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Thread: Ketosis and mammalian diving reflex page

  1. #1
    Sungrazer's Avatar
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    Ketosis and mammalian diving reflex

    Ok, here is an idea I've been thinking about for some time now, I am not sure if I can put it out there eloquently enough or if I even are on to something at all. Please indulge me, and tell me what you think.

    We know that the mammalian diving reflex reduces the heart beat (by 10 - 25%) and blood is pulled away from extremeties and into the core of the body. Allowing the pressure to stay constant to avoid crushing the internal organs.

    From Wikipedia:

    When the face is submerged, receptors that are sensitive to cold within the nasal cavity and other areas of the face supplied by cranial nerve V (trigeminal) relay the information to the brain and then innervate cranial nerve X, which is part of the autonomic nervous system. This causes bradycardia and peripheral vasoconstriction. Blood is removed from the limbs and all organs but the heart and the brain, creating a heart-brain circuit and allowing the mammal to conserve oxygen. -- http://en.wikipedia.org/wiki/Mammalian_diving_reflex

    This added by the fact that a diet induced ketosis further reduces the need for the brain to use oxygen to burn glucose, but can use up to around 75% ketones for fuel. Could it be that a ketone adapted brain is adaptation to prevent hypoxia - as it doesn't mind so much if it is having less oxygen?

    Also a low carb diet allows the muscles to tap into fat for fuel, making the organism crave even less use of burning oxygen in the large muscles of the legs etc. Could it be that this is an evolutionary trait evolved to allow us to dive for food in cold and deep waters?

    Why have we retained this reflex? Is this why we have this reflex?

    I came to think about this when I was talking a cold shower and as the splash of cold water hit my face I immediately felt the diving reflex kick in. That, coupled with the aquatic ape theory, made my brain whirl.

    Any takers - anyone heard this discussed at all in scientific papers or anywhere?
    Last edited by Sungrazer; 05-24-2010 at 01:56 PM.
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    Wow. Watching the video right now. Still digesting. It would make sense that we evolved in an environment that provided seafood. More LC EFA = bigger brains.



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    I can't believe this is something I've never heard of. Biological Anthropology/Human Evolution Biology is topic in which I'm fairly well steeped.

    Wow.

    Nothing much to add yet. Still thinking.



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    Never heard of the Aquatic Ape theory, or my wild speculations? Here is a link on wikipedia about the aquatic ape theory: http://en.wikipedia.org/wiki/Aquatic_ape
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    Loved the video. *love*. I'm lab ratting right now for a researcher who discovered that progesterone is an effective tx for brain in jury. The most effective one there currently is. He first proposed his theory in the 60's and was nearly black balled from serious academia. He was tolerated though, while literally no one accepted his work. 30 years in, he'd published too much data for everyone to continue to laugh and ignore. Some interested docs in Emory's ER started doing research.

    Fast forward: Phase III clinical trials with a substance that is so safe, the NIH has allowed the bypass of informed consent. And it's cheap!

    Next up: Vitamin D and progesterone in combination because guess what? it appears to work better than the progesterone alone.

    It's hard to hear but easy to understand what Morgan means when she says "it's only not considered a viable alternative because of three words: 'Academia Said No' " Breaks my heart a little. Vitamin D scientists have been through it too, though there were more of them working on this and getting the word out.

    Protect III



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    I'm a marine mammal physiology PhD student, so I might be able to add a few interesting tidbits to this discussion.

    Most of the animals that make use of the mammalian diving reflex are, surprise, marine mammals. Marine mammals, for the most part, live on almost exclusively fat and protein (so, a diet similar to our PB), and yet are able to maintain a largely aerobic (oxygen-based) metabolism while holding their breath, etc. Their ability to do this is based, at least in part, on the diving reflex (lower HR leads to lower metabolism, less need for oxygen, etc.). The reason behind the peripheral vasoconstriction (movement of blood away from extremities and to organs) is mostly to maintain oxygen supply to the organs that MUST have it (i.e. brain, kidneys, etc.)...the blood carries hemoglobin, an oxygen transporter. The skeletal muscles don't need blood (as much) for the purpose of oxygen transport while diving...skeletal muscles have an analogue of hemoglobin called myoglobin, which allows oxygen to be stored directly in the muscles for use during aerobic activity.

    These diving marine mammals undergo hypoxia because they must hold their breaths under water (ofter for 90 minutes or longer), so I wouldn't say ketosis is an adaptation for hypoxia...but largely just based on the food that is available for them...the mammalian dive reflex may be an adaptation for frequent hypoxia, however. The reason we have this reflex is thought to just be a vestigial adaptation (i.e. one that may have been advantageous in the evolutionary past, but is no longer necessary).

    I teach human physiology labs, and we actually do an experiment every semester based on the mammalian dive reflex. If you're interested, the dive reflex works on any part of your body. I give my students the choice of using either their face or their foot for our labs...as long as you're holding your breath, both spur the reflex equally well.

    Don't know if that answered any of your questions...

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    Panthek - thank you for taking your time to answer my post. Very interesting, and it shows why laymen possibly shouldn't dabble too much in science, and let the scientists do that instead.

    Your post did however spur me on to search for some further information, and I found a few articles that is discussion diving reflex in better detail than I've found before. I haven't been able to read them through myself yet, but I will as soon as I can sit down in peace and quiet.

    Severe hypoxemia during apnea in humans: influence of cardiovascular responses
    http://diss.kib.ki.se/2002/91-7349-314-7/thesis.pdf

    This article does however puncture my idea pretty good, where it says:

    Carbohydrate depletion. Prolonged periods of physical work deplete the carbohydrate stores (glycogen) in the body, which forces the body to compensate by increasing the rate of lipid (fat) metabolism. When the human body burns fat to produce energy, it uses 8% more oxygen than when metabolizing carbohydrates. Also, 30% less CO2 is produced by fat metabolism. Thus a breath-hold hold diver who has depleted the glycogen stores will become hypoxic faster, and, making the situation worse, the CO2 driven stimulus to breathe will be delayed. A dive that could safely be performed in a rested and well-fed state may be dangerous after a long day of exertion from diving or land-based activities (50). Carbohydrate intake has been shown to reduce breath-hold durations, due to more rapid CO2 generation (because of a higher RQ) in subjects who had fasted for 18 h, suggesting that that the risk could be reduced by proper carbohydrate intake and that breath-hold diving on an empty stomach may be dangerous
    The physiology and pathophysiology of human breath-hold diving
    http://jap.physiology.org/cgi/content/full/106/1/284



    And finally this last one is a pretty interesting description of a hunting technique possibly also exploited by our early human ancestors (my speculation)?
    The Hae Nyeo of Cheju - breath-hold hunting
    http://www.divernet.com/Travel_Featu..._of_cheju.html
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    Very interesting, and it shows why laymen possibly shouldn't dabble too much in science, and let the scientists do that instead.
    naw, you *should* dabble. Good for the brain to try to wrap itself around some new, big, complicated ideas and connections.

    And you exposed me to something entirely new (aquatic apes theory). So dabble. Dabble away.


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    Quote Originally Posted by cillakat View Post
    naw, you *should* dabble. Good for the brain to try to wrap itself around some new, big, complicated ideas and connections.
    This is true - it's good to work the brain. Actually my only new years resolution has been "To learn something new each day" for some time now.

    Quote Originally Posted by cillakat View Post
    And you exposed me to something entirely new (aquatic apes theory). So dabble. Dabble away.
    Cool - glad to have tickled your brain as well!
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    Oh, and Panthek do you by chance know if ketones is produced in marine mammals in the same fashion as in humans? I would suppose so. I only found a brief reference to a urine sample taken of a minke whale that had traces of ketones in the urine.
    Sometimes you need to be told the truth in order to be able to see it.

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