Have you ever had trouble falling asleep at 2am after binge watching the latest season of House of Cards? Ever pulled an all-nighter then felt strangely awake and alert after walking outside into broad daylight? Ever spent all day at the beach only to sleep like a moss-covered boulder later that night? It probably comes as no surprise that light has significant effects on the human body. In fact, light and health researcher Talieh Ghane is convinced that human biology is the next big thing in lighting design, technology, and policy.

According to Ghane, light is actually a public health issue. Current policies focus on the visual aspect of lighting at the expense of the biological aspect—”because we don’t see it, it’s not tangible.” According to current scientific research, light takes two separate pathways when it hits the eye: the visual pathway and the biological pathway. While we know a lot about the visual pathway, research on the biological pathway or system is still in its early stages.
 


The Visual System and the Biological System 

Basically, scientists discovered a group of photoreceptors in the eye called intrinsically photosensitive Retinal Ganglion Cells (ipRGCs for short) that have less to do with what we see and everything to do with the body’s physiological response to light. These cells are dedicated to communicating important signals to the body, like when to go to sleep and when to wake up—our 24 hour body clock. Our circadian system, in turn, controls important bodily processes like hormone production, digestion, melatonin secretion, muscle strength, the rest-activity cycle, core body temperature, immune response, and more.

And while the visual system “responds to light in a fraction of a second,” the biological system is cumulative in nature and takes into account a diversity of factors such as the timing, color temperature, and intensity of the light, plus a person’s history of light exposure and their age—among other things. We do know that exposure to blue light has profound effects on human health and the circadian system. There is more energy in the cooler or bluish part of the color temperature spectrum (think high intensity daylight) versus the warmer or reddish part (think candlelight or campfires).

 
Artificial Lighting and the Circadian Rhythm 

Humans evolved to respond to high levels of blue light during the day, and virtually no blue light at night. However, with most of us spending the majority of our time indoors during daylight hours and the advent of artificial lighting— not to mention the high level of blue light emitted by electronic devices like cell phones and smart TVs—the body doesn’t know how to respond:

Our body is confused because it doesn’t know when it’s day and when it’s night. During the day we don’t get that much of the intense light that you’re supposed to get if you’re in nature. And at night when you’re not supposed to get any blue light, you get a lot of blue light.

Researchers have linked unhealthy amounts of blue light at night and the disruption of the circadian system to an increase in cancer rates, infertility problems, retinal degeneration disease, and diabetes.

Ideally, humans would be exposed to the dynamic range and intensity of light in the great outdoors, like our Netflix-less ancestors. But even though that’s rarely possible in this day and age of lighting fixtures and constant facebooking, we can still embrace healthy lighting habits in our day-to-day lives. 

Ghane offers seven tips for health lighting for those of us who are not lumberjacks or carnies. 

7 Tips for Healthy Lighting

1. The first and most important: Try to get at least one to two hours of high intensity blue light during the day (ideally two hours after you wake up). This helps to reset your circadian system. It can even help you “cheat”—if you work high intensity light into your daytime schedule, you will be less sensitive to blue light later in the day when you’re trying to get in some quality screen time right before bed. Not that you should do that or anything.

2. At night, have your room as dark as possible, because “Healthy lighting goes hand in hand with healthy darkness.” Invest in blackout curtains. Turn off electronic devices. Unplug that nightlight.
 
3. Log off electronic devices two hours before bed. Read a book.
 
4. If you need to work or study late at night, wear glasses that decrease the amount of blue light (these are usually amber-colored).
 
5. Alternatively, download an app like f.lux to your computer/tablet/phone. It will reduce the amount of blue light coming from the screen.
 
6. Get outside. If you’re at the office, take your lunch break outdoors or at least sit by a window. We spend over 90% of our time inside, and even 30 minutes to an hour of sunlight a day can make a huge difference in maintaining a healthy circadian rhythm.
 
7. Invest in high CCT lighting. LED fixtures can can be programmed or adjusted to match the dynamic range and intensity of daylight.
 

A few simple changes in your day-to-day life can make all the difference. For a more in-depth take on lighting and health, you can check out the full interview here.

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