Are you noticing that your blood glucose is highest in the morning when you wake up and you haven’t even had anything to eat yet? Don’t worry! This is a very common effect known as the dawn phenomenon. Let’s take a look at the science behind this phenomenon and explore strategies to help you reduce your fasting glucose.
What causes the dawn phenomenon?
The dawn phenomenon, sometimes referred to as the “dawn effect,” has earned its name from the recurrence of elevated blood glucose (a.k.a. sugar) around the hours of waking, roughly between 4-8 AM. Although the exact underlying causes of the dawn phenomenon are still unclear, it is known that hormones, including adrenaline, cortisol, glucagon, and growth hormone, play a large part. These hormones follow a circadian rhythm, or a daily cycle, and tend to be found in higher concentrations in the blood in the morning to help prepare us for the day ahead.
The hormones that promote glucose release into the blood include:
- Adrenaline: Known as the “fight or flight” hormone, adrenaline increases blood flow to the muscles and promotes the release of glucose into the blood.
- Cortisol: Known as the “stress hormone”, cortisol also plays a role in increasing blood glucose.
- Glucagon: Signals the liver to release glucose into the blood.
- Growth Hormone: Important for repair and regeneration and promotes the release of glucose into the blood.
Two key processes occur in the liver overnight that result in the release of glucose into the bloodstream and contribute to increased morning blood glucose:
1) Glycogenolysis, the breakdown and release of stored glucose (a.k.a. glycogen)
2) Gluconeogenesis, the creation of glucose from components of protein(i.e. certain amino acids) or fat (i.e. glycerol)
One more hormone that plays an important role is insulin. When blood glucose rises, insulin is released and helps move glucose out of the blood and into cells for energy use or storage.
Does the dawn phenomenon occur only in people with prediabetes and type 2 diabetes?
The physiological processes that underlie the dawn phenomenon occur in everyone regardless of whether they have diabetes or not. The difference lies with insulin and how our bodies react to it. Healthy individuals secrete enough insulin and are insulin sensitive enough to counteract a rise in morning blood glucose. However, someone with prediabetes or type 2 diabetes is insulin resistant and/or may not secrete enough insulin, which allows blood glucose to rise. This may be further compounded in the early morning hours because our body is more insulin resistant compared to the rest of the day (1) causing an elevated fasting glucose to remain elevated longer. Progression of prediabetes and type 2 diabetes is likely to result in a worsening of the dawn phenomenon as insulin function and sensitivity continue to diminish.