Announcement

Collapse
No announcement yet.

Ask a biochemist.

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    1



    Truly awesome to have someone to explain stuff with some straight-up science! Here's a quicky: Is there any chemical explanation behind the CW that nutrients are more easily absorbed just after a workout (or just a scam by manufacturers of protein powder)?

    Comment


    • #17
      1



      @ NorthernMonkey


      1. There's quite a bit of controversy over vitamin D, and the science isn't all in on the issue. That being said, given that hunter gatherers the world around seem to go out of their way to eat foods high in vitamin D whenever they aren't making a TON themselves from sunlight, I'm strongly given to suspect that we benefit from high D consumption. That being said, I make sure to eat plenty of A along with my D, since a number of unpleasant things happen when one gets too low while the other is high.


      2. Oxalates aren't likely to make you fat. They are, however, stealing minerals from you that you'd otherwise like to have. In general, however, they're destroyed reasonably well by cooking, so I would just make sure not to eat too many raw, oxalate-containing foods if you're worried about it.


      3. I will be surprised if somebody doesn't find a compound which induces fructose malabsorption soon given all of the bad press fructose is getting. Imagine having lactose intolerance but for fructose. You'd kick your sugar habit in a hurry. If I had access to a high-throughput chemical screening lab...


      @ Timothy


      1. We store fat reasonably well in the absence of insulin (although certainly not as well), but we also burn it VERY readily in the absence of insulin. That's the more important part, in my opinion. Because of this, it's tough to "get fat" since you'll tend to just pull the fat out of your adipocytes and burn it (for heat or by inducing activity) rather than keeping it locked up. "Getting fat" is a largely hormonal event that involves your fat cells absorbing fats better than (and before) other parts of your body and then not giving them up.


      2. Sugar alcohols probably cause some slight disruption of gut floral balance and they also cause loss of adhesion to the intestinal wall. It would take a lot of them, however, to be much of a problem.


      That said, however, there are TWO ways that we sense the need for insulin, only one of which is dependent on blood sugar. The other is by starchy/sweet tastes in the mouth, which cause an initial "get ready" surge of insulin. This may or may not hurt your weight loss depending on how well your body responds to this insulin.


      @ Greg B


      1. You eat fat, which goes to the gut and is absorbed. The small and medium-chain fats go straight to the liver, completely bypass the carnitine shuttle which normally makes them wait in line and get rapidly metabolized into ketones for energy. These are tough to store, so you tend to just burn them for heat if you don't use them.


      Long-chain fats have more of a journey. They enter the lymph system in lipoprotein casings called chylomicrons and enter the blood, being delivered to a variety of tissues. If your body doesn't need them for energy, it stores them, but as I described above, it also accesses them very easily as long as insulin levels are low. This easy access means it takes any excuse to use them, making it hard to "get fat" eating fat. "Getting fat" requires that you completely overwhelm your body's ability to fritter away excess calories (which is quite substantial) OR that you cause a hormonal environment which makes withdrawals difficult, such as chronically elevated insulin.


      2. Yes, we do store some toxins in our fats. In general, we try to use enzymes like cytochrome p450 to make toxins A) less toxic and B) highly water soluble so that we can just excrete them in our urine, but when we are unable to do this for any of a number of reasons we do store them in our adipose tissue. Since glucose can cause highly undesirable glycation reactions in high enough concentrations (i.e. be toxic), we store it as fat instead of allowing it to circulate in large amounts.


      We also store some nutrients, but only the lipophilic (hydrophobic/fat-soluble) nutrients which can be stored that way. A, D, and K are the principal ones, although we may store some phytochemicals in our fat as well (this, actually, because they are toxins in large amounts as well). We also, of course, store energy in our adipose tissue.

      Give me liberty. Exploration of other options will be vigorously discouraged.

      Wondering something sciencey? Ask me in my Ask a Biochemist Thread

      Comment


      • #18
        1



        @ Pandadude


        Insulin sensitivity spikes post-workout for about 1-2 hours, remaining modestly elevated for some time after that. Since insulin is responsible for sugar and amino acid uptake by your muscles, greater insulin sensitivity means greater capacity to uptake nutrients. Other factors are at work as well, like increased blood flow to the muscles, but insulin sensitivity is the major culprit.


        That said, I wouldn't get too neurotic about post-workout eating. The benefit is pretty modest, and healthy, insulin-sensitive individuals will refuel their muscles just fine no matter when they eat.

        Give me liberty. Exploration of other options will be vigorously discouraged.

        Wondering something sciencey? Ask me in my Ask a Biochemist Thread

        Comment


        • #19
          1



          Greatest thread ever. So informative.

          Comment


          • #20
            1



            MG: re your reply on vitamin D. What of the recent research that suggest too much vitamin A negates the benefits you would receive from vitamin D? It's recently been on Mercola and I think even the Vitamin D Council spoke of it as well?


            Anyway, I'm heading into a science degree next year and just wondering if I should major in nutrition & nutraceutical science or biomed science. (Not doing biochem because the extra math I'd need - calculus - is not going to happen lol.) What were your favourite subtopics within the biochem category?

            Comment


            • #21
              1



              I have a question.


              Do you know of a study that shows as directly as possible that too much glucose causes insulin resistance? For instance, what happens if you constantly give a lab rat shots of glucose?


              BTW, I'm a biologist as well. Biochemistry was my favourite subject, but I hate the lab work involved. I've got no talent for it. Now I'm in neuroscience.

              Height: 5'4" (1.62 m)
              Starting weight (09/2009): 200 lb (90.6 kg)
              No longer overweight (08/2010): 145 lb (65.6 kg)
              Current weight (01/2012): 127 lb (57.5 kg)

              Comment


              • #22
                1



                MG, thank you for all the responses! This thread is gold. You've given me much to think about. I will be referring back here frequently.

                Comment


                • #23
                  1



                  @ Fabmandy

                  The studies cited in the vitamin D council report seem to support the idea that vitamin D and A can be antagonists, but only when one or the other is low. Low vitamin D status is associated with bad outcomes in many of the studies where A intake was moderate or higher, but the effect, by and large is small to the point of being highly dubious when D intake is high. In other words, both low is bad, but not way bad, both high still seems to be good.


                  Personally, I would recommend biomed science just because you're going to get a lot of BS in your nutrition classes and you need to understand the systems of the body in depth before nutrition makes sense anyways. I personally enjoyed my class on proteins and enzymes (folding, evolution, regulation, the works) enormously, but my enjoyment has come largely from what I'm now able to teach myself after laying the groundwork with basic chem and biochem classes.


                  Take all the general classes and then advanced classes in whatever interests you, but you cannot go wrong in pursuing proteins and how they function. Very important, and complicated enough to merit in depth study regardless of your interests.


                  @ Mirrorball


                  Annals of the NY Academy of Sciences Volume 967 Issue LIPIDS AND INSULIN RESISTANCE: THE ROLE OF FATTY ACID METABOLISM AND FUEL PARTITIONING, Pages 43 - 51 looks like a solid review of potential mechanisms (I can't tell because my login to my university journal subs is failing at the moment). It's pretty well established that prolonged hyperglycemia causes insulin resistance, it's just not clear why. It should be born in mind, however, that a single bolus of glucose doesn't do this and also that prolonged hyperglycemia isn't the sort of thing which happens when people eat a natural diet.

                  Give me liberty. Exploration of other options will be vigorously discouraged.

                  Wondering something sciencey? Ask me in my Ask a Biochemist Thread

                  Comment


                  • #24
                    1



                    Thanks a lot! I can't get the article from home either, not even when I connected to my university's network. I'm going to try downloading it from the lab tomorrow.
                    [quote]

                    prolonged hyperglycemia isn&#39;t the sort of thing which happens when people eat a natural diet</blockquote>


                    Not even people on the SAD? What about diabetics?

                    Height: 5'4" (1.62 m)
                    Starting weight (09/2009): 200 lb (90.6 kg)
                    No longer overweight (08/2010): 145 lb (65.6 kg)
                    Current weight (01/2012): 127 lb (57.5 kg)

                    Comment


                    • #25
                      1



                      Could you discuss the basic structure of insulin receptors and why prolonged exposure to insulin, such as on a high carbohydrate diet, leads to insulin resistance?

                      Comment


                      • #26
                        1



                        By natural diet, I mean diet that isn&#39;t high in agents which damage regulation of glucose disposal. The Kitavans, for example, eat LOTS of glucose, but not very much fructose, no wheat, and very little n-6 PUFA which is easily balanced out by their fish consumption. We can quibble about the fact that many (not all, mind you) smoke, which activates Lipoprotein Lipase, but the fact of the matter is that their blood glucose spikes and is quickly brought back down to a baseline rather than remaining chronically elevated. You are unlikely indeed to get chronic hyperglycemia regardless of your macros as long as long as you keep it paleo.

                        Give me liberty. Exploration of other options will be vigorously discouraged.

                        Wondering something sciencey? Ask me in my Ask a Biochemist Thread

                        Comment


                        • #27
                          1



                          This is Nerd heaven, thanks Grokologist.


                          I am currently interested in two broad issues:


                          a) "This is your brain on (mostly)ketones" (vs. glucose)

                          b) The "repair" metabolic pathways supposedly triggered by Intermittent Fasting.


                          "a" caught my attention after noticing that I feel way sharper while on ketosis, and due to many papers recommending a ketogenic diet in children who suffer from seizures.


                          "b" I find fascinating. There&#39;s lot&#39;s of research linking caloric deprivation with longevity in monkeys, for example. I am not sure to what extent this research applies to humans, but I would think it does significantly. I.F. would "trick" the body into thinking we are suffering from caloric deprivation and hence trigger these repair mechanisms. Or maybe it&#39;s not caloric deprivation but the opposite of feeling "satiated". I don&#39;t know.


                          Anyway, very interesting posts, thanks for the read.

                          “Every saint has a past and every sinner has a future.” -Oscar Wilde
                          "The power of accurate observation is commonly called cynicism by those who have not got it." -George Bernard Shaw
                          "The trouble with jogging is that the ice falls out of your glass." -Martin Mull

                          Comment


                          • #28
                            1



                            Oh I am also fascinated by propioception/kynesthetics and it&#39;s impact on stress.


                            It would appear that certain types of propioceptor feedback would play a role on inducing stress. This would help explain the benefits behind yoga, for example...

                            “Every saint has a past and every sinner has a future.” -Oscar Wilde
                            "The power of accurate observation is commonly called cynicism by those who have not got it." -George Bernard Shaw
                            "The trouble with jogging is that the ice falls out of your glass." -Martin Mull

                            Comment


                            • #29
                              1



                              I take heart from any mention of the Kitavans, as I just can&#39;t adapt to VLC. I eat a fair amount of carbs, but all from fruits and vegetables. Perhaps I&#39;ve never been very insulin resistant, because I&#39;ve been able to lose weight just fine. Thanks again for all the information in this thread.

                              Height: 5'4" (1.62 m)
                              Starting weight (09/2009): 200 lb (90.6 kg)
                              No longer overweight (08/2010): 145 lb (65.6 kg)
                              Current weight (01/2012): 127 lb (57.5 kg)

                              Comment


                              • #30
                                1



                                What an interesting and informative thread! Thank you, Molecular Grokologist, for spending all this time responding to questions. I&#39;m learning a lot, as I&#39;m sure are others.

                                Comment

                                Working...
                                X