What’s the deal with wearing continuous glucose monitors? These CGMs are little white dots that people stick in the back of their arm and it monitors the amount of blood glucose. Now these were made for people who’ve got diabetes. But it’s become a real trend to wear them and monitor your blood sugars, even though you don’t have diabetes.
In this episode, I’m going to explain why I don’t think it’s a good idea to manage your blood sugar levels in this way and have this much information about our health.
Hello, and welcome to episode 81 of the Inside Knowledge podcast for people with IBS, I’m Anna Mapson.
Can glucose monitors help with your gut health?
This podcast is all for people who’ve got digestive issues. So why am I talking about continuous glucose monitors? Well, often my clients are very interested in managing their blood sugars due to a lot of information on social media about managing blood sugar spikes.
There’s influencers like the glucose goddess. There’s also health programs like the Zoe program, which asks you to wear a blood glucose monitor for two weeks and these are really influencing my clients. So I wanted to explore it a little bit and be able to give a reference point for my take on it. I can explain a little bit about why continuous glucose monitors aren’t really necessary for people who don’t have diabetes.
How continuous glucose monitors support diabetes
Just to give you a reference point, I’m going to just explain a little bit about what is diabetes and then what is a problem level for your blood sugars so that we we know what we’re talking about. Whenever we eat food, our body breaks down the sugars, any carbohydrates, into glucose and that is our preferred form of energy for our cells. We get glucose in our blood from eating food and then the glucose circulates around our body.
In order to get the glucose into the cell we have insulin which helps to get it across the barrier into the cell. Type 1 diabetes is an autoimmune condition where your immune cells attack the pancreas and your body doesn’t make enough insulin or doesn’t make any insulin. Then you have a lot more blood glucose, you have high blood glucose.
Type 2 diabetes
Then you get type 2 diabetes as well, where either your body starts to become resistant to the insulin, or your body then stops producing enough insulin. So in that case, your blood glucose level is consistently and repeatedly high. And that can lead to damage to the nerves. If you think about when you spill a bit of jam in your kitchen surfaces, anything that touches that will become sticky and thick. And that can happen to your nerves, can give problems to your kidneys, you’re more at risk of cardiovascular issues like stroke and heart disease.
It just is really, really bad for your body to have ongoing very high blood glucose. That’s why people who have diabetes take medication. They take insulin to help them get rid of this problem. And doctors can measure how much you’ve got in your body and how much damage has been done by checking your blood sugars.
Tests for blood sugars – what get’s measured?
They will look at your fasting blood glucose. Before you’ve eaten first thing in the morning, they’re looking at how much glucose is in your blood. And then they also might do an HbA1c, which is looking at your blood glucose levels over a three month period, because that is how long your red blood cells last and that gets your kind of average blood glucose level.
And then they might also do a test where they will check your blood glucose after eating a high glucose meal.
The sort of things your doctor would look at is a fasting blood glucose level of seven millimole per litre or more.
If you’ve done a HbA1c tests, they’re looking at 6.5 or more and those would really indicate that you have got a problem with your blood sugars.
So those kind of metrics we should keep in mind as we’re just going through this next little bit about blood glucose monitoring.
What is normal for blood sugar rises?
It is normal for your blood sugars to rise after you’ve eaten a high sugary meal. If you’ve eaten a lot of carbohydrates, a lot of sugars, then it’s normal for your blood sugars to go up. Even into this level and then to come back down again. But what we’re looking for is that your blood sugars return to normal within two hours. That is a normal response to a normal meal, and not anything that we should be pathologising.
Obviously, eating a healthy diet that’s not full of loads of sugar, that you are getting a balance of nutrients, fats, proteins, fibre, all of these things really, really important still.
But it’s okay if your blood glucose level goes up, as long as it comes back down quickly. That is how your body responds to glucose, and that is what your body is meant to do.
Do we need to minimise blood sugar spikes?
There are some people online and there’s people like the ‘glucose goddess’ who keep telling people that their blood glucose level should be as small as possible. At the moment we don’t really have the evidence that says lower is better as long as your body is getting your blood glucose level back down again within that two hour period after eating. It’s okay, so it’s normal for you to get an increase in your blood sugars within the first 20 to 90 minutes after eating.
What is a glucose spike anyway?
And there’s a real difference between what they might describe as a blood glucose spike or a sugar spike.
I’ve seen in a number of social media posts that people are being told to lower their blood glucose even if it’s within a normal range. That this is something that we have to manage and I think this is where the problem is. We’re trying to micromanage a normal physiological process in our body that doesn’t need micromanaging.
And by the way, there isn’t a clear medical definition of what is meant by glucose spike, so this isn’t a medical term and we don’t really know what that means.
What is a continuous glucose monitor?
A continuous glucose monitor is a little device, you’ve probably seen them, people stick in the back of their arm and it measures the amount of sugar in your blood in the tissues in your arm.
And there’s a slight difference between measuring the blood from your veins that your doctor will do and the blood in the plasma, but it’s you know, a small difference and there’s definitely a timing difference to that as well.
But for the purposes of what we’re talking about here today, a blood glucose monitor effectively is just measuring how much glucose is in your blood all the time. And it takes it either at like five minute intervals, maybe one minute or maybe even ten minute intervals and updates you on a little app on your phone.
Up to date information for diabetes
For people who’ve got diabetes, this is incredible. Like it’s giving them the tools to be able to manage it without worrying too much about, glucose dips and going hypoglycemic.
Problem is that a lot of people who are using these now don’t have diabetes. They’re using them to optimize their health; to tweak it and to micromanage it, as I was saying. A problem level would be, your blood glucose level staying at over 7. 8 mmol per litre after 2 hours of a big glucose meal.
That means your body is not clearing it. It is keeping it really high for two hours. But it doesn’t mean that you should always avoid your blood glucose ever getting to that point. It just means it shouldn’t stay there.
Blood sugar monitoring in non-diabetics
It doesn’t mean that you can’t ever get a higher blood glucose reading. That is some of the problem when we’re looking at this information. Ordinarily we wouldn’t know, we wouldn’t see our blood glucose rising. You normally can’t feel it and so it’s giving you an additional level of data that we don’t often have.
If you are thinking about how to control your blood sugars then the kind of things that you might want to take note of is
- how big was your blood glucose spike, how high does it go after?
- is it after every meal that you eat, is it consistently rising above 7. 8 or like 10 millimole per litre?
But at the moment, for people who are not diabetic, we don’t really have good consistent data about what is good or bad.
Most research says that, yes, your body should come down again one to two hours after eating, going up is normal, but that spikes over about 11. 1 millimole per litre are typically considered quite excessive.
What’s a bad blood sugar spike in non-diabetics?
But we don’t actually know from non diabetic people, is this a problem? Like, how many of these is considered bad? What does it mean if you have one spike per day? What about one spike per week? Should you be really trying to bring that down? Or is it a problem? So we think that this level of data sometimes it’s helpful to know, but it actually can increase a lot of anxiety about food. And that is one of the things I want to come on to, is actually what are we looking for and what are we hoping to find with this information.
There are some things that influence our blood glucose response to food when we don’t have diabetes that people might not be aware of, and you can get quite caught up in looking at the data from your continuous glucose monitor as a non diabetic. Maybe getting confused about the information and getting extra worried about what might be happening.
Blood sugar responses change throughout the day
Firstly, your blood sugar responses are meant to change throughout the day. Most people have a better response to foods they eat earlier in the day. And as we go through the day, our blood sugar response becomes worse.
The same meal eaten at the same time might have a different blood glucose response in the same people. People eating the same meal at 8am, 8pm and midnight had different responses to the same meal. So this shows that meal timing has got an effect on your glucose metabolism.
Even if you’re eating the same food, at each meal. When you’re eating the food, might have a response. What you might find is if you’re tracking using a CGM, you might find that you think, ‘oh god, I’ve eaten this food and like sweet potatoes have really messed up my blood sugars, therefore I shouldn’t be having sweet potato.’ But actually, is it the time of day that you’ve eaten it?
Blood sugar responses change depending on what else you’ve eaten
Blood sugar response can be affected by other meals you’ve eaten earlier in the day. So, we can’t predict what your blood sugar response will be to a certain foods based on what you’ve eaten because the timing of it makes a difference.
We eat mixed meals – this affects blood glucose
Also, we rarely eat just one particular food on its own. Most meals are mixed foods which include protein, fats and fibers. And a meal itself is the thing that causes your blood glucose to change rather than just one particular food. Which is again, why it’s impossible to make predictions about what you can and can’t eat based on data just from the glucose monitor. It doesn’t really make sense.
Exercise changes blood sugar responses
The other thing that can definitely affect your results is exercise. However active you are, it will affect your response to food that you eat. Now overall, generally, exercise improves your insulin sensitivity, so that means you get more efficient at packing away the glucose, your blood sugar levels will drop or will not rise as high. But actually in intense exercise, in the short term, your blood glucose levels can go up.
So you might see your blood glucose levels going up when you’re exercising and think, Oh, like I’m doing the right thing. Why is it going up? But actually, It’s, part of your body’s way of releasing that energy, so you’re, you’re getting more glucose in your blood in order to fuel your activity. And then after the exercise, your blood glucose response would be lower for one to two days.
Research participants did 40 minutes of really intense exercise and their blood glucose response was lower for one to two days. This was people who had diabetes and people who didn’t. So, you may find that your response to certain foods was better the day after you did your crossFit training or you did a run. Then another day you might eat the same food but you haven’t exercised for a couple of days before and then your blood sugars go up a lot more after eating that same meal. It’s nothing to do with the food it’s to do with your exercise.
So that’s another reason why you cannot predict the foods that are going to be good for your blood glucose because it’s so many different things that impact it.
CGMs have been calibrated for diabetes
Another reason why CGMs aren’t great for people who don’t have diabetes is that because they’ve been calibrated and set up for people who do have diabetes, we’re not quite sure if they are accurate at reading the data, especially at the lower end of the scale. So if you’re mostly staying in range or going under, we don’t actually know whether it is 100 percent accurate.
And there are studies that show that there is a difference in the readings from a CGM to blood drawn from your veins. There’s actually a 13 percent difference in one study from 2022. And the researchers used different meal combinations and then tested the blood glucose with the CGM readings and then they took blood, um, draw from the veins and these was in healthy adults.
And the CGMs underestimated the amount of time that people were spending in a normal range of blood glucose. And then sometimes we also have data that show different CGMs show different results in the same people at the same time. So another study took 16 healthy people, and fitted them with two different CGMs to track their measurements over four weeks.
And they were in an inpatient study, so they were being monitored all the time. The two CGMs showed different measurements. And, in addition, there were Differences in the same person eating the same meal from one week to the next. And this just shows it would be so hard to make any judgements about how your body will respond to food.
Because they couldn’t replicate the same glucose response in the same person in the same meal. They had different responses. And actually, I wanted to just highlight what some of the researchers said at the end of this study. They said, Misclassifying meals or foods as good or bad in terms of their CGM response may affect overall eating behaviours with potentially deleterious consequences.
Which is what I think is one of the main problems. Is you would read that data and think, oh my god, like my blood sugar shot up when I ate that food. I shouldn’t have that again. But actually, unless you can replicate it every single time with eating the same food, you can’t draw that conclusion from this data.
So there’s just a whole range of things that show it’s not accurate and it’s not reproducible, which is one of the tests of good science, basically.
You should be able to reproduce the effects. What the main problem with this is, and I’ve seen this in my clients, is that it gives you a lot of stress. Anxiety and worry about what you’re eating because you can’t feel your blood sugars going up. But when you see this data of it spiraling out of control and shooting up into the red, then it feels very worrying.
Should you do personalised nutrition programmes including a CGM?
I’ve seen reports from personalised nutrition programmes like Zoe, saying ‘you’ve got poor blood sugar control in response to eating their standardised muffin’. But when I looked at the data, they had a perfectly normal glucose response to eating a food. It had gone up and then it had gone back down again.
But this client had so much worry about whether they were causing inflammation, and lasting damage with their eating pattern, which was already very healthy.
Your money could be better spent elsewhere
And what I worry about is this, money could be spent on other things. We are all free to spend our money on whatever we want, of course, but CTMs are quite expensive, and if you don’t really need it, maybe you could spend your money on a nice meal out with your family, going on a weekend away.
Like, there are all kinds of things you could be spending that money on.
Why is blood sugar monitoring so trendy now?
The next issue that I see is that if you’re just focusing on your blood glucose, blood glucose, blood glucose. You might be missing other issues with your health. Why are you not so concerned about your cholesterol levels, or your blood pressure, or your triglycerides?
If you’re only monitoring your blood glucose, and you’re trying to minimize every blood glucose rise, then you might be, changing your eating pattern to a way that’s actually not that healthy overall. So, for example, you might notice if you eat a higher fat meal, your blood sugar spike is lower.
So, therefore, you might choose higher fat meals from now on. And over time, this could have an effect on your weight, your blood lipid levels, or your nutrient intake. You might also start avoiding foods like fruit, because they spike your blood sugars as well, per the data.
It’s making choices for you based on inaccurate data but also data that is only one part of the picture your blood glucose profile is important especially if you’re in that pre diabetic range. However, it’s also important to manage your cholesterol level, to have good muscle mass. These things are also really important, but we don’t give it as much attention. When you are outsourcing your body sensing to a device, you are missing a way to connect with how you’re feeling.
Too much data about our health can be harmful
So I feel a bit the same about people who are tracking their sleep with a Fitbit or a smartwatch, because People can wake up and think, oh, I feel all right, but then they look at their watch and they’re like, oh, I actually had a terrible night’s sleep. And it brings you down. It makes you feel more tired.
It makes you feel like actually things aren’t going so well. So instead of thinking about how we’re feeling, how our brain is working, how our digestion is working, we’re relying on data from a device. And as I’ve said, it’s just one part of the picture. thinking about how we feel and how our body is operating is more effective than just looking at the data.
What I see in my clients is quite a lot of fear about food that, oh, I had oats and my blood sugars went up, so I need to avoid them. I can’t eat oats. And this, I think, is the wrong conclusion to jump to. from information such as this, because you’re basing your food choices on this device, which as I’ve tried to highlight, it can’t, CGMs aren’t good at reproducing the same results.
So the same person eating the same meal from one week to the next will have different blood sugar profiles. And if we can’t replicate the results, then we shouldn’t automatically rule foods in or out based on that data. And anyway, even if foods do spike your blood sugars, as long as they come down again, there’s no issue.
Even if they were giving you a bad response, or what we might consider a bad response, then it doesn’t necessarily mean there’s anything wrong with you and you don’t necessarily need to avoid those foods. The reason I think Maybe you’re drawn to programs like this, which is giving you information.
It’s giving you data is And I have the same kind of conversations with people who are keen to do a stool test is they want more information because they feel really bad. And I completely understand where it’s coming from for people to wish that they had more information, they had the answer. I do really empathize with this kind of drive to find the root cause of your problem.
It’s unlikely to be your blood sugars, unless your doctor has asked you to do a diabetes test, and you’re in that pre diabetic range. Then yeah, sure, there are things that need to be done to your diet and your lifestyle.
Don’t waste money on a continuous glucose monitor
The majority of people who are doing this program are not in that range, and are still looking for answers for why they don’t feel good.
And I think probably a more holistic, personalised approach is what will help. And I know these programmes are called personalised nutrition programmes, but they are using algorithms, and a small section of your biological data to make decisions about and giving you instructions for what to eat. So I think just be very careful about information that you’re taking from an algorithm. Just be conscious that it’s not necessarily giving you the whole picture.
So look out for that coming up next. But yes, we’ll leave it there for this week. Thank you very much for listening to this episode of the Inside Knowledge podcast. Better digestion for everyone.
