If you made it through the encyclopedic posts that were part 1 and part 2 of this series on insulin, and you’ve come back for more, thank you! It is one of my biggest flaws as a writer: brevity is not my strong suit. (But at least I admit I have a problem. That’s the first step, right?) This post is no exception. In fact, it's probably longer than the first 2. So go grab a cuppa joe, or tea, or whatever you like, and hunker down for a nice, long read.
Okay. So I left off last time pointing out that, in covering the effects of elevated insulin and glucose on the cardiovascular system, reproductive function, the brain, kidneys, eyes, and inner ear & balance mechanisms, I had not said one word about obesity. I hope we’re all on the same page and can agree that insulin resistance is not something limited to people who are carrying around a few—or a couple hundred—extra pounds. Obviously, there are millions of non-overweight people who are infertile, have heart disease, kidney disease, vision problems, dementia, and more. (I have written about this before. One of my personal favorite posts on this entire blog is the one where I explained that obesity is simply one more effect of metabolic derangement, rather than its cause. I also wrote about this topic for Designs for Health.)
Nevertheless, we’d be missing a substantial piece of the insulin puzzle if we didn’t talk about the role of insulin in regulating body weight. Before we get to that, however, we first need to look at the actual functions of insulin, as well as the pancreas. It is an unfortunate byproduct of our epidemic of “diabesity” that we automatically think of blood glucose when we hear the word insulin. And there’s no doubt insulin does have an important role in regulating—or, more specifically, lowering—blood glucose (BG). But that’s not insulin’s only function. In fact, I would argue it’s not even the primary function. We will get to weight, I promise. But just like we did in the cancer series, we’ve got to trudge through a lot of biochemical weeds before we get to the good stuff. So here goes.
Physiological Actions of Insulin &
|Chart courtesy of Charles Saladino, PhD, Misericordia University|
As you can see, there are three hormones—three—whose job is to raise blood glucose (BG), and just one—one—whose job is to lower it. Right off the bat, this hints at something: the human body may have been conditioned in an environment in which there was likely a frequent and/or immediate & crucial need to raise BG, and much less of a need to lower it. This suggests that our BG wasn’t running super-high all that often, considering there is a triplicate redundancy in mechanisms for raising it, but only a single point of failure for lowering it. (Hormonally speaking, that is. I’m not forgetting about non-insulin-mediated glucose disposal, which is a nice benefit of intense exercise.)
I’m not claiming that the evolutionary/ancestral health perspective is correct 100% of the time, nor that it is the only thing we should consider when trying to make sense of things. I do believe, though, that it provides a handy framework to guide us in assessing things logically and intelligently, and that we can look to the anthropological record to try and find answers for some of our modern ills. For example: our ancestral diets were likely far less insulinogenic than our modern, grain-heavy one is. Even if Paleolithic man—or whoever you want to look back to as your individual ethno-geographic dietary ancestors—ate some small amount of grain in addition to a generous supply of tubers and seasonal fruit, overall, the glycemic load and insulin-raising effects of the total diet were probably very small. And these hominid ancestors may have had a need—not constantly, but often enough—to run away from predators or to chase prey, which would have necessitated an immediate way to raise blood glucose. And because the raising of BG at a critical moment would have literally been a matter of life or death, it makes sense that the triple redundancy is there. It is only in the modern world, where cortisol and adrenaline (epinephrine) are high all the time in some people, where this constant flooding of the blood with glucose gets us in trouble—particularly when combined with a high-carbohydrate diet. Back in the day, getting BG up at the appropriate time was lifesaving. Today, however, keeping BG (and insulin) up all the time is quite literally killing us.
Okay, so there are three hormones that raise BG, while insulin lowers it. And the blood glucose lowering effect of insulin is quite important. Ask a type 1 diabetic if insulin is “toxic,” and you’ll probably get a very different answer than if you ask a nutritionist in the LCHF/keto camp. Insulin is not toxic. It is a damn handy hormone to have—when your body responds to it properly. In fact, insulin, itself, is a lifesaving hormone. The development of synthetic insulin to help type 1 diabetics was nothing short of a miracle. People who were at death’s door could now lead long, healthy, productive lives. There is most definitely a role for a low-carb diet for type 1 diabetics, but even those following a LCHF diet will still require some insulin. (Just far, far lower doses than they typically need on a high-CHO diet.)
Because insulin injections were nothing short of lifesaving for T1 diabetics, we can forgive the early pioneers of treating diabetes for assuming they would be equally beneficial for T2 diabetics. After all, if insulin lowers blood glucose in T1 diabetics, and T2 diabetics have high BG, then it stands to reason that insulin will help T2 diabetics as much as it does T1s. Problem solved, illness cured, right?!
Unfortunately, as we now know, the therapeutic use of insulin for type 1 diabetes does not translate to type 2 diabetes.
What mainstream endocrinologists don’t seem to realize is that BG is elevated in T1 diabetics and T2 diabetics for completely different reasons. In T1Ds, it’s because they produce little to no insulin. In contrast, T2Ds produce plenty of insulin. They’re awash in it. Their cells are practically drowning in it. The problem is, their cells have stopped responding properly. It’s like the story of the boy who cried wolf: do it over and over and over again, and eventually the villagers stop paying attention. In T2D, insulin is knocking, but no one’s home. T1 is insulin deficiency, while T2 is insulin resistance in the face of insulin excess. (There may come a time, when someone has very advanced, very longstanding T2D, that their pancreatic beta-cells actually call it quits and they don’t produce much insulin. This is called “beta cell burnout.” Obviously, that’s not the scenario we’re focusing on here. I just want to acknowledge that it can happen. Also, it is as yet undetermined whether chronic hyperinsulinemia causes insulin resistance, or if cells become insulin resistant first, resulting in hyperinsulinemia. Which is the cart, and which is the horse?)
Another clue that T1D and T2D are different pathologies is that an untreated T1 diabetic will have sky-high blood glucose along with sky-high ketones. (Sky-high ketones are the result of the uncontrolled catabolism of their adipose tissue. This is ketoacidosis, which is a completely different state from diet-induced nutritional ketosis.) T2 diabetics, on the other hand, will have sky-high blood glucose without sky-high ketones. Why? Because they produce tons of insulin, and insulin inhibits lipolysis. Let’s say that again: Insulin inhibits lipolysis. (With lipolysis being the primary source of ketones.) We’ll come back to this next time, when we talk about body fat regulation. T2 diabetics can experience ketoacidosis, but it's far more common in T1s.
Giving insulin to a type 2 diabetic who already secretes too much insulin is like the misguided prescribing of antacids to individuals who have low stomach acid. If doctors would measure the HCl activity of patients who complain of GERD, heartburn, and general indigestion, they would see that the majority of these folks don’t have excess stomach acid; they actually have too little! And if doctors would measure a T2 diabetic’s insulin levels, the way Dr. Kraft did with so many patients, they would see that they have too much. And, in following the anointed standard of care, they would have to reconcile the wisdom of giving these people even more insulin. Maybe making the insulin assay a part of a regular checkup would finally wake modern medicine up to the idea that type 2 diabetes is not an insulin deficiency.
Endo-, Exo-, and Paracrine
Okay. Now that we’ve entered the territory of lipolysis and ketosis, it’s time to dive a little deeper into the physiological mechanisms of insulin and other blood glucose regulating hormones, as well as take a closer look at the pancreas.
With all this blood glucose talk, it would be easy to think that your pancreas has one job, and one job only: to secrete insulin. On the contrary, this is just one of many functions this precious organ performs. The pancreas is an endocrine, exocrine, and paracrine organ. As an endocrine organ, it secretes hormones into the blood. As an exocrine organ, it secretes substances into a duct. As a paracrine organ, it secretes substances that act on itself. (Specifically, certain cells of the pancreas secrete hormones that act locally, i.e., on other cells of the pancreas.) Here’s how this works:
(1) Remember from way back in the series I did on digestion, that the pancreas is a major player in helping your body break down food so you can absorb all those great nutrients from your
caramel pecan cheesecake grass-fed ribeye and organic asparagus. The pancreas, itself, doesn’t digest anything. What it does is secrete several enzymes into the small intestine, and it is the small intestine that actually does the work of digestion. Pancreatic digestive enzymes (which include enzymes that break down protein, carbs, and fat) make their way to the intestine via the pancreatic duct. This is the exocrine function of the pancreas.
(2) The specialized beta cells of the pancreas secrete insulin into the blood, and the alpha cells secrete glucagon into the blood. This is the endocrine function.
(3) Insulin and glucagon travel through the bloodstream to exert their effects on target cells all over the body, but they also act locally, on the pancreas itself. This is the paracrine function. This is a big deal. Bigger than big. It’s huge, in fact, and I didn’t even realize how huge until about two weeks ago. More on this at the end of the post.
The digestive/exocrine function is not relevant to the topic at hand, so we’ll leave it aside. Let’s look at the endocrine function. When a healthy, non-metabolically derailed person consumes carbohydrates, their blood glucose goes up a little bit, and insulin is secreted to bring it back down. On the other hand, if it’s been a while since this person has eaten anything, the pancreas secretes glucagon. Recall from the hormone chart above that glucagon maintains blood glucose levels during fasting—or, really, just between meals, after insulin has returned to its low-ish baseline. Glucagon is what keeps blood glucose from plummeting to dangerously low levels if it’s been, say, 14 hours since your last meal.
Glucagon is a fascinating hormone. It’s the Rodney Dangerfield of hormones; it gets no respect. And that is a shame. The truth is, glucagon is such a huge player in all this that, upon learning more about it, I was worried I had done you all a disservice, because I should have called this series “It’s the Glucagon, Stupid.” But then, when I learned even more, I felt reassured, because it is really about the insulin. (Shut up, Amy. No one cares. Get back on topic.)
|Insulin, glucagon, and blood glucose:|
the ultimate balancing act.
Something else that stimulates glucagon is ingestion of protein. This is where things get interesting. The seasoned low-carbers among you know that protein stimulates insulin. (This is a good thing. This is a big part of how we build muscle mass; insulin helps escort amino acids into the cells. It’s also why you don’t absolutely need carbs post-workout. The protein will raise insulin all by itself.) Some of you low-carbers who aren’t quite as familiar with the ins and outs of all this might have heard somewhere that protein “spikes blood glucose.” You might have also heard people saying that, in terms of blood glucose regulation, for some people, a big whack of protein is as bad as chocolate cake, and for this reason, people on low-carb diets for the specific purpose of keeping blood sugar low should be careful not to overconsume protein.
I am not arguing that ingesting protein doesn’t raise blood glucose. (It does.) And I’m not arguing that certain amino acids aren’t strongly glucogenic. (They are.) BUT: let’s see how this actually works, because steak and chicken are not chocolate cake, okay?
Let’s look at this through our evolutionary lens. Let’s say your tribe has just had a good kill. And let’s say you’re somewhere down toward the middle of the tribal hierarchy. Maybe the higher ranking males and females have first dibs, and they chow down on the organs, the entrails, and some of the other prized pieces of this prey. By the time it’s your turn to lop a piece off with your handy stone tool, maybe all that’s left is a big ol’ piece of muscle meat—and a relatively lean one, at that. But this isn’t 2015 in the U.S., and there’s no baked potato, buttered roll, and soda to go with your meat, so your meal is meat, and nothing else. Lots of protein, a little bit of fat, and virtually zero carbohydrate.
If you were to eat this piece of meat, and the protein raised insulin (as it does), not only would the amino acids go from your bloodstream into your cells, but plenty of glucose would go along with them. Now, being that you are a Paleolithic “person,” let’s say your blood glucose is cruisin’ somewhere around 75. But now, thanks to your piece of meat, you have an insulin rise in the absence of dietary carbohydrate. Without a counter-regulatory hormone, your blood glucose could get too low. (Assuming you’re not overtly ketogenic, that is. You can have what would otherwise be considered freakishly low BG but feel completely fine if your ketones were high enough.) So thank goodness there is a counter-regulatory hormone, in glucagon. Sorry for this little digression; I just figured that, for some of the lay readers out there, who might not know about all this, this would be a good way to explain why dietary protein stimulates both insulin and glucagon. It’s quite nifty, how nature does this.
SO: I don’t think it’s correct to say that eating a large whack of protein “spikes blood glucose.” I think what it does is stimulate glucagon, which raises blood glucose in order to counteract the glucose lowering effect of insulin. This is totally normal, and no problem whatsoever—FOR A METABOLICALLY HEALTHY PERSON. (And it's why plenty of low-carbers don't need to deliberately limit protein intake.) But let’s see what happens in a metabolically UNhealthy person—specifically, someone who is insulin resistant.
It could be the glucagon, stupid,
but really, it’s still the insulin
Insulin resistance occurs when cells no longer respond to the presence of insulin. We know for sure that muscle cells can become insulin resistant. But you know what other kinds of cells can become insulin resistant? THE GLUCAGON-SECRETING ALPHA CELLS OF THE PANCREAS. Yes! Now we’re getting somewhere.
It’s time to examine the paracrine function of the pancreas. Recall from the hormone chart way above that glucagon mobilizes fuels. It activates gluconeogenesis, glycogenolysis, and lipolysis. We know glucagon does this. This is how it keeps blood glucose at a safe (i.e. high enough) level between meals or during a longer fast – it catabolizes existing muscle tissue to get at some glucogenic amino acids, and it stimulates the breakdown of down glycogen into individual glucose molecules. It also stimulates lipolysis—that is, the breaking down of stored body fat, the glycerol portion of which can be used to make glucose. Now that we see what glucagon does, we can have a much better understanding of type 1 diabetes. T1D is glucagon run amok in the absence (or deficiency) of insulin. Untreated, type 1 diabetics remain in a perpetual state of catabolizing their own bodies in order to be fueled. They break down their muscles, they break down their adipose tissue, and, eventually, they’ll break down their organs. You can see why, in the absence of insulin to counteract the glucagon, T1 diabetics might be emaciated.
Here is something absolutely fascinating about the paracrine pancreas. Before entering the general blood circulation, the insulin that is secreted by the beta cells works directly on the alpha cells. The alpha cells are insulin’s first stop before it travels to the rest of the body. Basically, insulin tells the alpha cells to stop churning out glucagon. BUT: the amount or concentration of insulin that hits the alpha cells is much, much greater than the concentration of insulin than the rest of the body responds to. It’s almost like, in tamping down the alpha cells, most of the insulin is siphoned off, so a much lower concentration is left for the rest of the body. This is what is supposed to happen. And this explains why it is so difficult for type 1 diabetics to manage their blood sugar. If they were to inject themselves with insulin at the strength needed to suppress glucagon, it would completely overwhelm the rest of the body and certainly induce a life-threatening “low.” In a best case scenario, the amount of insulin they inject is matched to the amount of carbohydrate (and protein) they eat. But this does not at all take into account the extremely concentrated amount the alpha cells require in order to stop secreting glucagon. So you can see now why T1s have BG that is all over the map.
Okay, back on message. In a healthy person, glucagon’s catabolic effects only dominate when insulin is low—between meals and during a fast. For someone on a low-carb diet, glucagon will be somewhat active all the time, but in the fed state, it will be mostly overridden by the presence of insulin—yes, even just the relatively small amounts of insulin a low-carber would secrete. In a type 1 diabetic, glucagon dominates all the time. This is why they waste away without exogenous insulin, and also why they have concomitantly high glucose and ketones. In a metabolically healthy person, even small amounts of insulin are enough to limit the effects of glucagon. (This is the beauty of a low-carb diet in a healthy person: BG that is neither too high nor too low. I emphasize again: insulin is not toxic. Insulin is great, provided your body knows what to do with it.)
I said earlier that T1D is glucagon run amok, because there’s no insulin to shut off that signal. Oddly enough, for many type 2 diabetics, their condition is also glucagon run amok, but it’s obviously not because there’s no insulin. There’s a ton of insulin; many cells just don’t care anymore. And remember: among the cells that don’t care anymore are the glucagon-producing alpha cells. Because the alpha cells are insulin resistant, they function as if there is no insulin. That is, they continue to hemorrhage glucagon. So, even when blood glucose is high, such as after a high-carb meal, glucagon can raise it even higher. The carbs would have raised BG, and therefore, insulin, but because the alpha cells no longer sense the insulin there, they will continue to pump out glucagon as if a high-carb meal had not been ingested. And what will this glucagon do, but continue to raise BG even more, by breaking down existing muscle tissue to get at the glucogenic amino acids? (Remember, though, that even with sky-high glucose, hyperinsulinemic T2 diabetics might not generate lots of ketones, because, in a cruel twist of fate, the adipose tissue still seems to be sensitive to insulin, and insulin inhibits lipolysis.)
|As bad as soda? Come on.|
And remember: protein elevates both insulin and glucagon. THIS is why people who are extremely insulin resistant are well-served not to “overconsume” protein. (Whatever that means, anyway. The threshold is an individual thing.) If they are eating “too much” of a food that raises glucagon, and, by extension, blood glucose, but they cannot clear that glucose out of the blood due to insulin resistance, this is a kind of double whammy.
I suspect these forces were at work in my own mother, who had poorly controlled T2D. (Read about her unfortunate and hapless medical care here.) She was on insulin, and her blood sugar was completely unpredictable, regardless of what she ate or her insulin dose.
It’s interesting to note that, among many overweight T2 diabetics, they are “large,” but they don’t seem to have much muscle mass. With what we just covered, we can speculate that maybe they have less muscle because their bodies are so good at breaking muscle down. As for how they end up heavier, when someone is severely insulin resistant (and remember, this goes for their alpha cells), I suspect it works like this:
Elevated glucagon --> catabolize muscle
Elevated insulin --> do NOT catabolize stored body fat
Boy, is that a horrible scenario to find one’s self in: break down your extremely valuable muscle tissue, but nope, don’t touch any of that fat! Leave it right where it is! In fact, make more!
Okay, since I’ve finally—finally—circled back to the topic of body fat, this is a good place to end for now, and we’ll start right back here next time.
In the meantime, if you’d like to learn more about all this glucagon stuff, I cannot recommend this video highly enough. I wasn’t kidding when I said I had just learned a lot of this recently, myself. Most of it came directly from this video. (Thanks again to Ivor Cummins for letting the rest of us know about it.) I am not ashamed to admit I was absolutely FASCINATED. RIVETED. Here was my reaction:
Just had my MIND BLOWN about 15 times watching this video, re: insulin & glucagon. A must, must, *MUST SEE!* http://t.co/ddvU9DUPi0— Amy Berger (@TuitNutrition) September 21, 2015
You, too, will have your mind blown. Guaranteed. (Especially when Dr. Unger talks about the concentration of insulin as it exerts its paracrine function on the alpha cells. Seriously, WATCH IT!)
Continue to part 4 in this series: http://www.tuitnutrition.com/2015/10/its-the-insulin-4.html
Remember: Amy Berger, M.S., NTP, is not a physician and Tuit Nutrition, LLC, is not a medical practice. The information contained on this site is not intended to diagnose, treat, cure, or prevent any medical condition.