You may have heard of our ‘circadian clock’ - it’s the term we use to describe the body’s natural rhythm. As an owner of a human body, you know how hard it can be to stay up all night - it’s difficult even for those who have partially acclimated, like shift workers or flight attendants. We’re diurnal animals.
Similarly, if you exercise with any regularity, you’ve probably found that there’s a sweet spot for you somewhere, likely when the sun is up - a point at which your body feels most ready for action. Even if you haven’t pinpointed it, you probably think most clearly around the same time of day every day as well.
You may also be aware that your body regulates its functions with a steadily-changing cocktail of hormones and neurotransmitters, and many of them are involved in the management and reinforcement of your circadian clock.
Source: Wikimedia commons
What you may be less aware of is how directly this internal cycle is affected by the light that hits your eyes.
Knowing this, you should know that by simply manipulating the color and intensity of light in your environment you can control a lot of your body's natural cycles.
In this article we’re going to look first at specifically which colors elicit responses from the body, and then we’ll take a look at 7 practical ways you can use this information to be alert when you want to, wake up more refreshed, and fall asleep reliably at bedtime.
Blue light at frequencies of ~460-480 has been shown in fMRI studies to activate parts of the brain associated with increased norepinephrine levels. Norepinephrine, also known as noradrenaline, is a neurotransmitter responsible for mobilizing the brain and body for action, and its cycles are closely tied to the body’s circadian clock.
“In the brain, norepinephrine increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, and focuses attention; it also increases restlessness and anxiety. In the rest of the body, norepinephrine increases heart rate and blood pressure, triggers the release of glucose from energy stores, increases blood flow to skeletal muscle, reduces blood flow to the gastrointestinal system, and inhibits voiding of the bladder and gastrointestinal motility.” (Source)
A related study to the one above even found that the effect on our bodies’ circadian clock from 460nm (blue) light was twice as profound as that of 555nm (green) light of equal photon density, and caused double the melatonin suppression.
Melatonin you may recognize as the sleep-wake hormone released by our pineal glands to tell us to get in bed and stay there - the same one that shows up late, or early, depending, when you’ve taken a long flight, causing symptoms of jet lag. ‘Jet lag’, of course, is just a name for how it feels when you go where your body’s clock is set wrong.
Geek side note: the study referenced above used photon density as a measure of effective light intensity and makes the argument that the commonly-used lux unit (a measure of illuminance over area) fails to capture the relationship between discrete photons and neuronal signaling that occurs in the eye. Interesting stuff!
Perhaps as intriguingly, this blue frequency band that activates our bodies and minds does not correspond with the maximum sensitivity of the discrete photoreceptors in our eyes - our rods are activated at ~505nm and our cones at ~430, ~530, and ~560nm. In fact, our entire three-cone visual photopic system’s sensitivity peaks in the green band at 555nm (which is the explanation for a bevy of other fascinating optics, biology, and video compression rabbit-holes we won’t go into here.)
Visible Light Spectrum - Source: Wikimedia commons
One could speculate that the attunement of these ‘energizing’ portions of the brain to the blue spectrum (commonly defined as the band from 450-495nm) is to reinforce diurnal behavior and human circadian rhythm — what color is the sky in mid-day? ~480nm! Every schoolkid knows that.
So we walk outside, the bright blue light hits our eyes, moves along some special wiring we don’t quite understand yet, activates the locus coeruleus-norepinephrine (LC-NE) system, the last melatonin from the night before gets washed away, and we’re awake as we’re going to get.
At least, this is how it’s supposed to work.
Of course, as a modern human, you’re around all sorts of sources of blue-ish light at all times of the day, whether from your phone, your computer, your TV, the lights in your home, in a brightly-lit restaurant, or even the headlights of cars you pass on the way home after dark.
Paradoxically, even surrounded by all these sources of blue light, many of us don’t actually get enough of it, or at least not sufficient intensity, to establish a healthy ‘on’ part of our circadian schedules, especially if we live in poorly-lit spaces with little natural light or live far from the equator.
So, given that blue light has such a powerful effect on our bodies and minds, how do we use it to our advantage?
In simple terms - get outside in the morning and during the day! Alex has written about this in more detail in his article How to Improve Your Sleep With Morning Sunlight
As we covered above, blue light suppresses melatonin production and stimulates norepinephrine, basically tricking your body into thinking it’s mid-day. When you’re getting ready for bed, just like you don’t consume caffeine (you don’t drink coffee before bed, do you?!), you should avoid blue light, a practice known as ‘dark therapy’.
There are some simple, low-hanging fruit approaches if you’re just looking for a quick fix:
This is the big intervention we want to focus on - artificial lighting has been around for a long time but only recently has ‘cold’ lighting been widespread enough to be a significant source of concern for sleep disruption.
When we say light is ‘warm’ or ‘cold’, we’re talking about the temperature of the light, usually measured in kelvin units, representing points along a curve in color space known as the Planckian Locus, or black body curve:
Source: Wikimedia commons
Somewhat counter-intuitively, higher numbers on this curve are associated with cooler colors, so whereas 2,000 K is close to the color of firelight, daylight can be closer to 6500 K, and the clear sky can be in the range of 15,000 - 27,000 K.
Smart lighting (color-changing lighting) is currently better than it’s ever been, but there’s still no perfect product on the market.
A common smart light on the shelves worldwide is the Hue system. It’s made by Dutch LED giant Philips. Hue is available at a reasonable price point and has excellent reliability but leaves a lot to be desired in the realm of brightness and color fidelity. Hue’s color engine is RGB, which is good for saturated color like red but not so good for producing whites accurately - whites can often look distractingly ‘tinted’ and ‘off’ when made with an RGB light.
My smart lamp of choice is from Australian startup LIFX - their Mini Day & Dusk bulbs have about 800 lumens of light output and produce whites in the range of 1500 K to 4000 K without the strange tints associated with white light from an RGB engine.
As an upgrade, good for daytime living and office areas that need extra punch, their A19 lamps put out 1100 lumens across 2500 K to 9000 K plus have excellent RGB capabilities that let you fill out the later hours of the night with a nice deep red.
Speaking of scheduling - nobody wants to pull their phone out to change the light setting every hour, and it’s in scheduling that LIFX differentiates their offering. The native LIFX smartphone app allows users to make a four-point curve that controls the color temperature and brightness of their lights throughout the day automatically.
The four-point curve leaves a lot to be desired in the way of flexibility, and LIFX have notoriously poor reliability in the connectivity department, meaning at least once a day you’ll find a lamp or two left behind, stuck on the setting from earlier in the day, but it’s far better than anything else on the market outside of some very specialized purpose-built devices and some expensive and complicated commercial alternatives.
This is the LIFX iOS app showing the schedule I use in my office and the options available when editing one of the four points on the schedule.
You’ll see I’ve elected to use the span between the ‘Wake Up’ and ‘Day’ points to cover most of the working day, while saving the two spans between ‘Day’ and ‘Evening’ and ‘Night Light’ to make a graceful transition between cold working light and warm evening light. I don’t think this was the designers’ intent but I’m doing it for a reason.
Using the breakpoints as the names suggest they should be used, means you have really only a single long transition across the majority of the day, which either makes the transition from cold daylight to warm evening light quite abrupt. Or it means you have a daylong transition from cold morning light to warm evening light that gives very little control over what happens in the middle. Misusing the breakpoints like this helps solve that problem by giving more resolution to the evening transition.
Let’s take another look at that chart from above. I’ve taken the 24-hour circadian schedule and overlaid the color spectrum I’m aiming for when configuring smart lighting.
Some important points to note:
If you’re not a morning person, you may find wake-up lights helpful. These function like normal alarm clocks but in place of (or in addition to) some kind of audible alarm, they add a gradually-brightening light source.
There are loads of examples out there but if you want something with great aesthetics and powerful light output, I’ve had a good experience with Philips’ flagship version. It’s only rated to 300 lux but nested in a parabolic shape that throws a beam that reaches deep into the unconscious mind, even through closed eyelids.
Paired with the clock’s smooth dimming feature, it’s a gentle but insistent wakeup that slowly brings you to consciousness in a way that feels less intrusive and abrupt than a traditional alarm clock.
If you live in a part of the world far from the equator, you may experience seasonal affective disorder, or SAD, where a shortened circadian schedule from reduced light exposure contributes to a drop in serotonin, melatonin perturbations, even symptoms of depression or worse.
This can occur in the darkest winter months and can vary widely in intensity, manifesting in some simply as insomnia or craving for high-carbohydrate food, but can closely imitate major depression for those who have it worst.
While SAD is a diagnosis, symptoms of light deprivation occur on a spectrum. Just spending most of your days in an environment with limited natural light can lead to SAD-like symptoms.
Even if you’ve implemented one of the smart lighting systems discussed above, you may still find that their direct light intensity (or photon density entering the retina) is insufficient to combat SAD. For that reason, a dedicated blue light for short therapy sessions might be helpful.
Blue lights are generally arrays of ~480nm-tuned LEDs designed to shine indirectly into the eye. They frequently have a kickback stand so they can be placed on a desk at the corner of your field of vision, and a timer and intensity setting to help with dosage. Philips make a very usable version but there are many out there than can do the job.
When using blue light therapy, you want to be consistent with the time of day you use it, and if you’re using it for circadian reinforcement, it should coincide with what you want to be the middle of your productive day, probably between 12pm and 3pm.
You may see versions of the ‘energy light’ with a high-intensity white light, but, as we know from above, only the blue is doing the heavy lifting - the rest is wasted energy and rather blinding to be in front of.
Similarly, even if you have an RGB smartlight, simply setting it to a bluish tone will probably not do the job anywhere near as well as a tuned therapy light. This is because LEDs produce a discrete color spectrum that can lack entirely any light energy at a given frequency. It’s this comb-like, spiky frequency graph that explains the murky look of poor-quality LED lighting - this aspect is referred to as the color rendering index, or CRI, of a light source.
Even smart lights with high CRI, though, are unlikely to produce enough light energy where it counts to be useful as a purpose-built blue light, so don’t be surprised if you get poor results from a homebrew setup.
To get the most benefit from your lighting interventions, set yourself up to win by paying attention to how lighting makes you feel, and use the occasion of a lighting makeover to ditch some bad habits while making new ones.
For example, it’s common to self-medicate during the darkest parts of the year with increased caffeine intake, but caffeine’s role as an adenosine-receptor agonist means that it can delay the onset of sleep, delay REM sleep, and cause knock-on effects into the following day that lead you to reach for more coffee, a vicious cycle researchers have called the ‘sleep sandwich.’
Deep red light late at night can put you to bed right on time, and a light alarm clock can help you pop out of bed without snoozing the buzzer all morning, but if you misuse caffeine while trying out a circadian light schedule, you may come away thinking it ‘just didn’t work for you’.
SAD and circadian disruptions generally are also associated with cravings for fatty food - healthy adults were shown to eat more fat after a disrupted nights’ sleep in one study. Of course, anybody who has pulled an all-nighter knows that willpower can be supplanted by cravings when exhausted.
In a diabolical Catch-22, another study found higher fat and sugar intake associated with less restorative sleep. Another sleep sandwich!
Rather than reach for an extra cup of coffee or a donut in the afternoon, if you’re feeling like light, diet, and exercise still aren’t getting you through the post-lunch slump, consider supplementing with an adaptogen or non-stimulating nootropic - ideally something without caffeine that provides a degree of neuroprotection to counteract the biological stress associated with sleep disruption.
While total control of your lighting circumstances is the ideal, any one of the methods mentioned above could have positive effects on the way you feel and think during the day.
Replacing every lamp in your home with smart lights could be cost-prohibitive, and getting buy-in from your loved ones on using their phones as a lightswitch can be an uphill battle. As with anything, try interventions piecewise as they become feasible, and, most importantly, be mindful about how you feel every step of the way.
If you’re anything like me, getting set up with good lighting at night will turn you into an exquisitely sensitive ‘lighting freak’ who feels lighting like an emotion. More awareness to your surroundings is generally a good thing because it leads to more awareness of your mind and body.
Noah Norman is a developer, artist, and founder of Vernon Health, makers of Plato, a simple, natural nootropic.
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