Providing independent clinical excellence since 2005
Posted on Thursday August 8, 2024 in Health Screening
Not long ago, “flattening the curve” was a euphemism used by politicians to talk about the COVID-19 pandemic. Since then, with the advent of numerous health apps, including Zoe, the term “flattening the curve” is increasingly recognised as referring to one’s blood glucose levels, where transient peaks in blood glucose, or ‘glucose spikes’ are considered to be harbingers of poor health, and thus a “flat glucose curve” is desirable for wellbeing and ones future health.
Continuous glucose monitors (CGMs) were invented for insulin-dependent diabetics to help prevent comas induced by low glucose, where an excess of insulin led to a dangerous lowering of blood glucose. Since 2018, the use of these monitors has exploded, with widespread use in the non-diabetic health-conscious. It is now realised that for every diabetic patient, there are probably thousands of people who have transient glucose highs or ‘spikes’ that quite possibly contribute to long-term health issues, including inflammatory diseases. Inflammation is considered to be one of the main causes of non-communicable diseases in people over the age of 50.
While low blood sugar may cause symptoms of dizziness and sweating, it rarely occurs except in diabetics taking insulin. Transient high blood glucose excursions are common and do not usually cause symptoms. Similar to high blood pressure, glucose highs may therefore occur unnoticed for many years. In theory, transient spikes in blood glucose can cause tissue damage by excessive glycosylation and, according to basic research studies, can also release free radicals responsible for oxidative stress. However, only sustained elevation of blood glucose, not the transient variety, adversely affect red cell glycosylation. Therefore in most people demonstrating glucose spikes their HbA1C, a long-term marker of glucose levels used by general practitioners to diagnose diabetes and pre-diabetes, will be within the normal, non diabetic range.
Fuelled by media publications supporting lifestyle and health apps which use continuous glucose monitors to attract customers, a spiking blood glucose has been widely viewed as potentially very harmful. However, what is the evidence for this?
Part of this story is linked to increased glucose variability (GV). Large epidemiological studies have shown that raised GV in both diabetics and non-diabetics appears to be linked to an increased risk of long-term cardiovascular disease[1-3]. However glucose monitors are relatively recent, and long-term population studies of using CGM to stratify risk are not yet reported. There are no published intervention trials reporting benefits of eliminating glucose spikes or excursions over set values (we use 7.8 mmol/L or 140 mg/dL as our ceiling of normality).
It is important to emphasise that until proper evidence emerges, all we can do is speculate about potentially harmful effects of glucose spikes and the possible benefits of intervening to prevent glucose spikes or “flattening the glucose curve.”
For cardiologists seeking the missing link between lifestyle and coronary heart disease, the glucose story comes at a good time, since nearly 50% of cardiovascular risk cannot be explained by traditional risk factors, including smoking, hypertension, raised LDL, raised Lp(a), and presence of diabetes. It is therefore certainly a very attractive idea that glucose excursions outside the healthy range may have a role to play, particularly because high glucose has been shown in diabetics to cause more inflammation and oxidative stress through the release of free radicals. As Jessie Inchauspé, author of Glucose Revolution, explains: “our mitochondria simply overheat and brown our tissues causing inflammation that could drive both coronary artery disease and dementia”.
Now that cardiologists have access to the Fat Attenuation Index (FAI), a marker of coronary inflammation, it has become clear that not all of our patients with high coronary inflammation linked to coronary artery disease have raised LDL or LP (a) as their main modifiable risk factor. We find a significant proportion also have glucose dysregulation. There is a wealth of evidence linking pre-diabetes, raised HbA1c, and full-blown type 2 diabetes to increasing cardiovascular risk. Lesser degrees of a pre diabetic metabolism could therefore have an important role in causing long-term atherosclerosis. We know atherosclerosis starts at a young age and grumbles on for many years undetected, so it would make perfect sense that something related to our modern diet and lifestyle, initially causing no symptoms, could be a root cause. Our eagerness for effective preventative medicine has therefore fuelled interest in measuring glucose metrics in any patient who has raised coronary inflammation and/or coronary artery disease.
Just as the discovery that high LDL Cholesterol in many people is largely related to inheriting one of the multiple PCSK9 gain of function mutations there is emerging evidence that we also inherit genes that code for how we metabolise carbohydrates [4]. Each of us handles carbohydrates differently, based on the genes we inherit and our lifestyle and food choices. Its plausible that, just like LDL Cholesterol and blood pressure, our metabolism, and how we each handle carbohydrate, forms part of each individual’s inherited risk.
With glucose interventions, we have to be careful. In the past, large trials were stopped prematurely due to an excess of deaths in patients being given drugs to lower glucose[5]. Unlike blood pressure and LDL cholesterol, where in general, it seems the lower the risk factor the better, the epidemiology of blood glucose metrics follow a U-shaped risk curve: both high and low HbA1c and glucose metrics are associated with higher mortality. It’s therefore easy to understand why medical teams are reserved about the claims of many health apps that glucose spikes should be treated aggressively. However, it should at least be recognised that this is an important emerging area, and by measuring the degree of the problem and matching it against the size of the risk or threat facing each patient, advice can be given to individual patients about tackling glucose variability / excursions outside the normal range. For our patients at risk, it seems logical to be promoting dietary and lifestyle changes already proven to be beneficial for the prevention of cardiovascular disease. In many cases, this means moving towards increasing physical activity, lower carbohydrate intake, higher fibre, and more balanced diet.
It seems relevant to mention at this stage the historic origins of the human food chain, beautifully set out in the book “Sapiens,” [7] which reminds us that the genetic code we have inherited from our past evolved over hundreds of thousands of years during which humans lived off the land. Until the very last moment in time, humans had a nomadic existence, and our diet consisted of berries, nuts, vegetables, scarce carbohydrates and sugars with just occasional intake of meat. Carbohydrates only arriving as a major food source since population expansion 2 – 3000 years ago. During this time, there has been limited evolutionary pressure to alter our metabolic pathways. Thus, in essence, modern Homo sapiens is poorly equipped to deal with the carbohydrate intake that the modern food industry and modern living serves us up.
Until adequate randomised controlled trials have been conducted of medical interventions that convincingly prove that altering glucose profiles to combat glucose spikes prevents modern diseases, we can only speculate and work on a best guess basis. All we can do is educate those at risk by sharing knowledge in this area. For those patients that embrace the idea and willing to speculate, we encourage conducting their own ‘N-of-1’ trial’ [9], to reduce glucose spikes by changing food and lifestyle [10-12]. With the help of a glucose monitor, it’s simple to experiment with different dietary ideas as set out in the best selling book ‘Glucose Revolution’. Anecdotal reports of significant weight loss, improved sleep and wellbeing also provide the hope that if our patients actually feel better, then they are more likely to maintain the changes. Some will also take an interest in food supplements that are ‘non medicinal’; such as curcumin, fennel, berberine and cinnamon mentioned in another blog, where there is some scientific evidence (but not large randomised controlled trials) showing significant glucose lowering activity.
In conclusion, the topic of blood glucose spikes is a fascinating and important area of study. While the evidence is still emerging, the potential implications for long-term health are significant. By taking a proactive approach to monitoring and managing blood glucose levels through diet and lifestyle changes, we can potentially mitigate the risks associated with these spikes. As research continues to evolve, it is crucial for both healthcare providers and patients to stay informed and adapt their strategies based on the latest evidence.
The medical understanding of a "heart attack" can sometimes diverge from the layperson's perception. Many people interpret a heart attack as any acute, potentially fatal cardiac event, regardless of its cause. This discrepancy necessitates a deeper exploration of heart attack causes unrelated to coronary artery disease, particularly for understanding familial risks and discussing preventative measures like statins.
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