New Tricks to Improve Sleep: Light

New Tricks to Improve Sleep: Light

Sleep Tips


Nothing here about avoiding coffee after noon.

Or taking Melatonin.

Or taking a warm bath before bed. 

Those tricks certainly work. But they are not new.

This isn't about supplements either. 


It's All About Zeitgebers


Zeit-geber. It's German for 'time giver.'

A zeitgeber is an environmental cue or trigger like light or temperature that regulates our internal clock. 


Light...At All The Wrong Times

It's not a surprise that light affects sleep. 

Humans are diurnal - active and outdoors during the daytime and at home in bed at night. 

Human 'night owls' are an artificial construct. A by-product of electricity, television, and now, handheld devices. 

I'm not talking about being a 'morning person' or an 'evening person.' That's normal genetic variation - some people wake up at 5 am bright-eyed and bushy-tailed. You know the type...they've already worked out at the gym, showered, and finished the laundry by the time you drag your sleepy a** out of bed.

I don't like those people. Especially before my morning gallon of coffee. 

Back to light. 

Light is a POWERFUL zeitgeber. 

Food, temperature, and activity are others. This article focuses on light. More on the other zeits in another piece. 

Even if you are not a morning person, light plays an incredibly important role in waking you in the morning and making you sleepy after sunset. 

Hundreds of years ago, before the advent of technology, we all synchronized our wake-sleep cycles with the sun.

Our bodies are meant to rise with the sun and get drowsy after sunset. 


Your Gut Bacteria Have Sleep-wake Cycles too

I don't mean your gut probiotics go to sleep at night...they die off at night and regrow in the early hours of the day! 

In people with healthy circadian rhythms, Lactobacillus reuteri numbers bottom out at midnight and peak around 4 PM.

Bacillus subtilis does this too, but it also responds to temperature differences in day and night - let that sink in for a bit for those of you living in permanently air-conditioned spaces. 

See the chart below from a fascinating study from Israel. I added the blue circles to note midnight. 

Probiotics and sleep

Source: Thaiss et al. Transkingdom Control of Microbiota Diurnal Oscillations Promotes Metabolic Homeostasis. Cell 2014: 159. 

So, what happens if you pull out that tub of Ben & Jerry's at 11 PM and start bingeing on a TV show? 

Well, light and food at the 'wrong' time give you jet lag. Whether you know it or not, you also mess up your gut probiotics. The end result is increased glucose intolerance and if continued on a regular basis, obesity. Not to mention poor cell and DNA repair. 

There is emerging evidence that prebiotic fiber can help speedier recovery from jet-lag induced gut dysbiosis. At least in mice, anyway.

Probiotics and obesity


Blame it on Netflix - (Just-One-More-Episode Syndrome)

Sure, the draw and addiction of a bingeworthy show on Netflix or Prime is powerful. 

Back in the 80s, Magnum, P.I. and Murder, She Wrote conveniently solved complex crimes in less than an hour. There were no cliffhangers until the end of the season. You could watch an episode and go to bed knowing that the bad guys got busted. 

Not so today.

Have you noticed how each episode on modern streaming shows end with a shockingly suspenseful story development? 

We all get sucked in. Just one more episode. I swear I'll go to sleep after that. 

It's Friday and you've earned a little me-time, right?

Revenge bed time procrastination is a thing. Especially among 9 to 5 working folk who are beholden to a boss' strict work schedule during the week.  

That hour of lost sleep is not the only thing I'm talking about. 


Melatonin-killing Blue Light

It's the exposure to melatonin-killing blue light from massive LED TV screens combined with the hyper-stimulating late-night entertainment that kills sleep.

We need darkness for an hour or two before bed (or at least dim or blue-free light like candles) to help the body release sleep-inducing hormone Melatonin. 

Bright lights, especially when combined with food, after sunset tells the body that it's wakey-wakey day time. 

When we were kids, we watched Angela Lansbury on small, dim TV screens. Now, TVs are HUGE! And ultra bright. You need shades when walking into a Costco, with all those giant TV screens aimed at you.

It's more than just blue light. Storylines are designed to be addictive and 'brain-electrifying'. 

Even after you've turned off the entertainment and climbed into bed, your mind could be racing for a couple of hours from the intense entertainment. 

Let's not place all the blame on Netflix (although it is a convenient proxy target for many modern sleep issues). 

Constant cell phone use - it's often the last thing people do before they go to bed and the first thing they check upon waking up - it's a major problem. 

Three out of 10 Americans are apparently almost constantly online

I have no idea what this picture's showing or who took the photo. Maybe his boss yelled at him. It appears to be someone escaping into a dark pod. Regardless, I want one: Sleep pod


Modern gizmos and their blue lights

Have you noticed most gizmos these days - WiFi routers, air purifiers, humidifiers, smart speaker, alarms - all have blue display lights? 

This is because blue conveys modern, high-tech, and fancy. 

Even dim light in your bedroom (as long as 10 Lux, which is equivalent to a city street at night) can cause poor cognitive function and memory the next day. 


What's the solution?

  • Dim down lights after sunset. 
  • Use smart lights like Philips Hue that can automatically remove blue from your home lights after sunset or say, after 8 PM.
  • Watch your shows earlier in the day.
  • Wear blue-blocking glasses after sunset. They need to be full wrap-around glasses that block light from the sides. There are prescription blue blockers now, but they are not all wrap-around to completely block blue light. Prescription blue-blockers that are not dorky-looking are as rare as hen's teeth. These UVEX OTG (Over the Glasses) are certainly dorky, but they fit over your prescription glasses. These UVEX Protege are hip and cool, but don't fit over your glasses. 
  • Using apps like f.lux can help block blue light from some laptops and devices. 

 (Late night eating is equally harmful, but we'll get into that in another article.)


 Avoiding light after sunset is only half way there

Avoiding bright light light after sunset is the ying to the yang of sun exposure during the day. 

You need both. Sunny days and dark evenings. 

So, what about sunny days? 

Before civilization gave us air-conditioned office jobs, most of us worked outside or spent a lot of time outdoors. Often starting our day with the sun. 

Our ancestors might have not known it, but they were living exactly the way our bodies were meant to. 

Bright daylight, rich in blues, decreases sleepiness and increases performance and vigilance. 

Now, we live in what I call Perma-Vegas, a state where, like the inside of a Vegas casino, days and nights are hard to distinguish. Our lives are illuminated by indoor lighting. This mostly indoor life is devoid of direct sunshine. 

That's OK for a day or two. 


Circadian Syndrome

If 'Perma-Vegas' sounds like an average day for you, you probably already have symptoms of something being called 'Circadian Syndrome.'

This used to be called Metabolic Syndrome but that name may be replaced with Circadian Syndrome because 'metabolic' suggests it's limited to just food and exercise. 

We now have proof that sunlight influences a LOT more than just sleep. We now know that our internal clock has a big effect on metabolic disorders and diseases. 

A strict 10 pm bedtime has been shown to reduce heart risk

This link to Circadian Syndrome takes you to the most fascinating paper I read during the 2020 pandemic lockdown. 

The paper identifies a cluster of features of modern living:

  • Light pollution
  • Controlled temperature
  • High food availability
  • Low physical activity
  • Stress
  • Jet lag (and social jet lag from staying up late on weekends)
  • Shift work

And the cluster of lifestyle factors above are strongly connected to:

  • Sleep disturbance
  • Insulin resistance
  • Depression
  • Obesity
  • High blood pressure
  • Fatty liver
  • Diabetes


Circadian Syndrome

Source: Zimmet et al. The Circadian Syndrome: is the Metabolic Syndrome and much more! Journal of Internal Medicine, 2019. 286: 181-191.


When people are exposed to bright light very early in the day, their melatonin production at night starts earlier and they drift off more easily into sleep when they get into bed. 

It also improved mental health.  


Just 5 to 10 minutes of sun exposure in the morning. Skip the shades. 

That's it.

Five minutes of exposing your eyes and face to the sun early in the morning does the trick. 

Don't wear shades or sun glasses - that defeats the purpose. But (obviously) don't look directly at the sun! 

Seratonin (often called the happy chemical), is what the body uses to make melatonin, and Seratonin is also influenced by sunlight

If you have an indoor job, get out in the sun a few times during the day (again, no shades!) and make sure you sleep in total darkness. 

There's a lot of chit chat about avoiding blue light. If you're a headline skimmer, you could easily come away thinking all blue light is bad. And there are several companies trying to sell you blue-blocking glasses for daytime use. This is a terrible, terrible idea. You NEED BLUE LIGHT DURING THE DAY!

Blue light during the day can help with mood, energy, and sleep quality. 


  1. Cut out light intensity after dark. If you really struggle with insomnia, go with candles. Try it for a month. 
  2. Wear blue-blocking glasses after sunset. 
  3. Get your TV show bingeing done earlier in the day. Here's a tip you never hear: just sit and be bored for a hour or two before bed. This may undo the effects of hyper-stimulating entertainment. 
  4. Get 5 to 10 minutes of sun exposure to your face and eyes in the morning, right after you wake up. If you live in a dark and cloudy part of the world, try this light box in the morning. 
  5. Get outside and get some sun a few times a day if you have a desk job. If your office is windowless, rethink your life. Get an office with a window. You're not a mushroom. Humans need sunlight. 
  6. Eat all your calories during sunlight hours. If you have severe insomnia, simply quit all calories after sunset. Yes, this requires some work and forethought about getting all your meals and nutrients condensed into an 8 to 10 hour window. If hunger is an issue, you are probably eating too many processed foods and not enough fiber and fat. 
  7. Keep your environment warm during the day and very cool at night. Keeping your environment at a constant 73 degrees can harm your sleep based on new research. A 10-15 degree difference between day and night helps. Otherwise, try to break a sweat once a day during daytime. Or if it's available, try a sauna. People I know who try saunas regularly claim it makes them sleep like a log - it's not supported by published science. Yet. 



Other tips:

Cognitive behavioral therapy.  

 Tim Ferriss discussing light and sleep with Dr. Andrew Huberman. This 3-minute podclip is absolutely worth your time - please give it a listen. 

New York Times with its usual mix of relevant and warmed-over, recycled health advice.  

Why Morning Light is so Crucial to Your Health - BBC Ideas

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