Transcription
Hello and welcome to the Metabolic Classroom, where we dive into the science behind metabolic health. I'm Benjamin B. Berman, metabolic scientist and a professor of Cell Biology. Today, we are exploring continuous glucose monitors, or CGMs. These small devices with an increasingly huge impact and popularity, especially among those who are just looking to get some real-time insights into what's going on in their bodies with regards to metabolic health, as that is impacted by glucose levels.
Now, in the episode today, I want to cover some material that shows that CGMs aren't just for people with diabetes. Not anymore. And maybe, I would say, they never should have been. These tools really are powerful for people who are wanting to get a better understanding of their own metabolic health, but it also has some tremendous clinical utility, helping people perhaps understand where they are with regards to some particular metabolic diseases. So, we'll explore some of the evidence suggesting that CGMs can detect early signs of pre-diabetes and diabetes, uh, and particularly relevant and important in people who don't know. Um, so that's, we'll go through first. That's just a general overview of the structure of, of today's lecture.
All right, so let's start by just defining, uh, continuous glucose monitors. So, basically, these are small devices that are often placed on the back of an arm or on the abdomen, and it has a small little probe that gets inserted just beneath your skin. And it's technically not measuring your blood glucose. This little probe isn't going into your blood vessel. It's measuring the interstitial glucose. So, briefly, you have the blood vessel. If we're looking down the length of a blood vessel, that glucose has to get from the blood vessel, out of the blood, into the cells that are surrounding the capillary. That's the smallest kind of, that's the business unit of the blood vessels. So, we have the glucose that is moving from the, uh, from the plasma or the blood into the space surrounding the blood vessel. That's where this little probe is, and so that's what you're getting measured.
Now, of course, unlike traditional finger pricks, which used to be the way of measuring blood glucose, um, that would only provide a single snapshot of where your glucose is. CGMs, of course, are continuous. It's giving you the opportunity to have a constant readout of your blood glucose, day and night. Now, of course, initially, CGMs were developed for use by people with diabetes to help them manage their insulin injections and their insulin dosing, to prevent them from going too low or too high. But, of course, as I'm going to prove to you, I hope, based on multiple published papers, CGMs are increasingly used by non-diabetic individuals to just allow them to gain insights into how their body is responding to various stimuli, food included, but also exercise, stress, sleep disturbances, uh, and more.
Now, how do they work? I already mentioned the little filament or sensor that gets embedded. There's that little poke when you first put the CGM on. And then the device, the CGM will transmit its data to an app that's typically on your phone. Although a person who doesn't have a smartphone can also just get a CGM reader, that is a separate little handheld device that will tell you the number. All right, so, so that's what CGMs are and their historic use.
Now, let's talk about some of their utility. So, CGMs have brought to light a fascinating concept: each person has unique glucose responses to the same foods. So, a meal that might spike one person's glucose can have little impact on someone else's. There are a couple of studies that I want to highlight. I'm going to spend most of my time on a study that I consider to be one of the coolest. It was, it's a study published out of, uh, University in Israel and was published in 2015. This was, um, firstly, a pretty good-sized group. They had 800 participants in the study, and they consumed identical meals under very well-controlled laboratory conditions. The scientists who put the project together found that the glucose responses varied widely from person to person, even when they ate the exact same foods at the exact same time of day. So, they were very thorough in controlling for these obvious potential confounding variables.
What they found, for example, was that in some people, some foods that typically would be labeled as healthy, or others perhaps unhealthy, based on their glycemic load or how much they would be predicted to affect glucose, might not have that same effect. That, even though it was predicted to have an increase in blood glucose, it wouldn't necessarily. So, some people, for example, maybe would see a greater glucose response to foods like whole wheat bread, while others would have a much larger response to something like a piece of fruit or rice.
Now, this is a bit of a tangent, but I have to, I can't leave this unmentioned because it was such a pivotal part of this study, um, and that is the role of the microbiota, the, or the microbiome, the bacteria in the digestive tract. The researchers discovered that the gut microbiome composition, so the actual type of bacteria a person had, played a significant role in determining how the individual responded to different foods. They found that specific microbial profiles, or different populations of bacteria, were associated, could be used to predict the higher or lower glucose responses. Um, now, then collectively, based on all of that data, the team was actually able to create an algorithm that could predict an individual's blood glucose response, as measured by a CGM, based on their microbiome. So, in other words, analyzing their microbiome and other factors like, um, BMI, some various blood markers, including those of insulin resistance, they could then say, "Okay, you're going to be a person who responds with a high glycemic response to this food, and a very modest glycemic response to this other."
So, I mentioned, I sort of alluded to an example earlier, um, to be very precise about it, um, some participants experienced low glucose responses with the CGM to foods that were traditionally considered high glycemic, like ice cream. And the same person might have a very low response to something that would have been, um, also considered high, like, like rye bread. Now, all of this is to say, the study highlighted, highlights that the standard glycemic load of foods wasn't consistent. That it really was individual, based on a variety of factors, including the microbiome. But it is further evidence of the utility of a CGM in allowing someone to know, "How am I responding to this specific food that I'm eating right now?" So, that real-time response, the real-time feedback, um, is tremendously useful. It, in this, in the case of the study, it helped many of the participants reduce their glucose variability. So, they were able to make their own changes and turn a glucose level that was going like this, with all this noise, into a much quieter signal.
Now, another paper was published, and I won't go into as much detail, um, because it's a little simpler. It's a, a paper that was published out of Stanford University that is just abbreviated as the DIAMOND study in 2017. They found that using a CGM allowed individuals to see hidden glucose spikes, um, so responding with a high glycemic load or, or blood glucose response, even when it was unexpected based on what they were eating. So, this plays a little bit into, uh, following up somewhat, although be it with less precision compared to the study out of Israel, um, but nevertheless, they note that those with the visible glucose spikes could identify and modify the foods they were eating or the habits that triggered them, demonstrating once again that CGMs are valuable beyond just traditional use in diabetes, just the explicit measurement of glucose in order to understand how much insulin needs to be injected. Okay, so these are a couple of studies among many others that I'll just highlight for the sake of time that suggest or reveal that CGMs can be a very useful tool, helping people gain insight into their personal responses to what they eat.
Now, I'd alluded in the introduction to the fact that CGMs also have a tremendous clinical use. Everything I just described is their use in an individual wanting to gain insight into their unique metabolic responses to food. I believe that insight is tremendously valuable, and that alone, I think, justifies the widespread use of CGMs. But I, I do want to go a little more clinical. So, just by way of setting the background and relevance of this, about one in three Americans has pre-diabetes. In fact, I would suggest that it's even higher than that. Um, but the vast majority, estimated that up to 80% of them don't know. Now, that's separate. That's just pre-diabetes. There are many people, of course, as well, who have actually full-blown type 2 diabetes but don't know it because they haven't gotten tested for it. All right.
Now, CGMs, in this case, can be very helpful at catching these conditions early because they reveal the glucose patterns that would go otherwise unnoticed. All right, so one paper of two that I'm going to highlight, again, just to keep things balanced and for the sake of time. This paper was published just a few years ago out of the Scripps Research Translational Institute. So, this had 300 people using CGMs, and the research group found that nearly 15% showed glucose patterns consistent with pre-diabetes or outright type 2 diabetes, even though they had not ever been told and had never been diagnosed. So, 15% of these subjects in this study actually had a diagnosed, a diagnosis at the end of the study, based strictly on the use of the CGM. So, clear evidence that a CGM has, uh, tremendous value as a screening tool for people who are at risk but don't know it, indeed at sufficient risk that they actually have the problem.
Also, the famous Framingham Heart Study, which has gone on for tremendously long period of time, several decades now, just a few years ago, had a substudy that used CGM in about 2,000 participants. And so, they had these participants that were classified as healthy based on the conventional metrics, but they once again showed patterns indicating undiagnosed pre-diabetes. So, this was a very large, famous study, once again showing the same thing. Um, early findings, uh, suggesting here that the CGMs are detecting these irregularities, allowing the person to make some changes or have a clinical intervention to prevent them from getting worse.
Now, traditionally, people are often only relying on annual glucose tests. That's just measuring fasting glucose or A1C levels. Um, but again, that's just a single snapshot. And moreover, it is possible for someone to kind of prep for those kinds of annual tests if they're even going in annually. And let's admit it, most people aren't going in for an annual wellness visit. Um, but the CGM, by allowing the individual to have some insight into their dynamic response, so what's happening when they actually are eating something, um, that provides much more insight than you can get from just a singular snapshot of a fasting glucose.
Okay, now I have been presenting the case that CGMs are just universally helpful and thus ought to be democratized in their access. Let them use CGMs, we would declare. However, there are people whom I respect, um, who are naysayers of this. That they think that CGM should never be used outside of the context of diabetes. That if you are not diabetic, don't touch it. Now, this importantly is not due to, uh, limited access. That, in other words, non-diabetics using CGMs are preventing diabetics from getting them. That has never been the concern, and there's no evidence that that's the case. That would be low-hanging fruit as a critique to say, "You're again, you are taking that CGM that would have otherwise gone to a diabetic." No, there's no, there's no restriction. Um, that's not the limit. That's not the reason. People, if anyone's citing that, they're not justified in citing it. But nevertheless, so while CGMs are getting more popular, I would say rightly so, um, I think it is fair to look at some of the common critiques and why these concerns may come up at all.
So, first critique: one, lack of evidence for long-term benefits in non-diabetics. So, a critic will argue that CGMs can show glucose fluctuations, um, but there's limited research proving that these, that the fluctuations have any significant long-term benefit in monitoring if you don't have diabetes. Um, that it just might lead people to obsess over the numbers without some clear link to their health. My counter to that would be, why then, if, if it isn't, let's say, a type two diabetic who's not on insulin therapy, do the glucose fluctuations matter to them? Yeah, of course. But why does it not matter then to someone who hasn't been formally diagnosed?
Critique number two is that it's, there's an overemphasis on glucose. That it might, people, it might make people, uh, focus unnecessarily on glucose, which could lead to an unhealthy fixation on just what they're eating and this desire to avoid any degree of glucose spike at all. People are increasingly saying, "There's nothing wrong with a glucose spike." I agree, in general, although I don't, it's not as benign as people would like to think. In fact, I invite you to look at a previous Metabolic Classroom where I talk about hypoglycemia. There are consequences even to an acute glucose spike, like glycation. And even though the glucose may come down well, uh, what has happened to the insulin? How long has insulin had to go up, and how high did it have to go? While the glucose may have gone up and down in 90 minutes, the insulin certainly hasn't. And the insulin may be up for three to five hours. And again, what if, if it was one individual glucose spike every day, even I would say that's pretty benign, if not totally. But that's not how it happens. People spike it often, and it is the frequent spiking of glucose leading to frequent rises in insulin, and that combination is a perfect metabolic storm.
Another issue is cost and accessibility. The costs of CGMs can be high, and they're not always covered by insurance if it's non-diabetics. Um, however, a counter is that that is, leave it to the free market and capitalism to find a solution for a problem. There are increasingly more affordable options and ones that are available over the counter. So, I imagine that that technology is going to continue to make CGM or continuous glucose monitoring, whether it's the stick-on device or some other kind of wearable, that access is going to continue to go up while the costs are going to continue to go down. Um, there's also some other, I would say, more vague concerns, like there's a psychological impact that it, people seeing their glucose spike may make them anxious. Maybe, maybe. But I would say it's important, uh, to, you know, maybe you need to be a little anxious, maybe a little more anxious about what you're eating in order to improve your metabolic health. Maybe you've been too indifferent to it. Okay, so those are some of the main criticisms. While I respect them, or at least the source of them, these individuals who are critical of CGM, um, I do think that the benefit, that the benefits outweigh those potential concerns.
Okay, now let me, speaking of benefits, um, as we are actually nearing the end in a relatively shorter Metabolic Classroom today, um, let's talk about just some final benefits. So, one being the improvement in insulin sensitivity by reducing glycemic variability. Because CGMs can help users recognize these glucose fluctuations and know, um, know what they eat, uh, or how what they're eating is affecting their glucose, that can enable lifestyle adjustments that will stabilize blood sugar. Of course, the stabilized blood sugar will reduce glycation and the formation of advanced glycation end products and the subsequent inflammation that comes from it. Again, go view the hypoglycemia Metabolic Classroom for more details on that. But as I just mentioned, remember, for every glucose spike, there is an equal, if not greater, insulin spike, as a sort of metabolic version of Newton's principles. Um, so here, it's again, very important to appreciate the insulin impact that is going unmeasured, um, here with regards to the CGM.
And then there is just the real behavioral benefits that by having real-time glucose feedback, I, I sort of alluded to this earlier, um, that can drive behavioral changes, encouraging people to have better food choices when they see the impact of the food or their stress, whatever they're doing, how it's impacting their glucose levels. A study, um, noted that, uh, with, with real-time CGM feedback, um, people do make healthier choices. Um, one last comment on that, as I have seen it, so this is anecdotal in my observing, in my observing other people, um, CGM users become their own coach. That they don't need someone to tell them what to eat. They don't need someone kind of pointing the finger at them and directing them to one type of food or another. They end up doing that on their own. That, to me, is tremendously powerful, because the person is making it. It's, it's a motivation that's coming from, coming internally, which is far more impactful than you having a coach kind of nagging you to make a particular dietary change.
Okay, now, what, what can you do? If, if having heard all this, you're thinking, "Well, I'm interested." There are increasingly services, um, a group like Levels, for example, enables people to get the CGM and, and then very interesting software that comes with it. But also, there is, um, the, uh, increasing availability by getting them over the counter. Um, even though historically you'd need a prescription to do that, that that's ending soon, that you can get these, you know, monitors that last for 10 to 14 days that you're going to be able to buy just over the counter.
When you first start using the CGM, the data might feel a little overwhelming. And so, rather than trying to get into the nitty-gritty, just look at, look at a pattern over six or so hours. Let that be, or at least, um, where you're just really trying to focus on the pattern and looking at, um, which foods you ate. And even doing a little fun experimentation where you note in the app, and every CGM app has this ability, um, you note what you ate, and then just sit back and see what happens. Um, and then play around with it. What happened when you ate that same food and went on a walk? Very, uh, as a, now, personal anecdote, rather than sharing other people's, it was me looking at my CGM, um, that helped me identify that one of the reasons I was sleeping so poorly at one particular period of, of my life was that I was going to bed, uh, in a very hyperglycemic state. That while my evening indulgences, I had considered them to be only relevant to my potential of weight gain, um, I found that it was very disruptive to my sleep and it led me to explore the consequences of hypoglycemia at nighttime. And suffice it to say, it's not good. So, um, there's a tremendous value here in just getting these kinds of insight. Um, and pay attention to the time and range, so how often your glucose levels are in a healthy range, the variability, and then you'll be able to get the average glucose levels as well, all of which is helpful without getting, um, overwhelmed, without overwhelming you with data.
All right, so summing it up, we explored the science behind the CGMs, why they're such powerful tools for metabolic insights, not only for those with diabetes, of course, where the utility is obvious, but for anyone who's curious about how their body responds to various factors, most especially food. Even just trying a CGM temporarily can be very revealing in helping you identify some patterns of glucose responses that you might not have noticed otherwise. It's, uh, certainly a very small device, but the potential is enormous. And given its potential impact on how we approach health and nutrition, I hope this information has been helpful. I'll be interested, please share in any noting in the, in the show notes here, or make a comment and let me know how you have been using it and what you've learned. Thanks for tuning in. Until next time, more knowledge, better health.