Most life on our beautiful planet - plants, animals, and humans alike - is nourished by light from the sun. While the ways by which we absorb, use and even see sunlight differ, light allows most creatures to live and thrive! 

And, as humans, light is more than something that lets us see - it’s an essential part of our life and health!

As we’ll soon see, light “controls” our lives and overall health in many ways: It dictates not only our sleep-wake cycle, hormones, and other physiological systems in the body but can also greatly influence our mood, inspiration, and how we show up in the world. With so much on the line, it pays to know a thing or two about light! 

Today, let's take a deep dive into the different ways light affects our health. Whether from natural sunlight or light bulbs, our bodies interpret all light the same way -  so let’s do our best to understand it all! 

What is Light? 

Simply put, light is energy. Energy with a wavelength and frequency of oscillation. 

Consisting of three main spectrums that fall along a larger electromagnetic spectrum (which includes everything from gamma rays to radio waves), sunlight is composed of infrared light, visible light, and ultraviolet light.  Let’s explore! 

Understanding the full spectrum of sunlight: The three vital spectrums of light

Of these three light spectrums, only the small sliver of visible light oscillates in a frequency range that is observable by the human eye. While the other two spectrums of light are either too high a frequency (ultraviolet (UV) light) or too low a frequency (infrared (IR) light) to be detectable by the human eye, they are equally as important. The non-visible waves of infrared light comprise the majority of sunlight itself! 

While we won’t get too deep into the details of each spectrum, you can read our complete guide to the spectrums of light here. 

Ultraviolet (UV) light

Starting with the ultraviolet (UV) wavelengths, UVA, UVB, and UVC light are the invisible light wavelengths that comprise only about 3-5% of the total radiation from the sun. UVB is the light spectrum primarily responsible for the production of Vitamin D, and causes suntanning (and possible sunburn and damage from overexposure)! 

Visible light  

When most people refer to "light," they refer to visible light and the rainbow of colors that comprise it: Red, Orange, Yellow, Green, Blue, and Violet - all of which comprise white visible light that illuminates our surroundings and allows us to see.

As we’ll see soon, visible light and its constituent blue light wavelengths control the circadian rhythm: our internal clock that controls the sleep/wake schedule and other biological processes linked to the day/night diurnal cycle.

And you can’t discuss light and health without at some point hearing about blue light!

What is Blue Light? 

Perhaps the best-known (and most spoken about) of all the visible light wavelengths is blue light. Blue light is the shortest wavelength of visible light, which sits right above ultraviolet light. It is the first color wavelength of visible light right above ultraviolet. 

Blue light is present in high amounts in natural sunlight during the day and plays a critical role in human and plant life. The presence or absence of blue light controls our circadian rhythm and all the subsequent biological processes controlled by our 24-hour clock. We need high-quality blue light to regulate the body's circadian rhythm and improve alertness and mood. However, exposure to blue light, especially at night, can disrupt sleep and cause other health problems. 

Is blue light bad for you? 

The answer to whether blue light is bad for is: it depends! It depends mainly on the time of day (daytime / night time), the particular wavelengths of blue light, and whether that blue light is present in isolation or as part of a larger spectrum of light. To learn more, read this article to learn more about blue light.

What is Red Light

On the other end of the visible light spectrum are the red light wavelengths, the slower, longer wavelengths of visible light right before entering into the invisible infrared light territory. 

You may have heard of red light therapy or photobiomodulation - products emitting spectra in the red visible wavelgnths of light in addition to near infrared light,  a non-visible light spectrum we’ll cover shortly. Red light therapy is great for treating the skin, as well as suppling light energy to the mitochondria of our cells thanks to the longer wavelengths of these spectra and their ability to penetrate the skin and body. 

But before we learn more about infrared light, let’s continue on with the visible light spectrum and a very important aspect of visible light: color temperature.

Understanding the Color Temperature of Visible Light 

Color temperature is a measure of the "whiteness" of a light source. You’ve likely seen the verbiage “soft white/warm white” or “cool white” when out shopping for light bulbs - these words (along with the numerical Kelvin color temperature reading (3000K, 4500K, 6000K, etc.) are just indicators of how that light should appear when you turn it on: will the light be very yellow as in the case of a warm white bulb, or very white and blue, as in the case of cool white/ daylight white bulb?  

All this is helpful to understand from the lens of health and light: any light that is cool white/daylight white will an increased presence of blue light wavelengths, whereas warm white light will have less blue light. 

In terms of sunlight, color temperatures range between 5000K-6500K during the daytime, and about 2500K-3000K during dusk and dawn. 

Therefore, 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.

Warm Color Temperatures = Less Blue Light 

A so-called "warmer" color temperature light will have less blue light and more red light in its spectrum, appearing less blue/white and more amber/yellow/red. 

Cool Color Temperatures = More Blue Light 

Natural sunlight during the morning and daytime, for example, is what we'd call daylight white, with a full visible color spectrum, including high amounts of blue light wavelengths.

Infrared (IR) light

Segmented further into near (IR-A), mid (IR-B), and far (IR-C) infrared, the infrared wavelengths of light are non-visible wavelengths that have a longer wavelength than red visible light. Most sunlight energy is, in fact, infrared, with infrared light comprising 52-55% of sunlight!

Near-infrared light, in particular, is crucial for cellular health: IR light stimulates ATP production in the mitochondria of our cells, in turn increasing cellular energy production. We feel infrared light as the heat from the sun (or an incandescent light bulb!)

How does light affect health? 

Each of the above spectrums of sunlight is crucial for optimal health, controlling everything from our sleep/wake schedule, mood, hormones, our production of vitamin D, and cellular energy! 

The easiest way to envision how natural light affects our health is by segregating each effect into the spectrum of light needed to produce it. 

Here’s how each spectrum of light affects our health: 

• Visible light (and primarily blue light wavelengths) controls our circadian rhythm (sleep/wake cycle) and helps entrain us to our external environment.
• Ultraviolet light primarily helps the body to produce Vitamin D, but also helps with hormone production
• Infrared light helps with our overall cellular energy.

Of course, we need all three of these spectrums working in tandem for the greatest benefit to our health and wellness.  

We will spend the most time discussing visible light as it is the most crucial environmental cue for regulating our circadian rhythm, the all-encompassing internal clock that synchronizes with the diurnal day/night cycle and controls everything from sleep schedule to the secretion of hormones and metabolism and many other bodily functions. Keeping a consistent circadian rhythm is crucial for health and optimal wellness. 

Visible Light and the Circadian Rhythm

What is the circadian rhythm? 

Simply put, the circadian rhythm is your body's internal clock. 

If you've noticed that you tend to wake up, get hungry, and tired all around the same time each day - that's your circadian rhythm at play!

Responding to the presence and absence of light, the circadian rhythm synchronizes the body's functions with the 24-hour day-night cycle. It controls the timing of various physiological processes in our body, including hormone secretion, body temperature, and digestion (along with sleepiness and alertness!)  

Much of this is done by the secretion and control of two very important hormones for regulating our alertness during the daytime and sleepiness at night: cortisol and melatonin. 

Let's explore exactly how visible light controls this important circadian rhythm! 

How the circadian rhythm works 

The circadian rhythm is primarily controlled by the presence or absence of light, which acts as an input for a small region in the brain called the suprachiasmatic nucleus (SCN).

And, as we’ve been alluding, visible light, particularly some wavelengths of  blue light, play a crucial role in this process.

Blue light and the circadian rhythm 

The brain’s hypothalamus and SCN receive input from the retina, the light-sensitive layer of tissue at the back of the eye, through a specialized set of photoreceptor cells called Melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). 

While most photoreceptors (for example, the rods and cones,) relay visual-forming information to the brain,  Melanopsin-containing retinal ganglion cells are non-visual-forming cells, sensitive particularly to light in the blue spectrum. 

While all wavelengths of visible light will activate this signaling system and our circadian rhythm, our retinal ganglion cells and the photopigment melanopsin are primarily activated by shorter wavelengths of light, with peak absorption at around 480nm (blue light)! These wavelengths of light are present in high amounts in natural sunlight during the morning and daytime and in some artificial lights with a color temperature above 4000K.

When light is detected, the SCN sends a signal to suppress the production of the hormone melatonin, which promotes sleep, and instead stimulates the production of cortisol, which promotes wakefulness. 

This is why exposure to blue light in the morning can help to reset the body's clock and promote wakefulness, while exposure to blue light at night can disrupt the circadian rhythm and interfere with sleep. More on that later…

And remember, blue light wavelengths are the primary suppression signal for melatonin. If bright enough, any light (even red light) can suppress melatonin secretion!

Hormones Melatonin and Cortisol

Melatonin and cortisol are two hormones that release on opposing rhythms and are the primary chemical mediators providing the signals that set our internal clocks (among all their other roles!)

For this limited scope of discussion, melatonin initiates the inactive phase and increases our drive to sleep, while cortisol begins the active phase and increases alertness and wakefulness. And, as we saw, light exposure is the main environmental cue for releasing these two hormones. 

Melatonin

While melatonin has many other primarily protective, antioxidant functions in the human body, its best-known use is as the hormone that induces sleepiness. 

Produced in the brain's pineal gland, melatonin is typically released in response to darkness, with levels peaking at night and declining during the day. 

Ideally, melatonin rises at night, peaking around 2 - 3 am.

Cortisol

Cortisol, on the other hand, induces wakefulness and alertness. A steroid hormone produced and released by the adrenals, cortisol also controls metabolism and our bodies inflammation and stress responses, among many other processes, apart from its role in our sleep/wake cycle.

Peak level secretion of cortisol occurs between 7-8 am in the morning.  

The {ideal} reciprocal relationship between melatonin and cortisol

Melatonin and cortisol have a reciprocal relationship; when melatonin levels are high, cortisol levels are low, and vice versa. This makes sense: cortisol is an activating hormone meant to stimulate us during the day, while melatonin is overall a protective hormone. 

Ideally, melatonin should be released primarily at night, when we need to be asleep, while cortisol should be released primarily during the day when we need to be awake and alert. 

Exposure to bright light in the morning helps to suppress melatonin production and stimulate the release of cortisol, promoting alertness and wakefulness during the day. 

Exposure to dim or no light in the evening allows for an increase in melatonin production, which signals to the body that it is time to prepare for sleep.

Maintaining a regular sleep-wake schedule, getting exposure to natural light during the day, and limiting exposure to artificial light at night can help to promote a healthy circadian rhythm and ensure proper release of melatonin and cortisol throughout the day.

It’s also worth noting that - in the absence of light or any other environmental cues - circadaian rythms are endogenous processes. In other words, if you were in a dark cave with no electronics, you would fall asleep and wake up on a regular approximately 24 hour cycle, with the release of melatonin and cortisol occurring in their healthy, inverse relationship. 

But, that’s not the case for most of us. So As we’ve previously mentioned, keeping a consistent circadian rhythm is crucial for health and optimal wellness. 

Ultraviolet (UV) Light and our Health

UV Light and Vitamin D3 Production:

Perhaps most well-known fact regarding sunlight and our health (apart from the circadian rhythm of course!) is that sunlight and consitutient UVB radiation increase Vitamin D3 through a series of reactions 

As you likely know, Vitamin D is an essential vitamin that is pivotal in supporting immune function, ensuring robust bone health, and contributing to various physiological processes. 

Elevated Mood through UV Exposure:

Beyond its role in vitamin D synthesis, UV light has a discernible impact on our mood and well-being. Studies have established a connection between exposure to sunlight and a positive impact on mental well-being. Most of us perceive sun exposure as pleasurable - even stress-reducing -  associating it with an enhanced mood and improved energy levels.

A biochemical aspect adds depth to this phenomenon. The exposure of keratinocytes to UV radiation triggers the production of β-endorphin, an opioid. This β-endorphin, released into the bloodstream during UV exposure, may reach the brain in concentrations sufficient to induce mood enhancement and relaxation. It's a fascinating interplay between light, biochemistry, and our emotional state, highlighting the multifaceted benefits that UV light can offer beyond its role in vitamin D synthesis.

Infrared Light (IR) and Our Health 

In the world of wellness and holistic health, the potential benefits of Infrared (IR) light have become a subject of increasing interest. From reducing inflammation to enhancing skin health and even improving athletic performance, the impact of IR light on our well-being is both profound and fascinating. In this guide, we'll delve into the various ways in which IR light can positively influence our health.

Infrared Light Reduces Inflammation

At the heart of the infrared spectrum lies IR-A or Near-Infrared (NIR) radiation, a powerful force in Photobiomodulation. This process stimulates cellular activity and initiates healing within the body. The molecular dance orchestrated by NIR radiation, with a specific wavelength of 810 nm, involves the activation of a photoacceptor known as cytochrome c oxidase (CCO). This activation sets in motion a cascade of events that result in anti-inflammatory effects. The therapeutic potential of NIR light extends to conditions such as arthritis, tendonitis, and various inflammatory disorders, offering a natural and non-invasive approach to healing.

Infrared Light Improves Circulation

NIR light therapy goes beyond inflammation management, showcasing its ability to enhance circulation. By promoting the formation of new blood vessels and facilitating increased blood flow to damaged or injured areas, NIR light becomes a revitalizing force. This improved circulation not only aids in the healing process but also contributes to overall cardiovascular health. It's a gentle yet effective way to invigorate the body's natural pathways for optimal well-being.

Infrared Light for Improved Skin Health

For those seeking radiant and youthful skin, NIR light emerges as a powerful ally. Its impact on skin health is multifaceted, promoting collagen production and reducing the appearance of fine lines and wrinkles. Furthermore, NIR light plays a crucial role in wound healing by increasing the release of the growth factor and anti-inflammatory cytokine transforming growth factor-β1 (TGF-β1). This activation of fibroblasts sets the stage for improved wound healing, leaving the skin rejuvenated and revitalized.

Infrared Light for Pain Relief

NIR light has proven its efficacy in reducing both pain and inflammation. By triggering the release of endorphins and increasing blood flow to affected areas, it provides a natural and soothing remedy for various discomforts. Whether it's chronic pain, muscle soreness, or joint inflammation, the gentle warmth of NIR light offers a welcomed reprieve, addressing the root causes of discomfort.

Managing Light Exposure for Optimal Health

Well, that was a lot of information! 

How do we apply all this information about light to our day-to-day lives for a functional circadian rhythm and, ultimately, optimal health, wellness, and performance?  

Apart from getting adequate sunlight every day on bare skin (for Vitamin D, and mood enhancement), the simple answer is to time/control our light exposure!

You've likely heard you need to ditch the screens and blue lights at night. But let's go further!

Get bright white light every morning 

Morning/daytime = bright white light

Aim for at least 20 - 30 minutes of daylight exposure upon waking each day (without sunglasses for optimal exposure unless otherwise indicated by your medical provider/ophthalmologist). 

Remember, the presence of bright light signals to the brain to suppress the release of melatonin, while the absence of light will allow melatonin to rise. Getting plenty of sunlight (and constituent blue light) in the morning enables our master clock to "reset." 

Here are some tips to get your daily dose of bright white, stimulating light

- Open all window blinds + turn on overhead lights upon waking. Opt for light with color temperatures around 3750/4000K or above (natural white, cool white, or daylight white will work!) This R30 is our favorite for 4 or 5" recessed cans.  

- Get outside! Take a morning walk or have your morning coffee on the porch.

- Use a light therapy device to help on rainy days and during the winter. 

Turn off overhead lights and dim all sources of light in the Evening 

Night = Dim, Warm Light

Minimize or eliminate sources of light in the evening (device screens, overhead lights, etc.) Keep the brightness of all light at a minimum. Any light, if bright enough, can keep you up! 

Some tips to keep in mind for optimal release of melatonin

- Dim overhead lights or turn them off altogether. 

- Use desk and floor lamps outfitted with low wattage (i.e., dim) warm white light bulbs (our favorite is the Chromalux® 60W frosted bulb).

- If you'll be using devices, set screens to a warmer color temperature using an app like f.lux or your operating system display settings. Ideally, screens should be amber or red and very dim.

Understanding Light Bulbs and their Effect on Health

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.

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 

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. 

The importance of Real, Natural Sunlight 

While improving your artificial lighting (i.e., light bulbs) helps tremendously, always remember the best recipe fpr health is to get some of the real thing every day! Sunlight is not only life-enhancing; it is life-giving, and many processes, like the production of Vitamin D, are predicated on getting real sunlight daily. Also, remember that most light bulbs won’t ever substitute for the actual sun! Besides getting a tanning bed in your home, no full spectrum bulb can provide UV light. 

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 under which you feel your 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! 

Remember to choose your lighting like your life depends on it, because in many ways - it does! ;) 

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