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Is it possible to feel more mentally sharp and clear-headed by tracking and controlling our glucose? Research suggests yes.
How often do we blame ourselves for not being able to focus? How often do we associate an inability to focus on the task at hand as a personal failure? How many extra cups of coffee do we drink every week to try to steamroll past the mental fog and accomplish our goals?
Many individuals may be living life at a cognitive disadvantage, which may stem from a lack of metabolic awareness, a variable that many of us aren’t focusing on. If we aren’t aware of how our body and brain respond to what we eat and how glucose affects mental clarity, we’ll be shooting blame darts in the dark, unnecessarily adding more stress into the equation.
Glucose and Mental Clarity
Mental clarity refers to the ability to think clearly and maintain mental focus and attention. Interestingly, these traits all have more to do with metabolic health than we might think. The sensations of fatigue, reduced alertness, and an overall feeling of your energy being sapped have all been linked to volatile swings (both spikes and dips) in our glucose levels, as well as elevated fasting glucose levels.
If your glucose levels are too low, you may feel shaky, hungry, anxious, dizzy, and even nauseous. If your glucose levels are too high, you can feel fatigued, experience weight gain, mood issues, and have trouble remembering things.
Ultimately, we want to keep our glucose fairly stable and in a healthy range. By doing this, we “train” the body to be efficient at using glucose and fat for stable energy and mental clarity, a process called metabolic flexibility. If glucose levels are frequently high because of our dietary and lifestyle decisions, our body doesn’t get the opportunity to “learn” how to harness fat for energy efficiently. This puts us in a position where we may feel lethargic and mentally foggy if we don’t have constant access to glucose.
We may be most familiar with these sensations in the “post-meal energy slump,” a plummeting of focus and energy levels that comes after eating a massive carby meal.
What Does the Research Say?
Research has established that type 1 and type 2 diabetes, diseases associated with impaired glucose regulation, are tightly linked to cognitive impairments.
The question becomes, as people progress from normal metabolic function, to impaired glucose tolerance and prediabetes, to diabetes, does the cognitive dysfunction creep up as well?
We know that even healthy individuals whose fasting and post-meal glucose levels fall into the non-diabetic range can still display patterns of less optimal glucose control, such as big swings in glucose, rising fasting glucose levels, and sustained glucose elevations after meals.
In recent history, we’ve understood some of these more nuanced patterns of glucose responses to foods thanks to the emergence of continuous glucose monitors. Studying whether these dynamic glucose response patterns are clinical indicators of early dysfunction is an active research area.
We know from the research that it doesn’t meet the absolute clinical criteria for diabetes to show early signs of metabolic dysfunction and associated cognitive impairment.
A 2010 study noted that individuals with evidence of insulin resistance, but not yet diabetes, performed worse on cognitive function tests that included assessments such as declarative memory and executive functions such as utilizing higher-level cognitive skills to coordinate behavior and resources to reach a goal.
Additionally, a 2011 study of young non-diabetic participants showed that people who had the worst glucose responses to a glucose-loaded drink were more likely to do worse on memory tests. In the study, 122 young adults were given the glucose drink and then categorized into three groups based on their response: “better glucose regulators,” “average glucose regulators,” and “worse glucose regulators.”
The “worse glucose regulators” category, defined by those who had the slowest rate of glucose recovery after a glucose peak (i.e., a more sustained glucose elevation), did the poorest on a variety of verbal memory tests, which included assessments like word list recall, paragraph recall, and word order recall.
The study concluded that decreases in cognition can be seen in young, nondiabetic adults, even before meeting any clinical criteria for metabolic dysfunction.
One interesting facet of the research is that the “worse glucose regulators” also had similar baseline glucose levels as the other two groups. Still, their 30-minute and 60-minute glucose levels were substantially higher than the other two groups, demonstrating they had higher post-drink glucose peaks and were slower to get their glucose levels back down after ingestion. These participants also had higher insulin levels after the glucose drink consumption, which suggested they exhibited the early stages of insulin resistance.
Taken together, the data from this study suggests that we would be wise to be tracking more than just a yearly fasting glucose level as a true measure of metabolic health.
As we can see, more detailed, dynamic measures of glucose responses to food may hold hints to early underlying problems that we can intervene on. What’s more, it suggests that tweaking our diet and lifestyle to improve our glucose responses and metabolic fitness could sharpen our mental clarity.
A Note On Fasting
Fasting has been called “exercise for your brain.” It has been credited with improving the “plasticity” of the brain’s synapses, increasing the levels of brain derived neurotrophic factor (BDNF), and impacting how quickly brain cells respond to information. Certain fasting regimens like “16-8” (16 hours fasting and 8 hours eating in a 24 hour period) are also credited with stabilizing glucose levels. With continuous glucose monitoring, individuals can track the progress of their fasting and see how glucose levels respond, and connect this with whether there is a change in mental clarity.
Mechanisms: How Might Glucose Regulation Affect Cognition
There are multiple potential mechanisms for how glucose regulation might affect cognition.
It is possible that elevated glucose levels can directly negatively impact the part of the brain associated with memory: the hippocampus. What’s more, research has shown hippocampal shrinkage in non-diabetic older people with impaired glucose tolerance.
Additionally, glucose dysregulation may lead to problems with insulin sensitivity, which can affect cognition. Studies have shown that memory processing leads to the increased genetic expression of insulin receptors in the brain’s memory centers (hippocampus), presumably because more activity requires an increased intake of glucose for energy. Research has shown that insulin transport into the brain is reduced in chronically high insulin levels (which is seen with poor glucose regulation states). While not fully established yet, there is evidence that the association between poor glucose regulation and decreased cognition may be related to decreased insulin in the brain or dysfunction of the brain’s insulin receptors.
Data suggests an opportunity to improve our cognitive performance by keeping our metabolic health and insulin sensitivity as sharp as possible. Gaining insight from CGM into how glucose patterns are associated with feelings of mental clarity or mental fog can help build intuition and awareness that serve as the foundation for optimizing our choices.