Continuous Glucose Monitors - What’s the big deal?
If you frequent social media, you probably are inundated with more and more ads in your feed about the benefits of continuous glucose monitors (CGMs). It seems like we are approaching a tipping point with these devices. When they first came out, they were prescribed to people with diabetes who take insulin. CGMs were designed to improve diabetes management and avoid the need for multiple daily fingersticks. Next, elite athletes started to use them to maximize performance. Now, they are being marketed as a potential benefit to almost everyone as a tool to support metabolic health. So, it seemed worth taking a bit of a deep dive into the world of CGMs.
In this article, I provide an overview of CGMs, what they are, why they're used, why one might consider using one, and some potential downsides. In a future article, I will share some personal observations from wearing a CGM and answer additional questions that I receive from you.
What is a CGM, and What Does It Do?
Continuous Glucose Monitors, or CGMs, are compact devices that measure glucose levels in the fluid under your skin, providing a reliable indicator of blood glucose levels. Originally designed to assist diabetics in managing their blood sugar, CGMs offer real-time glucose monitoring without painful finger sticks. These small, virtually painless devices resemble a raised button and are inserted on the upper arm, where they are worn for 14 days. CGMs wirelessly transmit updated glucose measurements every minute. These measurements are displayed in user-friendly graphs and charts accessible through a smartphone app. These easy-to-understand visuals make it easy to quickly discern patterns in blood sugar levels by time of day. The built-in log feature also allows you to cross reference meal timing, type of intake, sleep, and exercise and how this impacts blood sugar levels.
How Do Blood Sugar Levels Relate to Health?
Our body's metabolism is a complex process that converts the food we eat into cellular energy to fuel all bodily functions. All foods, whether composed of proteins, fats, or carbohydrates, can be transformed into energy. However, it's carbohydrates, particularly the simple sugars glucose and fructose, that play a key role in this process.
Chronic elevations in blood sugar levels lead to two processes that can accelerate aging and increase wear and tear on the body's structures.
The first process is called glycation. In glycation, the outside of our cells become coated with sugar molecules - you can think of it as candy-coating the outside layer of our cells. (This is not a good thing). When your doctor measures your hemoglobin A1c level to screen you for diabetes or monitor your diabetes control, they measure the level of glycation (candy-coating) on the outside of your red blood cells to indicate your average blood sugar over the last three months.
The second process is oxidative stress. Remember that any burning of fuel involves waste products. Think about your car, if it runs on gasoline, the exhaust that comes out of the tailpipe. Our body is no different. In addition, certain types of cellular fuel sources create more ‘exhaust’ than others. For instance, the sugars fructose and glucose create by-products that can damage cell structures. This process is called oxidative stress.
It is well recognized that chronically elevated blood sugars, like those seen in diabetes, are associated with elevated risks for various chronic health conditions like heart and kidney disease, eye disease, and nerve damage. These occur largely due to oxidative stress and glycation processes and the damage that results, especially to blood vessels.
You can think of oxidative stress reactions like the rust that forms on metal. The cumulative effects of these oxidative stress reactions are cell and tissue damage and accelerated aging. Elevations in blood sugar that cause higher circulating levels of blood glucose drive these processes.
Since biology exists along a continuum, it stands to reason that elevated blood sugar levels, even in non-diabetic individuals, may cause long-term harm. There is evidence that individuals with post-meal glucose spikes (even in the non-diabetic range) are at increased risk for cardiovascular disease.
It is also clear that in the short term, glucose spikes are associated with many symptoms that impair quality of life and may contribute to poor long-term health outcomes (e.g., food cravings, sleep disruption, and mood disturbances).
Importantly, elevated glucose levels are often a marker of insulin resistance. Insulin is the hormone that allows blood sugar to enter our cells to be used for energy. In insulin resistance, our body needs to make more and more insulin to maintain a stable blood sugar level. Elevated insulin levels lead to several other effects, including elevated blood pressure, fatty liver disease, and cognitive issues.
Why Might You Consider Using a CGM?
A CGM can be a valuable tool if you experience food cravings or energy dips at certain times of the day. It may help you discern if the underlying cause is related to blood sugar balance. In addition, if you have a family history of diabetes or prediabetes, but normal screening tests, a CGM may provide additional insights into how your body manages glucose, potentially allowing you to identify and reduce risk. Finally, blood sugar fluctuations can trigger hot flashes, impact sleep quality, and contribute to mood issues, so CGM could be a tool in assessing and managing these conditions.
What Are the Downsides?
While CGMs offer significant benefits, they have some drawbacks to consider. First, they require a prescription. Costs, while decreasing, can still range from $30 to $80 for a 14-day CGM. Some companies are finding workarounds and offer CGMs directly to consumers. They usually have staff healthcare providers who write the prescriptions for additional costs. There are ecological concerns as well. While CGMs represent a more ecologically sound choice for diabetes care, CGMs are not recyclable or safe for regular municipal disposal, posing environmental concerns as their usage grows among non-diabetics. Finally, for individuals with a history of disordered eating or tracking compulsions, CGMs may not be suitable.
What Are the Benefits?
CGMs provide a useful tool for self-assessment, especially if you are motivated by objective data and have some of the health concerns I noted. Using them, you can correlate what you experience in your body during blood sugar spikes in real time and learn these signals so that you can be aware of them. These insights could inform and motivate day-to-day choices even when not wearing a CGM.
CGM studies have shown that the blood sugar spikes associated with foods are highly individualized. While there are general trends/rules, there is also a lot of variability. What spikes blood glucose in one person may not affect another. It also allows one to see the real-time impact of sleep quality, stress, and movement on blood sugar levels.
In conclusion, CGMs are a tool that can offer insights into your metabolic health. While they have their drawbacks, there are potential benefits. Stay tuned for a future article where I'll share my experiences and findings while wearing a CGM.
And let me know what questions you want me to answer in a future article.
To your health,
Dr. Nicole
