All living beings - whether plants or animals - are nourished by light from the sun. While the mechanism by which we absorb and use sunlight differs, light allows all beings to live and thrive! 

Of course, you need no reminder that our modern lives have brought us increasingly indoors.

While modernity breeds convenience, it also means less time spent outside receiving the health benefits of natural sunlight, and more time inside under artificial light - largely out of sync with natural light/dark cycles. 

Today, let’s explore the different ways light affects us. With the resulting demand and subsequent rise in natural solutions for indoor light, it helps to understand the mechanism behind how all light works. After all, artificial light and sunlight do affect us in similar ways!

What is Natural Light?

It would be hard to get into a discussion of light and its effects on our health without first explaining what is natural light and what it’s composed of. 

Consisting of three main sections that fall along the electromagnetic spectrum, sunlight is composed of infrared light, visible light (the light used to see), and ultraviolet (UV) light.  

In order to understand how light affects us, it’s important to understand that all light - visible and other - has a wavelength and corresponding energy. As reflected above, as we move up the spectrum, wavelengths decrease and energy increases. 

The visible spectrum of light of course is no different: all colors comprising visible white light have their own energy and wavelength as well. 

As energetic beings, it shouldn’t be difficult to imagine the extent to which light and its corresponding energy influences us.

As you begin to read more on light and health, you’ll see the recurring mention of blue light. Referring to the bands of energy in the visible light spectrum occupying between around 380-500 nanometers, it’s this so-called “high energy visible light” that most profoundly affects us and our health! 

Biology and Light

So, how exactly does natural light, and high energy blue light affect us?

By dictating certain natural parts of our biology: light - and the absence of it - governs everything from our sleep/wake cycle to mood and hormones!

Circadian rhythm: how light affects a cascade of bodily functions

What is the circadian rhythm? 

If you’ve noticed that you tend to wake up, get hungry, and tired all around the same time - that’s your circadian rhythm, or your internal clock, at play! 

Controlling our body’s hormones, body temperature, and digestion (along with sleepiness and alertness!), the circadian rhythm is our body’s internal clock that cycles in response to the presence and absence of light in our environment. 

Every day, our circadian rhythm resets itself and goes through a new cycle of wakefulness, digestion, increased alertness, performance, and reaction time, blood pressure and body temperature fluctuations. All in perfectly-timed synchrony by the production and timed release of the hormones melatonin and  cortisol.

How does the circadian rhythm work? 

All in response to the presence and absence of light!

The key players in this response?  None other than high energy blue light, the retina of the eye and its non image forming photosensitive receptors, melanopsin (a light-sensitive retinal protein, contained within those intrinsically photosensitive receptors), and a portion of our brain’s hypothalamus, the Suprachiasmatic Nucleus (SCN). 

In simpler terms: when our eyes detect blue light, it triggers a signal to our brain, allowing the above cascade of effects (hormones, body temperature, alertness) to cycle through for one more cycle. In other words - another day has started!  

How does circadian rhythm affect health?

The simple presence of blue light stimulates our bodies and minds for the start of yet another day. 

Considering that everything in life and nature follows a cyclical pattern, we shouldn't be too different. 

Take a look at the following graphic: 

Remember how we mentioned natural light/dark cycles earlier? 

When it’s dark, the SCN signals for the production of melatonin, a sleep-inducing hormone. Over the course of the evening and night (starting at around 9 PM), melatonin supply steadily increases, reaching a peak somewhere around 2AM until it tapers off in the early morning (around 7:30AM) when the hormone cortisol (an energizing hormone) begins to rise in its place. Cortisol takes over and begins the process of rousing you out of sleep and into wakefulness and alertness for the coming day. 

But remember, the presence and absence of light are what keep this cycle moving efficiently.

Unfortunately, when it comes to light, our eyes can’t differentiate between natural light and artificial light coming from our light bulbs and other light sources (laptop screens, phones, etc.) 

By using bright lighting and our devices well into the night, our body won't signal for the secretion of melatonin, since it can't possibly be bedtime if the light is out!  

Over time, disruption to our circadian rhythms can affect more than just our mood, it can lead to a slew of health issues, such as diabetes, cardiovascular disease, and even cancer.

How to keep circadian rhythms in sync:

So, how do we make sure we keep our circadian rhythm in proper working order? 

Consider the following tips: 

-Shortly after waking in the morning, make it among your first priorities to get outside in sunlight, or turn on some bright, white lighting.

-Take the cue of the sun as it begins to set: start dimming your lights, and using high quality full spectrum incandescent light bulbs for the warmer, redder light containing minimal blue light.

-Install an app like f.lux on your computer to change your screen's color temperature, getting warmer as the night progresses. Dim screens as low as possible. 

-At least an hour before bed, ditch your devices altogether. (I don't know about you, but nothing beats the feeling of holding a real paperback in your hands!)

Light and our Mood: How the color and intensity of light affects our energy and mood

Now that we've been immersed into the world of light/dark cycles and our natural daily rhythms (and explored how to keep them running smoothly!), let’s explore how and why the color and intensity of light affects things. 

As we mentioned before, all light has corresponding energy and wavelength. We've gotten to know the high energy blue light responsible for stimulating our wakeful state, and we now know we need to reduce lighting as the evening progresses to induce production of melatonin and begin getting us tired. 

We've mentioned dimming light and using incandescent lights in the evening - but why is that?  

The color temperature of light throughout the day

Chances are, you're familiar with color temperature. And if you're not, you can read all about it here! Simply put, color temperature is the scale of warmth or coolness of visible light. 

In terms of sunlight, color temperature ranges between 5000K-6500K, and about 3000K during dusk and dawn. 

6500K is very white light, full of higher energy blue light. At the opposite end of the spectrum is red light, which as we know, will have a longer wavelength, and less energy than blue light.

During the course of one day, natural sunlight cycles through having varying amounts of blue light and red light. As the sun rises, light is golden, getting cooler and bluer at noon, until it gradually winds down as the day goes on, becoming warmer, redder, and less stimulating, until nighttime.

Remember the following guidelines:

Blue light is stimulating and energizing, increasing both alertness and productivity, while red light is soothing and relaxing. 

Artificial Light and Light Bulbs

Up until now, we've been talking mostly about natural sunlight; let's switch gears to discuss the light bulbs we use in our home. Now that we know how the real thing affects our biology and overall health, we should have a better idea of what to look for in terms of healthy light bulbs!

So, let's keep it simple: these are the health considerations to be aware of when choosing light bulbs.

Health Considerations of Light Bulbs:

Spectral Balance 

We haven't covered the fullness of spectrum in light, but suffice it to say: if you want a light bulb most similar to natural light, you don't want one with unnaturally peaking wavelengths! 

Blue Light + Timing of light 

Knowing what we now know about blue light, you'll want to limit your exposure to blue light in the evening and make sure to get enough during the morning and daytime. Doing so will keep your circadian rhythm in working order!  

EMF or electromagnetic frequencies

EMF stands for electro and magnetic fields or electromagnetic frequencies. While everything- including ourselves!- has electromagnetic fields, the increased amount of manufactured, modern-day signals has many in wellness circles concerned about the long-term effects of our continuous, around-the-clock, accumulated lifetime exposure to these frequencies. Some examples of EMF include cell phones, wifi, BlueTooth devices, and smart meters, to name a few. 

Flicker 

Search for the terms flicker and light bulbs, and the results are all about the visible flickering effect of a light bulb. When we say flicker, we mean the invisible flicker in all light bulbs - the rapid fluctuations in brightness that are too quick for us to visibly perceive. 

Even though flicker is invisible, it can still cause symptoms such as headaches, nausea, and eye strain, and all light bulbs have some amount of flicker - a mere byproduct of them being plugged into our AC electrical grid. 

While all light bulbs flicker due to changes in electrical current, the way incandescents "flicker" is more of a glowing effect from the filament's thermal inertia. An incandescent filament won't have time to cool off completely and turn off, while an LED responds instantly to variations in voltage, rapidly turning on and off. 

Parting Words

We hope this article has brought you some insight into the brilliant world of light and health! 

Considering how omnipresent light is in our lives, it's surprising how seldom it's spoken about - especially from a perspective of health and wellness! 

One point we didn't touch on is how light makes you feel. We always tell people, the healthiest light is the one in which you feel best.

Our motto has always been "see and feel better"; something to keep close to mind, in your quest for healthy lighting and beyond.

Thanks for reading and happy lighting!