Many of my friends ask for herbal tea after dinner when they come over for a visit. They’re tuned into how caffeinated tea or coffee at night makes it difficult to fall asleep. None of them, however, request that I dim the lights in the kitchen after dark. And, maybe they should. 

As diurnal creatures, we evolved to be exquisitely sensitive to the sun. In 2017, the Nobel peace prize went to Jeffrey Hall, Michael Rosbash and Michael Young for their discovery that every cell in our body has a circadian clock dictating when it should work and rest.  Without itself ever being exposed to the sun, an islet cell deep in the pancreas knows that it needs to secrete insulin during the day and decrease its activity at night. That’s because each cell is governed by a ‘master clock’ in the brain which is, itself, partially programmed by light entering the eye.

When sunshine hits the eye, the short, blue wavelengths stimulate the optic nerve,which transmits a message to the brain to suppress the release of a hormone called Melatonin. This, in turn, makes us more wakeful. 

Exposure to bright light in the evening has actually double the effect of caffeine in delaying our circadian clock and keeping us awake.

Researcher, Kenneth Wright, at the University of Colorado in Boulder has been conducting research on circadian rhythms in the absence of man-made light. Essentially, he takes people camping for weeks at a time and observes what happens.

What he’s seen is that exposure to sunshine in the mornings and a gradual light tapering when the sun sets in the evenings adjusts people’s clocks by as much as two hours. That means that someone who might normally go to bed at midnight, goes camping and is now able to fall asleep easily at 10pm.  Morevover, ‘night owls’ have the most dramatic normalization of their rhythms. In one of his reports, Dr Wright writes “We find that later chronotypes [night owls] show larger circadian advances when exposed to only natural light, making the timing of their internal clocks in relation to the light-dark cycle more similar to earlier chronotypes.”

Electrical light is a relatively modern invention and has allowed us to lengthen our daylight to read, watch movie, read blogs and many a wonderful thing. And, despite common myths, it remains unclear whether modern life has actually lead to shorter sleep duration. But, as Dr Wright demonstrates, light in the evenings has certainly delayed sleep onset for many of us. 

That may not be a good thing, especially for  sensitive individuals who are already prone towards later sleep onset and are forced to conform to early work start times. For those folks in particular and the rest of us too,  it makes a lot of sense to get reconnected with nature’s light and dark patterns. 

So, if you’re someone who has a difficult time winding down to go to sleep and then wake up feeling groggy try the following three things:

• Give yourself plenty of bright morning light
• dim all light sources in the evening (In our house, we even wear yellow goggles when doing any sort of evening screen time)
• meditate on the night sky (see meditation above).