The home my grandmother was born in had no electric lights. Night was dark. It’s easy to forget the universal truth of darkness after sunset when we now have 24/7 access to bright light at the flick of a switch.
Light and the Rhythms of Nature
Until about one hundred and fifty years ago the rhythms of day and night, sunrise and sunset were gentle and graceful. Our bodies evolved within this elegant pattern of nature. Human circadian rhythm is our internal clock and sunlight winds the dial.
Today, at least to our retinas, the sun often never sets. At 6 a.m. the alarm blares and the room is ablaze with light as bright as the sun. Our bodies barely notice when the sun sets. We cozy up inside our homes all aglow with dozens of bulbs, computers, tablets and smart phones.
Before we talk about how a bulb might keep you from aging, let’s have a quick science lesson about Kelvins and cortisol.
Color Temperature (Kelvins)
Light color temperature is measured by Kelvins (K). On the “warm” end 2,700 Kelvin light appears yellow and is close to the color of a candle flame or sunrise/sunset (1,850K). On the “cool” end, daylight is 6,500K and appears white or blue.
Hormones and Your Internal Clock (Cortisol and Melatonin)
Two primary hormones tell your body when it’s time to wake up and begin the day and when it’s time to retire for a long night’s sleep: Cortisol is the morning/awake hormone and melatonin is the sleep hormone. Take a plane trip across several time zones or work the night shift and you’ll feel the role these hormones play in syncing your internal sleep clock.
The Wrong Light Can Smash Your Body Clock
Every day for millions of years the sun has played an important role in resetting and winding our body clocks. Our bodies evolved to read the color temperature of the day and night and adjust the release of our sleep-wake hormones accordingly.
Now, regardless of time of day, we expose ourselves to a variety of light-bulbs and electronic gadgets on every end of the Kelvin color temperature scale. This exposure could be the hammer smashing our body clocks to bits.
Your laptop, iPhone, and iPad all have a color temperature that mimics daylight: a very cool 6800 to 7300 Kelvins. Whereas our great-grandparents may have never, ever been exposed to sunlight after sunset, we are now regularly staring into a daylight equivalent electronic screen.
A growing body of research supports the idea that this may be inhibiting the production of melatonin, and promoting sleep disturbances. Two recent New York Times articles reported on light’s impact on aging and disease.
Happy Light When the Time is Right
I’m now calling for a lighting revolution. One that might just help keep us young. At very minimum it will help us be alert during the day and encourage sleep at night.
The good news is that it is easy to control the temperature of lighting in your home and at work.
Complaints about new energy efficient light bulbs are due to poor labeling of packages to indicate color temperature. Incandescent lights are a warm 2700 Kelvins. Compact fluorescent lights and LED lights come in a variety of color temperatures. The wrong bulb can literally mess with your head.
Thankfully, there is a new Light Facts label that will help you easily identify the color temperature and help you buy the proper light bulbs for every setting. (For more information about bulb labels and how to choose the right bulb for each room, read my article “Nutrition Facts for Light Bulbs“)
Tips for lighting that makes your body happy:
Light rooms by time of day that they are most used. Warmer temperatures for living room and bedrooms where relaxation is essential. Cooler temperatures for laundry rooms, garage, workshops or kitchen where alertness is important.
F.lux makes the color of your Mac, Linux, Windows, iPhone or iPad display adapt to the time of day, warm at night and cool like sunlight during the day.
Photo via DTE Energy
Matt Grocoff, Esq. LEED is founder of Thrive - Net Zero Energy Consulting Collaborative, host of Greenovation.TV, a contributor to The Environment Report on Public Radio, the green renovation expert for Old House Web, and a sought after lecturer. His home is America’s oldest net-zero energy home and was called “Sustainable Perfection” by The Atlantic, honored as one of USA Today’s “Seven Best Green Homes of 2010″ and Preservation Project of the Year. He has been featured in hundreds of publications and news shows including Washington Post, Detroit Free Press, Preservation Magazine, Solar Today, Fox Business News, Huffington Post and more. Join him on Google+, Twitter and Facebook