Circadian Rhythm 101
Wake, eat, sleep - your body thrives on patterns & here's what to do with them
You’ve probably heard of “Circadian Rhythms” at some point - the 24 hour cycles that govern your body and mind. Most people have heard of the way it can affect sleep. But sleep is just one small part of the circadian cycles that govern the functions of your hormonal health, mood, digestion, focus… and, yes sleep.
The presence of artificial light, regulated working hours, unlimited food options, and alarm clocks (yes, alarm clocks) have many of us living as if we’re separate from time.
Separate from time!? You might be thinking, How can I be separate from time with an alarm clock!?
Your body has a natural internal clock. A system that, not unlike a mechanized watch, has gears and springs to regulate the face - in your case, the face is how you’re able to show up in your life and the gears are made up of your hormones and habits.
If you’ve ever had jet lag you know that mis-matched feeling well. In my personal case, unmanaged jet lag results in nausea, insomnia, vision issues, headaches, and a resulting miserable mood. But how many people are living their daily lives with insomnia, digestive issues, and grumpy AF not realizing they’re living in odds with their natural rhythms?
Being at odds with those rhythms doesn’t only equal a bad night’s sleep. In the short term it can mess with the immune system, digestion speed and timing, and mental health. Long term it can increase risks for cancer and neurodegenerative diseases like Alzheimer’s and Dementia.
The Light in Your Eyes
While there are many regulators to circadian cycles, the primary one is deep in the brain’s limbic system as part of the hypothalamus. Signals from a bundle of nerves in the hypothalamus are sent to the Pineal Gland, even deeper in the brain and present in most animals. The pineal gland produces melatonin.
Many clients and students over the years were unaware: melatonin isn’t just a supplement! It’s a hormone your body naturally produces - unless there’s something up with the pineal gland.
One of the main switches to keep melatonin low: light into the eyes.
Light entering the eye stimulates the hypothalamus, signaling the pineal gland to keep it down! We’ve still got to be up! There are other forms of stimulation; but there impacts are negligible compared to light.
One of the most effective strategies for improving sleep, sleep timing, and reinforcing circadian rhythm is early morning light exposure. Exposure to sunlight upon waking for 30+ minutes - if sunlight is unavailable the brightest light possible.
What about blue light?
A few years ago blue light blocking glasses became all the rage.
Every influencer and biohacker had a rev-share deal with a glasses company and proselytized what time they put their blockers on.
The problem? It isn’t only blue light keeping us awake.
It’s also the brightness and intensity of light in the later half of the day.
You can wear the best blue-light blockers in the world; but if you’re starting at a phone 3” from your face 3 minutes before you try to sleep, you’re not going to sleep well.
Period.
Feel the Rhythm!
So what does a healthful circadian rhythm govern? Let’s start when you wake up. You get up without an alarm clock, rising gradually out of shallow sleep. This gradual waking relates to healthy cortisol production. Often labeled the “stress hormone”, cortisol is better titled an “alertness hormone”, and in a healthy circadian cycle you wake from it’s peaking.
You likely use the toilet, possibly having a bowel movement. If not then, it will happen on it’s own within the first 90 minutes of waking due to hormonal stimulation of the colon.
You get natural sunlight - perhaps through a walk. If not, bright artificial light within the first hour is advisable. You’ll likely get hungry within this first 90 minutes as well as digestion increases with activity and wakefulness.
Hormonally, within 90 minutes of waking you should be alert and have a sense of focus for the next 90 minutes. (These 90 minute cycles of alertness, or lack of, are called Ultradian Rhythm and relate to dopamine production.)
In the early afternoon you’ll have the best physical acuity, reaction times, cardiovascular efficiency, and strength outputs.
As the sun begins to set you’ll have your final meal of the day, beginning to reduce light and sound stimulation - anything that your nervous system would perceive as a threat. The stimulation of the fight or flight system would increase cortisol and keep you awake. The low light conditions allow the hypothalamus to nudge the pineal gland to start pumping up the melatonin.
Some point in the evening you’ll get sleepy and allow yourself to go to bed. At the start of your routine sleep window you’ll get deep phase sleep, allowing the brain to wash itself and many tissues throughout the body to be repaired. During sleep digestion and urine production are slowed (frequently waking to get up to pee is a sign of sleep apnea or other sleep dysfunction).
As the night progresses deep sleep lends itself over to REM sleep, during which most dreaming happens.
Then, rinse & repeat.
Living for the Weekend
For those with office-based jobs, studies of circadian cycles show many people trying to live on two clocks: the weekday alarm-clock-shock, and the weekend “sleeping in”. Much like jet-lag, it contributes to the feeling that Mondays are miserable.
For 2 days your body is pulled off it’s cycle - the jet lag equivalent of jumping from NYC to LA for the weekend and back. Most of us start those patterns in adolescence and persists until retirement, wearing away at the repair and restorative functions our bodies evolved for and acclimating to a “normal” until far after it can be restored.
Yet, we wonder why we struggle to sleep in our 40s, 50s, and beyond.
To worsen the physiological challenge - deep phase sleep is mostly at set times in the circadian cycle. Meaning, when we stay up later than usual, we’re essentially skipping deep sleep for a few days.
Theory into Practice
Let’s drive home the key takeaways to improve your own wellness practices:
Wake at a consistent time, even on the weekends
Get up, get moving, and get sunlight (or bright light in a pinch) within the first 30 minutes of waking, ideally for at least 30 minutes
Have meals during consistent times. Have the last meal a few hours before bed.
Cut caffeine mid day, ideally 6+ hours before sleep (there’s a caffeine article in the works with more details)
Dim bright light and trim screen time and brightness as you move into the evening (you might consider lowering volume of sound as well)
Keep consistent “screens off” and in bed times - approaching that time should also focus on calming the nervous system and quieting the mind
This draws heavily on the work of Dr Andrew Huberman. I’ll be keeping it simple for the non-technical audience; but if you want to nerd out hard here are a few things to check out:
https://hubermanlab.com/toolkit-for-sleep/
https://hubermanlab.com/sleep-toolkit-tools-for-optimizing-sleep-and-sleep-wake-timing/
https://www.nature.com/articles/497S10a