Blood Glucose and Brain Function: It’s a Two Way Street

Glucose is an essential fuel source for our brain. Our brain requires 25-35% of our blood glucose throughout the day. It is important to maintain a steady state of glucose in our blood. Insulin and glucose responses have significant impacts on amino acid/protein transport through the blood brain barrier. Fluctuations in insulin and glucose levels can impair our brain function, increase neuroinflammation, increase in oxidative stress and promote Lewy body and beta amyloid plaque build up. These are contributing factors to neurodegenerative disorders such as dementia and Alzheimer’s disease. 

Blood Glucose and Insulin: The Dynamic Duo

How do we alter blood glucose levels? Our blood glucose levels depend very highly on WHAT we eat, WHEN we eat, HOW frequently we eat and HOW MUCH we eat.

If we eat three large meals a day that are filled with processed foods, high carbohydrate load and with very little protein and fiber then our blood sugar will spike after we eat those meals. This is caused by insulin. When we eat, our pancreas releases insulin into our bloodstream. Insulin is a glucose molecule’s gatekeeper into our cells. Without insulin we could not intake glucose into our cells efficiently.

Ideally, we should eat three smaller meals filled with whole foods that have substantial protein, fat, fiber and carbohydrates and in between each meal our snacks are filled with unprocessed high protein and high fat. To keep it simple, everytime we eat, especially with a higher carbohydrate snack/meal, insulin spikes in response to help bring the glucose from our meal into our cells as fuel. 

How do we become insulin sensitive? Insulin is a hormone, and like all hormones our bodies get used to hormones and become less sensitive to our production of them.

When we are constantly spiking our insulin with big meals, higher carbohydrate diets, lack of physical activity, alcohol consumption, pleasure eating, etc., our body produces copious amounts of insulin in response. Over time, our body becomes less sensitive to our insulin, which results in more glucose remaining in the blood and not enough being taken into our cells. This is problematic.

Also, with constant insulin spikes throughout the day, this can cause our glucose levels to go up and down constantly throughout the day. This is problematic as well, because our brain and cells do not get adequate amounts of fuel through the day. Ever heard of being HANGRY? This is it! To be hangry is when your blood sugar drops between meals and your cells and brain are not getting an adequate amount of fuel.

Brain → Blood Glucose Connection

Our brain is constantly monitoring our blood glucose levels. This is done through our hypothalamus, which is a collection of cell bodies that sits just above our brainstem. If there is a decrease or increase in blood glucose levels, our hypothalamus will communicate with other areas of the brain and/or the metabolic system (adrenal glands, pancreas, liver, etc.) to help adjust the blood glucose levels.

If our blood sugar is dropping through the day the hypothalamus signals to our satiety centers, temporal lobe and midbrain. Our hypothalamus will signal to our satiety centers to make us hungry, so we’ll eat again. It will signal to release cortisol releasing hormone to the pituitary gland. This will cause our adrenal glands to release cortisol into our blood system – this is our stress response hormone. Cortisol will affect our temporal lobe, specifically our hippocampus which has a lot of cortisol receptors located in it. Do you ever feel brain fog or do you have a hard time remembering things when you’re hungry? This is why! Our temporal lobe houses our hippocampus which is where our memory is stored in the brain. 

In addition to all of this, our hypothalamus will communicate with our midbrain. Which is located in the brainstem. It will excite our midbrain which will create an additional sympathetic response. This causes catecholamines (adrenaline) to leak into our bloodstream, increase heart rate, blood pressure to rise and sweating. Do you ever get shaky, anxious, lightheaded or nauseous when you are between meals or skip a meal? This is why!

When we go for long periods without eating or we allow our blood glucose levels to drop throughout the day our brain causes all of this to happen so it can regulate these levels and cause us to eat. These are naturally occurring adaptations that our brain does but we do not want this happening throughout the day. We do not want to be periodically dipping into our adrenaline stores or causing excess cortisol release everyday. This can lead to anxiety, panic attacks, sleep disturbances, memory disturbances/decline, chronic fatigue, brain fog, headaches, dizziness, etc. These are some of the many symptoms that can be experienced with alterations in our blood glucose levels.

How do we prevent this?

This response is a brain to body connection, but it is influenced by our control over our blood glucose which is controlled by our diet and lifestyle. Meaning that it is a brain to body connection, but it is also a body to brain connection as well.

We can help stabilize our blood glucose levels by breaking our fast in the morning with a high protein food, this will help level off our blood glucose levels through the day. Eat smaller non-processed meals three times per day with high protein/fat snacks between the meals, and eat something higher in fat 30 minutes to 1 hour before bedtime. We want our diet to consist of non-processed food with high protein and high fiber. This can consist of eggs, lean meats, vegetables, raw nuts/seeds, etc. In addition to this, adequate sleep (7 to 8 hours), reduction in caffeine intake, regular physical activity, and increased water intake will help to stabilize our blood glucose over the day.

At CFNC, we utilize various objective tools to evaluate a patient’s blood glucose regulation if it is indicated. This consists of things such as lab work, cortisol testing, etc. Regulation of energy levels and blood glucose is very important for brain function, neurological rehabilitation and healing. We feel it is of the utmost importance to evaluate this with our patients and target this during our treatment if needed.