How Blood Sugar Levels Impact Your Mood
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Did you ever notice how you can get irritable or “hangry” when you are hungry? Do you feel jittery and anxious after a late-night candy binge? You can thank your blood sugar and brain for these mood changes. The brain is the most energy-demanding organ in the body. It is composed of a network of nerve cells (neurons) that are constantly working. Just as our muscles need energy to exercise, our brain also relies on a constant supply of fuel in order to sustain a high level of function. Since the primary source of fuel for the brain is glucose, changes in blood sugar concentrations significantly impact cognitive performance and mood. This need is especially evident in high-stress environments or work situations where there is high cognitive demand.
Glucose and the Brain
The brain’s primary fuel source is glucose through the generation of adenosine triphosphate (ATP) to power cognitive function. While the brain can use ketones as an alternative fuel under specific metabolic conditions, glucose remains its preferred source. However, unlike muscles and the liver, the brain cannot store glucose. This means that when blood glucose levels drop, the brain lacks immediate access to fuel, which can be problematic for individuals who are not metabolically flexible. They rely heavily on exogenous glucose (from food) to sustain physical activity may experience difficulty maintaining stable energy levels for brain function. For these individuals, when the level of circulating blood glucose falls, the rate of cerebral glucose metabolism will decline as well. This can result in changes in mood as well as cognitive performance.
How Does Blood Sugar Change Throughout the Day?
Your morning workout, an afternoon snack, stress, sleep patterns, hydration status, and certain medications can all impact blood glucose levels. Blood sugar naturally rises after meals, with carbohydrate-heavy meals causing larger spikes than meals where carbohydrates are paired with protein.
Exercise, particularly high-intensity activity (>60% VO2max), utilizes glucose for energy, effectively reducing circulating blood sugar.
Stress also plays a significant role in glucose fluctuations, as the release of cortisol and epinephrine can elevate blood sugar.
Sleep is an often overlooked driver of glucose dysregulation. When we limit our sleep our body doesn’t have the time it needs to go through a proper “reboot” overnight and it goes into emergency mode the next day. This means our blood sugar isn’t managed as efficiently as usual the next day.
Medications, including steroids and diuretics, may also contribute to blood sugar variability.
What Happens When Blood Sugar Drops?
When blood glucose levels fall, the body responds by releasing epinephrine (adrenaline), which signals the liver to produce more glucose. However, adrenaline also increases heart rate, causes sweaty palms, and contributes to feelings of nervousness or irritability. If blood sugar does not return to a normal range, the body releases cortisol, a stress hormone that further impacts mood and cravings. The combination of adrenaline and cortisol can result in heightened anxiety, frustration, and an increased urge to consume sugary foods.
How Does low Blood Sugar Impact our Mood?
Hypoglycemia (blood sugar less than approximately 70 mg/dL) can increase feelings of anxiety and confusion. This can make it challenging to stay on task and focus. Low blood glucose leads to a loss of mental focus and feelings of weakness, like the mental fatigue we experience the hour before our lunch break. Signs of low blood glucose are dizziness, shakiness, headache, and irritability. This can be especially challenging for individuals engaged in cognitively demanding tasks or prolonged periods without food. Clearly, none of these symptoms are desirable but many of us frequently experience them (remember the last time you were “hangry”?).
How Low is Too Low?
Blood sugar levels vary from person to person, but most individuals experience symptoms of hypoglycemia when levels drop below 70 mg/dL. In non-diabetics, low blood sugar can be triggered by certain medications, excessive alcohol consumption, or high-sugar meals that lead to a rapid post-meal crash. In diabetics, factors such as excess insulin, skipped meals, and increased physical activity can contribute to hypoglycemia. The key to mood stabilization lies in minimizing extreme fluctuations in blood sugar.
How Does High Blood Sugar Impact our Mood?
Hyperglycemia (high blood sugar) for non-diabetic individuals occurs when blood glucose levels rise to more than 180 mg/dL one to two hours after a meal or 125 mg/dL when fasted. This is a very large spike for a non-diabetic and can be caused by a high sugar intake, some medications (steroids and diuretics), major illness, injury, or chronic diseases. In the short term, hyperglycemia can induce feelings of fatigue, anger, or sadness. A study that examined the effects of acute hyperglycemia on cognitive function in individuals with type 2 diabetes found that cognitive function was impaired and mood state deteriorated during acute hyperglycemia.
Chronically high blood sugar is problematic as well. Persistently high blood sugar (due to poorly managed diabetes) may also worsen depressive feelings or increase anger.
When hyperglycemia occurs, the sudden rise in blood sugar triggers the body’s release of insulin. Insulin release is a healthy response that initiates rapid glucose uptake by tissues, which either stores the glucose as glycogen or uses it for energy production. An overproduction of insulin, however, causes a rapid decrease in blood sugar below normal levels (reactive hypoglycemia). This reactive hypoglycemia can impact mood by making it difficult for us to concentrate, anxious, and irritated.
How to Maintain Stable Blood Sugar
Several lifestyle factors influence blood sugar levels, including diet, exercise, stress management, sleep, and hormonal balance. Luckily, we do not have to be perfect in each of these categories in order to have blood sugar levels that stay within a healthy range. Small, strategic changes can make a significant impact. Since stress is arguably the factor that is least within our control (hello last-minute school projects for kids or a boss suddenly piling on the work), adjusting our diet is one of the most effective ways to stabilize blood sugar and improve mood. Focusing on food is usually a good place to start since it requires less time commitment, is easily modified, and has the potential to cause the greatest spikes in blood sugar and, thus, harm our health. Here are a few strategies to help get you started with blood sugar stability.
Simple Strategies for Blood Sugar Stability:
- Prioritize Protein-Rich Foods – Swapping simple carbohydrates (such as processed foods and sugary snacks) for protein-rich meals helps maintain steady blood sugar levels, reduces cravings, and prevents energy crashes. Protein promotes satiety and prevents sharp spikes and dips in glucose that can lead to irritability and fatigue.
- Let GOOD IDEA Help – If you anticipate consuming a carbohydrate-heavy meal, drink 1/3 of a can of GOOD IDEA before eating and finishing it with your meal to help stabilize post-meal blood sugar levels. Clinical studies have shown that this approach reduces post-meal glucose spikes by an average of 25%. This can help to mitigate mood fluctuations associated with dramatic glucose swings.
- Optimize Meal Order – This is a simple tip you can implement immediately. The sequence in which you eat your food influences blood sugar responses. Studies suggest that consuming vegetables first (such as a starter salad), followed by protein and fat, and finishing with starches and sweets can significantly reduce blood sugar spikes when compared to when the exact same meal was consumed but with the starches/sweets eaten first. This simple adjustment can enhance metabolic health and prevent mood swings linked to blood sugar fluctuations.
By implementing these small but effective changes—prioritizing protein, incorporating GOOD IDEA with meals, and adjusting meal order—you can minimize energy crashes, stabilize mood, and enhance overall metabolic health. And as an added benefit, better blood sugar regulation supports long-term health, providing an extra boost to your overall well-being and mental clarity.
Author: Dr. Colleen Gulick, Ph.D. (ExPhys), MS (ExPhys), BS (BioE), EIT (ME), CSCS