Cortisol Part I: Stop the anti-cortisol rhetoric

Morning moods and respecting "the stress hormone". First in a new series about cortisol and circadian rhythmicity.

Blaming cortisol for health problems is like blaming EMTs for accidents. It doesn't make sense. Cortisol is an endogenous (made by the body) hormone with many vital functions. Like vitamin D, another endogenous hormone, cortisol comes from cholesterol. In today's post, I will share a more welcoming and integrated view of cortisol. This is the first in a new series all about learning to appreciate the “stress hormone” cortisol.

Cortisol helps you wake up

Each day, we get up and activate our circadian systems with light and breakfast. That may be turning on lightbulbs in the house, or, better, stepping outside to greet the sun. Breakfast may be a nibble of something sweet and a gulp of caffeine, or, better, a full and savory meal. Either way, it turns on the circadian rhythm. How do you tend to feel in the morning?

Waking with a lot of mental energy in the morning can be evidence of a strong circadian rhythm. Waking and feeling sluggish can be evidence of the opposite.

One of the ways we could measure rhythmicity would be by looking at our daily cortisol rhythms. This is a test you can get from your doctor, but it is a hassle because you have to measure all throughout the day.

A single cortisol reading doesn't tell you much, because cortisol is circadian. It's level in the body depends on what time of day it is. At least, it should.

This graphic showing the central and peripheral circadian controls comes from a paper linking circadian rhythms, cortisol, and cardiovascular health outcomes.

One of cortisol's most important jobs is to keep the outer circadian clocks in time with the central one. To summarize, light triggers the brain, and the brain sends out cortisol to sync the body. In science-speak, the central circadian clock uses cortisol to sync the peripheral clocks. You may have heard of cortisol as the "stress hormone." It is also a wakefulness hormone, and so much more. Even without “stress,” cortisol would still have a full-time job in the body.

By looking at this graphic, you can see how light plays a big part in cortisol levels.

This is the first in a new series I'm writing about learning to appreciate cortisol. Here’s Part II:

Cortisol Part II: Optimal Rhythm