Light as Medicine: the body clock’s incredible time-keeper

“Wear sunglasses.”

“Cover up when you go outside.”

“Put on sunblock”

Good health advice? Absolutely not!

In fact, that’s awful advice, most of the time..

I decided to write this series because most people are TOTALLY in the dark (understandably) on the subject of light, and suffering tremendously as a result. 

This series is going to challenge many of common beliefs about the effects of light on the human body. You’ll learn why sunlight is crucial to your overall wellbeing and how detrimental artificial light can be if not used wisely.

Artificial light can:

• ruin your circadian rhythm

• disrupt hormone production

• alter the function of your energy production machinery (mitochondria)

• change your sleep, hunger, energy use, fat storage and sets you up for disease
  
  

However, when used correctly, the right kinds of light can actually heal tissues we are told are ‘unfixable’, including your skin and eyes!

Essentially, what is boils down to is this:

Sunlight = 

• an incredibly potent signal for our bodies at a molecular (and consequently systemic) level!

• initiates many important cellular processes  

• is a master regulator of circadian rhythm (which controls everything)
  
  

Artificial light (when used incorrectly) =

• damaging to tissues

• ages us prematurely

• induces stress signals

• disrupts our circadian rhythms (hormones, sleep, digestion, mood, energy)

Surprising, right?

Prepare to have your MIND BLOWN by how much humans actually need on sunlight, yet we are taught we need to avoid it, blocking these benefits and inviting disease. 

So please, put on your blue light-blocking glasses, turn off those bright LED lights, turn down your screen brightness, and let’s dive in. 

LIGHT & A RESTFUL NIGHT

Light has a profound effect on sleep: exposure to light early in the day stimulates the body and mind, encouraging feelings of wakefulness, alertness, and energy. Light exposure at night also stimulates alertness, challenging sleep and reducing sleep quality. Similarly, insufficient darkness throughout the night can lead to frequent and prolonged awakenings.

Light – our daily ‘pacemaker’

Sunlight is good for your circadian rhythm and makes it easier for the body to release chemicals that prevent wakefulness and help you fall asleep. On the other hand, spending time indoors sends a confusing message to the brain. Artificial lights at night (especially LED and fluorescent) have been proven over and over to keep us awake by delaying sleep onset.

For most of history, humans had no need to seek out darkness. Nightfall would signal our ancestors’ bodies to wind down for the night, sending the body into sleep mode by triggering a cascade of biochemical signals in the body. 

The advent of electricity in the 20th century, however, fundamentally changed our relationship to light and sleep, and poses serious new health challenges.

Adding to this, the widespread use of digital technology - especially blue light emitted from screens and LEDs - has introduced another layer of challenge for our bodies.

We now know that “excessive” (ie. today’s average) exposure to blue light is harmful to our health: researchers have found these high energy light waves strain our eyes and can cause long-term damage to the retina and neurodegeneration in photoreceptor cells. This leads to to macular degeneration and blindness in all experimental organisms that have similar eyes as humans… Yikes!

Many studies also now link exposure to blue light at night with obesity, diabetes and heart disease: in people whose circadian rhythms are consistently disrupted (as in shift workers or so-called “night owls”), blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down.

…It’s even linked to certain types of cancer, including colorectal, breast, thyroid and others. 

In fact, we are so attuned to light that any wavelength of visible light at the wrong time of day disrupts our “circadian rhythms”, the natural biological cycles of signals in our body that tell us when to sleep, wake, eat, etc.

Even very dim light at night (over 5 lumen) messes with our sleep and circadian rhythms! (What’s a lumen? A standard 40-watt bulb delivers about 450 lumens of light, so it’s very, very little….your alarm clock LED screen, charging devices or a streetlight outside your window probably top that.) 

Why? Well, not only are there photoreceptors in our eyes, but our skin is light-sensitive too! Cool, huh? What’s more, new research shows artificial light disrupts the skin’s stem cell renewal cycles (also on a circadian clock), which may represent a novel factor in aging.  (See PART 2 for more on this.)

Bottom line: we now have a HUGE body of evidence on the disruptive nature of artificial light on the human body from solid studies in credible, peer-reviewed journals, and have even been issued (quiet) warnings from government regulatory bodies…and yet, most people are completely unaware that artificial light wreaks havoc on our bodies. I might on a bit of a crusade to change that…

Every creature has a circadian rhythm. (From latin: “circa = about + dies = day.) Light is one of its key influences.

The mechanisms that control these clocks are extraordinarily complex, but suffice to say there is a group of genes - literally called the “clock genes” - that indirectly respond to environmental cues like light. We’ve known for over 30 years that light exposure at the wrong times of day disrupts the body's internal 24-hour "clock", or “circadian rhythm.”

This is a problem because our circadian rhythms not only regulate sleep-wake cycles (4), but many other essential body processes you might not think are linked to light as well. These include digestion, insulin signalling and fat storage, stress levels, brain repair, memory formation, stem cell renewal (ie. bodily rejuvenation), your microbiome, and more. 

(Fun fact: when you have jetlag, you have “circadian dysrhythmia.”)

How darkness influences sleep

Darkness is essential for good, healthy sleep: the absence of light sends a crucial signal to the body that it is time to rest, while light at the wrong times interferes with both the quantity and quality of sleep. 

Here’s a little science on why light exposure at the right times is SO important:

Melatonin, the "sleep hormone", accumulates during darkness - specifically, in the absence of blue light. 

It sends a signal to the brain that it is time for rest and initiates the body's physiology for sleep — muscles begin to relax, drowsiness increases, body temperature drops and metabolism downshifts. 

Melatonin levels naturally rise during the early evening as darkness falls, continuing to rise through most of the night before peaking at ~3am. 

Melatonin then decreases during the early morning and drops sharply in response to sunlight, remains low during much of the day. 

When we disrupt this cycle, not only do we disrupt melatonin, but we disturb the fine balance with all of the other hormones, neurotransmitters and pathways that cycle in concert with it (right). 

Clearly, the whole human system is incredibly intricate in this way: a change in one signal has a domino effect on a whole bunch of other things. This is why it breaks down after a while if we don’t tend to it properly.

Light can affects not just when you can sleep but how well you sleep.

1. If you’re exposed to bright light (especially blue wavelengths) before bedtime, then your brain will still be wide awake (see PART 2 to understand why). This means that it will take you a longer time to transition from the wakeful stage to the first stage of sleep, light sleep.
   
   

2. It can also disrupt the quality of your sleep by changing your “sleep architecture.” AKA - Redistribution of the amount of time spent in each of the 4 stages of sleep (light, deep, REM, waking). This means that you can wake up feeling groggy or unrested, even if you have seemingly had a full night’s sleep.
   
   
   

Practical tips for preserving melatonin  

My clients often suffer with fatigue or sleep problems.

They sometimes say they’re ‘night owls’ or that they “can’t go to bed early.” 10pm seems atrocious! 

I then ask them, 

“What do you do right before bed?” 

Almost inevitably, they answer:

“Check my phone.”
”Watch a show.”
”Catch up on email/facebook/etc.”

I reply:

“That’s why you “can’t sleep” - all that blue light at night is sabotaging your sleep.”

What NOT to do.

My top 5 rules for healthy hormones & fixing derailed circadian rhythms:

1. Stop using screens 2 hours before bed.

2. If you must use a screen within 2 hours of bedtime, always dim screens AND use orange-tinted blue light-blocking glasses* (see below).

3. Sleep with blackout curtains, an eye mask or shawl over your eyes.

4. Make sure you don’t have a bunch of LEDs shining on you while you sleep. (Use electrical tape over charging ports, alarm clocks, etc.)

5. Don’t wake up and stare at your screen first thing. Allow natural, gentle light to wake you, not intense, artificial blue light.

Blue-blocking glasses usually make an incredible difference. My clients almost always report feeling far more relaxed and experience less eyestrain, fewer headaches and less fatigue when they wear them too.  (They’re usually shocked at this difference this one change makes to their sleep and general sense of calm!)

I also suggest that my clients install blue-light filtering software like IrisTech on all their devices to protect the health of their eyes, as blue light is now known to damage eyesight over time. ($15 for a lifetime subscription, and you can totally customize the way your screen looks.)

All this said, despite glasses or blue filters, any bright light from screens or otherwise will still disrupt your sleep and hormones. Really, all light entering your eyes must be very dim or preferably a red hue to allow melatonin to properly accumulate. Think candles, sunset, fire light or red light bulbs. (I use these in my room.)

Ideally, of course we wouldn’t spend nearly as much time on screens…but such is the modern way, and so we must adopt modern habits to accommodate the blue-light sensitive, ancestral forms we live in… until we figure out a better, kinder sort of screen. Or bionic eyes. 

In the future, I suspect we will look back on these damaging screens and bright white LEDs and wonder how we tolerated them…

*On blue blocking glasses:

I like BluBox: they’re great quality, stylish, made by a great company run by lovely people, and they work… (NOTE: This is NOT the case for some of cheap ones you find on Amazon - many don’t do a great job of light filtering and are a waste of your money.)

I use a clear pair during the day (left) and an orange-tinted pair at night (above right). They make a world of difference! Now, I won’t use screens for any significant duration with out them.

Further reading:

https://pubmed.ncbi.nlm.nih.gov/30311830/

https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side

https://www.webmd.com/eye-health/blue-light-health#1