The Ultimate Guide to Lighting: How to Improve Sleep, Productivity, and Health with Light
“Lighting is everything. It creates mood and has an emotional effect on you.”
-Zak Bagans
The most effort people put into thinking about light bulbs is usually “How quickly can I replace that one that burned out?” You find a few bulbs, compare prices, replace it, and store the rest in the basement. This is a reactive approach that 99% of America probably has it makes total sense. Just give me light so I can see. But what if that new light bulb is the reason you're so tired in the morning, the reason you have low energy during the day, or even the reason you have cancer.
Light may be one of the most important and most overlooked factors influencing our body and our mind on a second-to-second basis. Everyone has heard about the issues with blue light and most people recognize that sunlight is good but beyond that, there’s little awareness of how influential the lighting around us is.
Our ancestors had it easy by waking up when it was light out and going to sleep when it was dark out. A perfect circadian flow followed and set the evolutionary precedent for us. We modern humans now spend 93% of our time indoors meaning that if we want to function well we have to do some work to avoid blue light at night and get in sync with the sun’s revolutions. Let's dive in.
Why is Light So Important?
Lighting, like water and sleep, is a universal element that every human of every ethnicity has evolved with since the beginning of life on Earth. Trends like diets, exercise routines, and stress management tools fall into a less-universal bucket because every ethnicity has used them differently and, therefore, people evolved to respond differently to these elements. While ancestors of Subsahara Africa, Japan, and Uruguay all respond differently to a low-carb diet and marathon training, they all respond to light in very similar ways.
So how exactly does light impact us?
In the morning our cortisol levels are high (which is why you tend to wake up at certain times naturally) and melatonin levels are low. As the day progresses these hormones switch so that melatonin is high in the evening and cortisol is low. This inverse relationship is important for a healthy sleep-wake cycle. The wavelengths of the sun hit your retinal photoreceptors (rods and cones) which are then processed by your ganglion cells in the brain. So what about those who are blind or visually impaired? Turns out that we mammals not only have the standard photoreceptors but we have “non-image-forming ocular photoreceptors” in retinal ganglion cells of the eye This exposure to blue light is so important that we evolved to activate the cognitive benefits of light even when we couldn’t see it.
The Benefits Of Blue Light
Blue light gets a bad rap. There’s a push to block out more and more blue light to the point where blue light blocking glasses are being used in standard eyeglasses. This approach to blue light is throwing the baby out with the bathwater. (Remind you of any popular 90’s food diet trend that didn’t look at all of the evidence?)
I wrote about the effects of blue light on sleep in the article “8 Behavioral Sleep Tactics for the Perfect Night of Sleep” but I’ll elaborate on it here. With blue light, it’s less a matter of good or bad and more a matter of when. When your eyes are exposed to blue light in the morning, this promotes the high cortisol-low melatonin balance and increases alertness, improves mood, performance, and concentration, and decreases irritability. Early blue light exposure also improves sleep quality and reduces daytime sleepiness. In fact, scientists put these blue light benefits to the test against something else that also provides these benefits: coffee.
In one study, participants trialed four scenarios of white light, caffeine (240mg), blue light, and a placebo on different days. It looked at the psychomotor effects of each and determined that caffeine and blue light both improved visual reaction, however, the blue light came out on top for accuracy and executive functioning skills while distracted. It further suggested looking into blue light as an athletic performance enhancer.
For millions of years, this exposure to light has been our only cue that impacts circadian rhythm. This type of cue is also known as something that sounds like a German superhero, a zeitgeber. Lighting, along with other less powerful zeitgebers like food, movement, and social interactions, told the “master clock” of the body (the suprachiasmatic nucleus) that it was time to get up and move or it was time to start winding down and resting.
Early sun rule of thumb. To get these benefits it’s important to get sunlight to your eyes and as much of your skin as you can (without creeping out the neighbors) first thing in the morning. The minimum effective dose is 10,000 lux. On a sunny day, this only takes a minute of exposure and on a cloudy day, it could be up to about 30 minutes. I check the lux on cloudy days every once in a while using the Lux Meter app. If you can't get out first thing in the morning then do it before 10:00 a.m. And if you can’t get outside at all then use a light therapy lamp.
The Downside Of Blue Light
Now, fast forward to the 1800’s when one of the most important human inventions came about: artificial light. This incredible invention is found far and wide: our cars, homes, computers, cell phones, watches, remote street corners, airplanes, and even satellites in orbit. Two hundred years ago it was impossible to find artificial light and now it’s nearly impossible to avoid it.
But why would we want to avoid it? The answer comes back to our circadian rhythm. When our eyes and the rest of our bodies are exposed to blue light in the morning it does wonders. When we’re exposed to blue light in the evening it wreaks havoc. We depend on melatonin production for a good night’s sleep and this melatonin production is inhibited when our eyes and bodies are exposed to blue light because our minds are tricked into thinking it’s daytime thanks to those millions of years of programming. While our body needs a ton of blue light in the morning for a charge, even a little bit of blue light in the evening crushes us. All evening “junk light” (blue and green hues that disrupt sleep) is bad but the worst type of lighting is fluorescent lighting at night which basically vaporizes the melatonin from your bloodstream so avoid gas stations, supermarkets, and the Vegas strip in the evening.
Lighting before going to bed is known to impact our sleep but what about light when we’re already in bed? A study compared participants exposed to 3 lux (extremely dim light) and those exposed to 100 lux (comparable to a very dark, overcast day) for one to two nights. While melatonin levels were equal in both groups, those exposed to the 100 lux had less time in slow wave and REM stages of sleep, higher heart rate, lower heart rate variability (HRV), and even higher insulin resistance numbers. They concluded that “avoiding exposure to light at night during sleep may be beneficial for cardiometabolic health. (Pro tip: put up the blackout shades in the bedroom and keep the phone in the bathroom at night.)
Light impacts our cognition, metabolic health, fat cells, our immune system, mood, and hormones like testosterone. So, naturally, this evolutionary mismatch of blue light in the evening leads to downstream health consequences like sleep disruption, increased risk of cancer, obesity, heart disease, and a shortened life expectancy. With more people scrolling social media while watching TV while using their tablet while looking at their smartwatch later and later into the night, it’s no wonder that America is waking up groggy and sick.
Blocking Blue Light
The obvious answer, then, is to just turn off our artificial lights and use natural light like candles within a few hours of bedtime. But this is like asking a fish to swim without water. Modern humans just can’t do it so let’s avoid that rabbit hole and go through door number two.
The next easiest step, then, is to use blue light blockers to prevent blue light from hitting your eyes. A study on those with insomnia showed that using blue light-blocking glasses (both amber ones and clear ones) improved the length of time slept, total sleep time, and the quality of sleep when wearing them for 2 hours before bed. It’s best to wear these glasses at least 2 hours before bedtime. Blue light blocking glasses are generally broken into two categories: clear and amber. Clear ones block out a maximum of 50% of blue light while amber ones block up to 99.8% of all blue light. These are the best options:
Best tinted ones: Essential Living or Spectra479 (the best on the market, blocking 99.82% of blue light)
Best clear ones: Felix Grey
There are other measures to take against the evil blue light at night too, and for good reason. A study found that living near street lights significantly increases your risk of cancer. Even the blue light coming through your windows at night when you’re sleeping has an impact on you. Use blackout curtains to block this but also be mindful of the blue light in your room. Lights that look weak and benign in your room also have the potential to affect your sleep. Use electrical tape to cover up lights on your TV, humidifier, chargers, etc. And use a sleep mask for good measure.
What to Look for in a Lightbulb
The next strategy is to modify the lighting in your home. This takes some upfront work but it decreases the friction for the remainder of the time you’re living in that house.
When I first learned about the importance of changing the lighting in the house I thought it would be as simple as putting red lights in the bedroom and bright lights in the living room. Then I went an inch wide and a mile deep into the science of lighting. I took what I learned and (with some eye-rolling from my wife) modified the lights in our house accordingly. This next part breaks up the different parts of lights and the lightbulbs themselves but if you aren’t one for geeking out then skip down to the next section for the practical tips.
In order to find lights that mimic natural light (for the daytime) and ones that minimize blue light (for the evening), there are four parameters that need to be considered: Color Rendering Index (CRI), the temperature of the light (expressed in Kelvin (K)), the wavelength, and the amount of flicker.
CRI. The color rendering index (CRI) is the ability of the light source to reveal the colors of objects compared to natural lighting. Candles, sunlight, and incandescent bulbs all have a CRI of 100, fluorescent lights are in the 50-85 CRI range, and low-pressure sodium bulbs are at the bottom of the list with 5. A device called a spectrophotometer measures the light reflected from the source on a scale of colors. R9 is the color red so when looking for red lights for nighttime, look for a full red spectrum of R9.
Color temperature. Color temperature (a.k.a correlated color temperature or CCT) is a way to measure the appearance of lights. Every color falls on a spectrum from orange to blue and it’s quantified through Kelvins (K). Candles have a color temperature of 1,000K, early sunrise is 3,500K, and daylight sun is around 5,000-6,500K. LED bulbs have a temperature range between 5,000-6,500K+ (for “daylight white”) but opting for “warmer” LEDs can get them in the 2,700K range. Incandescent bulbs have a max of 3,000K.
Wavelength: Every color on the electromagnetic spectrum has a different wavelength. Human eyes can only see the ones between 380 nanometers and 750nm, this is called the visible spectrum. Blue light has short wavelengths between about 450nm to 495nm. Red light has longer waves, with wavelengths around 620nm to 750nm. To ensure that the color lightbulb you are choosing is actually the color you want you can use this as a guide. Be careful when only using your eyes to determine whether a light is red or blue because technically red-looking lights can have lower wavelengths or vice versa for blue lights. Lighting products don’t always identify the wavelengths but don’t immediately opt out of a good light if you don’t see the wavelength listed.
Flicker. Flicker is the rapid change between the red, green, and blue colors that are constantly happening on LED systems (smartphones, monitors, lights). You can see this when you hold your phone’s video camera up to a monitor. Without this trick, though, we don’t consciously see a flicker although our retinas are constantly sensing it. In the short term, this causes eye strain, headaches, and sleep issues. In the long term, it causes cataracts, cardiovascular issues, and potential permanent retinal damage.
The Best Lights To Choose
The ideal lighting option during the day is natural light, whether that's direct sunlight, light through the clouds, or sitting in the shaded area outside. This is far from realistic for most of us so fortunately there are artificial options that mimic this natural light. I see a future where smart lightbulbs will replicate the features of the sun based on the time of day. Until then we’ll have to do it ourselves.
In fact, NASA is in the same boat as us. It’s only been in recent years that they’ve replaced their fluorescent LEDs with lights that don’t emit blue light near bedtime once they realized that their astronauts weren’t getting enough sleep. Here on earth, the best way to utilize a healthy lighting system is to break up rooms into two zones: day and night.
The Day Zones
The day zones of the house or office will consist of areas you use during the day and which benefit from naturally high ranges of cortisol and alertness such as the kitchen and the office. For this zone, it’s best to use flicker-free lighting that mimics the early sun around 2,700K.
Day Zone Bulbs: 2,700K flicker-free lightbulbs with a high CRI (we use Philips LED flicker-free lightbulbs)
If you want to use lighting as a performance enhancer and productivity booster like the studies above then using a stronger light that mimics the midday color temperature of the sun (5,000K) is ideal. I’d recommend doing this for no more than 2-3 hours a day and no later than 1 or 2 pm or else the light could throw off your circadian rhythm and make it difficult to transition to the evening slump as melatonin rises. Place the bulb in a lamp you can easily turn off after a few hours or use a reading lamp like this that has dual mode temperatures of 1,600K for nighttime and 5,500K for productivity mode. You can also get a big jolt of energy from a light therapy lamp.
Day Zone Productivity and Alertness Bulbs:
5,000K flicker-free lightbulbs with a high CRI (like the Philips LED flicker-free lightbulb)
5,500K Hooga reading lamp
What I do: I work as an OT in a rehab facility where I have minimal control over the lighting in the area. I take advantage of what I can control by sitting at a desk with a window to the outside, opening up the blinds in the treatment area, and trying to treat all of my patients near natural light. During workdays, I also walk outside before work, at lunchtime most days, and I spend time in the sunlight with my kids after work. During the winter I use a light therapy lamp as I drink coffee and write. During the days I don’t work I’m outside as much as possible and under the “day zone” bulbs in our home.
The Night Zones
The night zones of the house are those used in the hours before bed and during bedtime when you want to keep melatonin high such as in the bedrooms and the bathrooms. The best option for this zone is candles since they are natural, flicker-free, and have a low color temperature without a strong red glow.
When looking for candles, avoid:
Paraffin (which gives off benzene and toluene which are carcinogenic and toxic)
Soy (since most soy is genetically modified).
Lead wicks (can be toxic with chemicals as well)
Colors and dyes
Synthetic fragrances (which contain plenty of chemicals like phthalates, formaldehyde, and other endocrine disruptors). (Source)
Instead, opt for candles made of beeswax like these. If you prefer a scent, then go with beeswax candles made with essential oils like these.
After candles, the next best option for lighting at night are the products below. The CRI number for nighttime use is less important while the temperature and the flicker are most important. For some reason, night lights are much less likely to list any lighting parameters so choose carefully.
In doing research for the best products I’ve also found that plenty of manufacturers claim that they make red lights for “natural” and “healthy” nighttime use but they either don’t quantify the parameters above or the parameters are anything but “healthy.” Since these vague terms don’t require regulation, do your research.
Lightbulbs
The Best:
TrueLight Luna Red Sunset Light (1,000K-3,000K, flicker-free). Great but expensive.
Runners Up:
SuperWarm bulb (1,700K, flicker-free)
Neporal amber lights (1,800K, flicker-free). This is what we use in our bedroom.
Bedtime Bulb (2,200K, unknown flicker). This is what we use in my son’s bedroom.
Night Lights
The Best:
SerieCozy Red Night Light (800K)
Runner Up:
Luna Red Light (1,001K, 100% blue light free, 658nm). It is motion-sensored and has dusk ‘til dawn sensing as well. It can also toggle between a flashlight and a nightlight.
Emagine A Nightlight (no data listed). This claims that there is zero blue light but it’s not quantified anywhere else. This is the one we have been using in our kids' room for years. It’s light enough to get bottle feeds in while still allowing them to get back to sleep quickly. It’s dim enough that reading a book isn’t easy though. We also use a hallway one so we could get back to sleep quickly too.
Sunrise Alarm Clock
Jall Wake Up Light Sunrise Alarm Clock. There’s no data on the lighting parameters of this but we have been using this successfully with our son on school days. You can set the light to gradually increase from 10, 20, or 30 minutes before the alarm period with varying brightness levels of 10%-100% (which is really bright). And you can use natural sounds like birds chirping as the alarm.
Note: The bulbs mentioned above are different than those used in red light therapy. These bulbs are great for ambient lighting and they do not have the wavelength to promote photobiomodulation (more on red light therapy another time).
Takeaway
Lighting is an incredibly powerful tool that directly impacts your circadian rhythm and has many downstream effects on your health, mood, and performance. Whether it’s in the home or office, modifying your environment to mimic natural light is the best approach for healthy living. Break your environments up into day zones and night zones. For day zones stick with warm lights that contain blue lights and for night zones use red lights to mimic evening time.
Plenty of people go through life saying “I’m a bad sleeper.” While this is probably true, the more holistic statement is probably along the lines of “I don’t use any proactive approaches or environmental modifications to allow my mind and body to get adequate sleep so I sleep terribly as a result.” Start by getting out in the sun and buying some lightbulbs.
How do you use light to your advantage? How does light impact you?
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