4 easy tips to optimize your circadian rhythm for better sleep, energy, and digestion
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Ever wonder why some days you wake up feeling refreshed while others feel like a struggle? Or why you get a second wind at night when you should be winding down?
That’s your circadian rhythm at play — your body’s internal clock that regulates everything from sleep and energy to digestion, metabolism, and hormone balance.
This 24-hour cycle is orchestrated by a tiny region in the brain called the suprachiasmatic nucleus (SCN).
The SCN acts as the body's master clock, telling the body when to perform which biological process and synchronizing countless biological functions, including sleep-wake cycles, hormone release, digestion, and body temperature regulation.
And the single biggest factor that keeps this clock in sync? Light.
Your circadian rhythm isn’t set by the numbers on a clock but by the natural light exposure you receive. Yet, most of us aren’t getting enough natural light during the day, while artificial light at night throws everything off.
The result? Poor sleep, sluggish digestion, unstable blood sugar, and feeling exhausted at the wrong times.
Why Light Matters More Than You Think
Light is the most powerful signal for regulating your circadian rhythm. When light enters your eyes, it sends direct signals to the SCN, telling your body what time of day it is and when biological processes should be happening.
This includes turning on digestion by stimulating stomach acid and pancreatic enzyme production, kickstarting hormone secretion like cortisol to promote wakefulness, and regulating neurotransmitters that impact mood and focus. It also influences metabolic functions such as insulin sensitivity, ensuring your body efficiently utilizes energy throughout the day.
If you love digging into the science, this fascinating paper explores how your circadian rhythm regulates digestion — from gut motility and nutrient absorption to its role in conditions like GERD and colorectal cancer.
In a world before artificial lighting, this system worked seamlessly. But modern life has completely disrupted our relationship with natural light, leading to widespread issues with energy, metabolism, and sleep.
Here’s How It Works
Morning Light: The "On" Switch
Getting bright, unfiltered sunlight in the morning signals to your brain that it’s time to wake up and be alert.
This triggers (just to name a few):
A cortisol rise (your natural wake-up hormone) to increase energy
Regulation of blood sugar and metabolism for the day ahead
The timer for melatonin production later that night to support deep sleep
But here’s the catch — unfiltered sunlight means getting outside. Light exposure indoors is significantly weaker than outdoor sunlight, even on a cloudy day. Glass filters out key wavelengths and reduces intensity, making it much less effective for setting your circadian rhythm.
For reference, here’s how the light intensity compares:
Sunlight through a window: ~500-3,000 lux (varies based on window type and weather)
Cloudy outdoor day: ~5,000-10,000 lux (still powerful!)
Sunny day: 50,000+ lux (instant wake-up mode)
Even on a gloomy day, outdoor light is up to 20x stronger than indoor light — and your brain can tell the difference.
Evening Light: The "Off" Switch
Just as morning light tells your body to wake up, darkness signals that it’s time to wind down by initiating the release of melatonin, the hormone responsible for making you feel sleepy. As light exposure diminishes, the SCN communicates with the pineal gland to ramp up melatonin production, reduce cortisol levels, and prepare the body for rest.
The problem? Most of us are bombarded with artificial light at night, which:
Suppresses melatonin, making it harder to fall asleep
Confuses your brain into thinking it’s still daytime
Dysregulates energy levels, leaving you tired during the day but wired at night
Over time, circadian rhythm disruption doesn’t just affect sleep — it throws off nearly every system in your body. Since your internal clock regulates digestion, metabolism, and hormone production, inconsistent or conflicting light exposure can contribute to blood sugar instability, sluggish digestion, fatigue, brain fog, and even long-term health issues like metabolic disorders and cognitive decline.
The good news? Small adjustments to your light environment can help recalibrate your internal clock and restore balance.
How to Work With Your Circadian Rhythm
The key to optimizing your circadian rhythm is aligning your light exposure with nature’s cycles:
Get morning sunlight ASAP – Step outside for 2-10 minutes within 30 minutes of waking (even on a cloudy day). Your brain needs full-spectrum light to properly set your internal clock.
Dim lights after sunset – Lower light levels in the evening to mimic natural dusk and avoid sending mixed signals to your brain.
Reduce screen time at night – Blue light from screens suppresses melatonin. If you must use screens, consider blue-light-blocking glasses or night mode settings.
Aim for complete darkness while sleeping – Even small amounts of artificial light at night can disrupt melatonin and sleep quality. Use blackout curtains and minimize glowing electronics.
A Small Change With Big Impact
Your circadian rhythm orchestrates everything from energy levels, to sleep, digestion, metabolic health, hormone health, and mental well-being.
Start with these simple shifts and see what changes for you. A few minutes of morning light and dimming screens at night can make a huge difference in how you feel. Try it for a week, and let me know what you notice!
This information is for educational and informational purposes only and solely as a self-help tool for your own use. I am not providing medical, psychological, or nutrition therapy advice. You should not use this information to diagnose or treat any health problems or illnesses without consulting your own medical practitioner. Always seek the advice of your own medical practitioner and/or mental health provider about your specific health situation. For my full Disclaimer, please visit www.alisonkeiper.com/disclaimer.