunch of lactate in the blood stream and starts extracting it to run that substrate through the gluconeogenesis cycle.
    4. The proceeds from hepatic gluconeogenesis hit the blood stream on their way to those hard working muscles.


    At this point, if there is a significant insulin response, that undermines the entire process as all insulin sensitive tissues will do their best to extract the glucose from the blood stream thereby essentially robbing the working muscles of what by all rights is their glucose as it is being produced from their lactate. If there is no significant insulin response, then only those muscle cells that are expressing GLUT4 due to exercise will extract glucose from the bloodstream, which is what we want.

    So, from a physiological point of view, I would not expect a strong insulin response from ingesting lactate, unless we are talking about massively supra-physiological levels. However, it is well known that dairy proteins are highly insulinogenic in and of themselves, quite independent of any carbohydrate contents, which might explain why eating yogurt knocks you out of ketosis, although that shouldn't be a cause for concern.

    -PK
    Last edited by pklopp; 06-02-2012 at 01:43 PM.
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    ^ agree - it's a big assumption that lactate will be assimilated from the digestive system at high concentrations.

    I also agree about the dairy proteins being a much bigger factor in generating a big insulin response. In addition, galactose from broken down lactose in yogurt is much more insulinogenic than glucose.

    I can't imagine that lactate is present in yogurt in sufficient quantity to have a significant effect on metabolism or blood sugar regulation.

    Have edited my typo above where I put lactose instead of lactate - thanks for spotting that, primal_alex.

    LOL - cori93437 you are indeed honoured.
    Last edited by paleo-bunny; 06-02-2012 at 02:13 PM. Reason: typo
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    Dear all,

    Thanks for your responses, very technical and informative. Really appreciated.

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