Reliable Sleep, Again
The Circadian Rhythm Is A Weapon Against All Disease
Your circadian rhythm could be the most deeply important area for recovering and protecting your health — especially in chronic illness and aging.
Your health is limited or improved — magnificently — by the quality of the circadian rhythm.
Explore this article:
1 — Melatonin, The Hormone Of Sleep
2 — The Melatonin Cycle
3 — Light Cycles Control Melatonin
4 — Darkness Raises Melatonin
5 — Modern Melatonin Cycles Are Broken
6 — The Brain’s “Clock”
7 — The SCN Knows Time Of Day
8 — Bright Light Lowers Melatonin
9 — Brightness & Color
10 — Good Light & Bad Light
11 — The Day/Night Light Cycle
12 — Color Temperature
13 — Sunlight’s Changing Color Temperature
14 — Meal Timing Affects Circadian Rhythm
15 — Other Factors
Explore the Sleep section
“You get a show or a movie you’re really dying to watch and you end up staying up late at night, so we actually compete with sleep,” Hastings said, adding triumphantly, “And we’re winning!” (Nov 3, 2017)
Interestingly, China is the most sleep-medicated country in the world.
79% Of Americans Are Sleep Deprived
The average American only sleeps 6.8 hours per night.
Melatonin: The Hormone Of Sleep
The human body can’t sleep without melatonin rising at night.
When Melatonin Rises, The Body Feels Sleepy
Melatonin is the primary component that tells the body it’s time for sleep. When melatonin rises, it may not be possible to stay awake.
This can observed when children fall asleep — anytime, anywhere. This is robust melatonin in action.
By contrast, when people struggle to fall asleep and stay asleep, this powerful release of melatonin is not occurring optimally.
What Causes Melatonin To Rise?
Darkness is the main component that causes melatonin to rise.
A Healthy Melatonin Cycle
High By Night, Low By Day
Melatonin must rise high at night to facilitate sleep.
For melatonin to rise at night, melatonin must be low all day.
Melatonin — Rises After Dark
Melatonin rises at nighttime, just before bed — to make you fall asleep (and want to fall asleep).
Melatonin — Drops In The Morning
Melatonin falls just before you wake up. If melatonin stayed high, you’d keep sleeping. The bright light of the morning tells the brain to lower melatonin levels.
This cycle should align perfectly with natural sunlight cycles: when the sun is up –> melatonin is down.
So, what keeps melatonin low during the day?
Light Controls Melatonin
Just as darkness causes melatonin levels to rise at night, bright light causes the opposite: melatonin falls sharply with bodily exposure to light.
Light Lowers Melatonin
When light enters the eye and hits the photoreceptors on the skin, melatonin levels drop instantly.
When melatonin falls, humans feel alert and awake.
Darkness Raises Melatonin
Anytime the body perceives darkness, melatonin begins to rise.
Less Light Means More Melatonin
Over time, the repeated daily and nightly cycles of light and dark “entrain” the brain to know the time of day — and, therefore, the level that melatonin should be produced.
The Broken Melatonin Cycle
Melatonin Cycles Are Weakening
Modern lifestyles undermine the melatonin cycle at every turn, and from every angle.
Low Melatonin, Poor Sleep Quality
When evening melatonin production is harmed, sleep quality suffers.
Even if a person falls asleep quickly and sleeps through the night, that sleep is less restorative and healing.
In a 2010 study, normal room light in the evening harmed the melatonin response all night.
“Compared with dim light, exposure to room light before bedtime suppressed melatonin, resulting in a later melatonin onset in 99.0% of individuals and shortening melatonin duration by about 90 min.”https://www.ncbi.nlm.nih.gov/pubmed/21193540
The Brain’s Clock
The Suprachiasmatic Nucleus (SCN).
The SCN is the brain — and entire body’s — clock.
The “SCN” Controls Melatonin
It tells the brain what time of day it is — 24/7. This area of the brain works non-stop to keep the entire body functioning on schedule and in sync.
In the evening, the SCN tells the pineal gland when to start producing melatonin — and when to stop producing melatonin.
The SCN interpets the intensity and wavelengths of light that enter the eye and uses them to determine the time of day or night.
The SCN constantly tells the pineal gland how much melatonin to produce. The effect is immediate, with melatonin levels rising and falling quickly in response to light stimuli — or the lack thereof.
Bright Light Before Bed
STUDY: “Room Light” Before Bed Lowered Melatonin In 99% Of Individuals
Researchers studied 116 test subjects, exposing them to either “normal” room light or dim light in the hours prior to bedtime.
The results were clear: 99% of test subjects experienced a “profound suppressive effect on melatonin.”
This melatonin reduction delayed the body’s perceived window for sleep.
What’s more, when room light was present during sleeping hours, melatonin production was reduced by greater than 50% (in 85% of subjects).
Brightness & Color
Blue Is Bad At Night
Blue light lowers melatonin much more than red light — even 100 times more than red light.
By contrast, red light — even when extremely bright — will only lower melatonin a small amount. Weak, dim red light will have almost no impact on melatonin levels.
Even an incredibly tiny amount of blue light can significantly lower melatonin levels in the brain.
Green Light Has A ‘Medium’ Effect On Melatonin
Green light lowers melatonin at about half the rate of blue light — which is way more than red light.
“Our results suggest that we have to consider not only blue light when predicting the effects of light on our circadian rhythms, hormones and alertness, but also other visible wavelengths such as green light.”Steven Lockley, PhD
Virtually zero effect
Lowers melatonin some.
A powerful reduction in melatonin.
Good Light & Bad Light
Light affects the melatonin cycle — for better or worse.
Good light reinforces your melatonin cycle — making it stronger.
- Sunlight is the best form of “good” light. It is bright, its color temperature changes perfectly to guide the brain’s melatonin levels throughout the day.
2) Incandescent Bulbs
- Bright incandescent lamps are the best source of healthy light during the day. Halogens are just as good.
- These bulbs can provide moderate amounts of visible light in balanced ratios — helping the circadian rhythm.
- Incandescent & halogen bulbs are also safer for our eyes, skin, and hormones (than LEDs and fluorescents).
Bad light disrupts your melatonin cycle — making it weaker.
1) Darkness During The Day
- A dark room — in daytime — mimics nighttime and tells your brain to immediately make more melatonin.
- This undermines the natural circadian rhythm.
2) Bright Rooms At Night
- Being close to fluorescent and LED lighting after sundown, or looking at bright screens at night tells your brain to “wake up” — and reduce its production of melatonin.
*Technically, fluorescent and LED lighting is quite unhealthy during the day, as well, but for reasons other than the circadian rhythm.
(2) Darkness At Night
Complete darkness at night allows melatonin levels to rise optimally.
Optimally, we reduce exposure to bright and blue light several hours prior to bedtime.
For extreme circadian retraining, it can even be helpful to spend an hour in complete darkness prior to bedtime.
The further the effort toward evening darkness, the deeper the benefits, and the more likely the circadian rhythm will be properly restored and maintained.
A strong circadian rhythm often takes weeks and months to develop. Once strong, though, the circadian rhythm can become robust — bouncing back more and more quickly after interruptions.
However, the benefits of great circadian rhythm habits can be noticed in only a few days or a few weeks.
The deeper we dive into circadian health, the deeper the benefits.
Each and every light source has a “color temperature” — which is rated in Kelvins.
Color Temperature = Kelvin
Color temperature describes the ratio of blue to red.
The higher the Kelvin, the more blue. The lower the Kelvin, the more red.
Low Kelvin is described as being warm, while high Kelvin is cool.
Above 4000K is very high color temperature, and too high for evening light.
Sunset / Sunrise
Screens are extremely bright: 6500-9500 Kelvin.
Red wavelengths are dominant. Light looks more red, orange, or yellow.
Blue wavelengths are dominant. Light looks more white, or even blue.
White light is extremely high in blue wavelengths.
While artificial white light is rich in blue light, it is deficient in red light.
Sunlight’s Changing Color Temperature
With the exception subtle fluctuations (and solar flares) that don’t affect humans day-to-day — the sun actually produces the same light non-stop.
But the light that reaches the ground is always changing according to these variables:
In the morning, nearly all blue light is filtered out by particles in the atmosphere, leaving only the rich reds and oranges to reach the ground.
The Day Begins & Ends In Red Light
Sunrise and sunset both lack blue light.
The first and last few hours of each day have a unique, warm light signature. This warm light signals for your brain to transition to the next phase of your circadian rhythm.
Sunlight’s naturally changing color temperature (controlled by the angle of the sun) perfectly sets the brain up for powerful sleep cycles.
Morning sunlight has virtually zero blue wavelengths — hence it is warm and red.
By contrast, solar noon is rich in blue light — signalling to the brain: “It is mid-day!”
As daytime sunlight retreats, the brain knows nighttime is approaching. Melatonin rises in preparation for deep, restorative sleep.
Movement & Meal Timing
Movement clearly signals “daytime” to the brain.
Therefore, to further synchronize the circadian rhythm, daily movement is an important variable.
Gentle, “zone 2” exercise is perfect for sleep: Not too intense — just enough to get the blood pumping, burn glutamate, and lower melatonin.
Exercise and movement suppress melatonin secretion. Therefore, it’s best to exercise during the day — while the sun is up — rather than later in the evening.
Morning is the optimal time to exercise, but midafternoon is fine as well.
For many, if late in the evening is the only viable option, it may be best to go ahead and exercise in the evening. In these (hopefully rare) situations, late evening exercise that is very intense may be best for melatonin levels.
When you eat really, really matters for quality sleep.
It’s not necessary to be perfect with meal timing, but the earlier you eat your meals, the better for sleep and the circadian rhythm.
Getting these steps wrong can seriously impact the quality of your sleep — and your health.
Light tells the brain it’s daytime — and so do eating and movement. Darkness tells the body it’s nighttime.
It’s important to get the right amount of exercise — and then eat enough calories to support that movement. Whenever possible, great care should be taken to ensure meals are eaten a little early rather than a little late.
Eating Early Helps The Circadian Rhythm
Eat a real breakfast within a half hour of waking.
“We’ve inhabited this planet for thousands of years, and while many things have changed, there has always been one constant: Every single day the sun rises and at night it falls,” Dr. Panda said. “We’re designed to have 24-hour rhythms in our physiology and metabolism. These rhythms exist because, just like our brains need to go to sleep each night to repair, reset and rejuvenate, every organ needs to have down time to repair and reset as well.”https://www.nytimes.com/2018/07/24/well/when-we-eat-or-dont-eat-may-be-critical-for-health.html
At night, the lack of sunlight prompts the brain to release melatonin, which prepares us for sleep. Eating late in the evening sends a conflicting signal to the clocks in the rest of the body that it’s still daytime, said Dr. Peterson.https://www.nytimes.com/2018/07/24/well/when-we-eat-or-dont-eat-may-be-critical-for-health.html
Be finished eating for the day — fully supplied with sufficient calories to last the night — by a reasonable time in the evening.
There are certainly other factors that are important for the circadian rhythm, such as EMF, air quality, the state of your bedroom’s temperature and location, and more — and these will be discussed in the following pages of the Sleep section.
However, keep this in mind about the importance of light for the circadian rhythm:
If your light exposure is poor, every other step toward health will be less effective.
This completes ‘Understand Sleep.’
To continue, select ‘Morning Sunlight.’
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