Light is all around us. It allows us to see (and gives objects their color), warms our bodies, and produces electricity through solar panels. Sunlight is considered a requirement for living a healthy, happy life.  We communicate and entertain ourselves through transmissions that are encoded on light-absorbing sensors and then displayed elsewhere in the world on arrays of light-emitting diodes.

In other words, light is a huge part of the human experience -- both naturally and technologically. But what is light, really? And what else can it do for us? The science behind light runs deep, but we can discuss the fundamentals without having to open up any quantum physics textbooks (phew!).

First, let’s understand what comprises light. Light is an electromagnetic wave, just like radio signals, microwaves, x-rays, or gamma rays. All of these things, including visible light, exist on the same spectrum. 

Light is made up of photons, the fundamental particle of light and the smallest discrete amount of electromagnetic radiation. Photons are not particles in the same sense as elementary particles like protons and electrons.

Electromagnetic waves that are  classified as light are those with wavelengths between 400nm to 700nm.  These wavelengthscan further be broken down into to individual colors of visible light.   The individual colors become visible when white light passes through a prism, or when sunlight passes through raindrops, creating a rainbow. These colors are located in the small part of the spectrum 

WHAT CAN LIGHT DO FOR US?

Light is constantly helping us whether we notice it or not.

The sense of sight stems from receptors in our eyes that turn visible spectrum photons into nerve impulses in our brains. Infrared (IR) light from the sun keeps the earth warm. Ultraviolet (UV) light is absorbed by our skin and synthesized into vitamin D.

Medical researchers have, over the past few decades, been exploring other ways that light can help us. After all, we’ve proven that our body chemistry reacts to UV light in life-changing ways, so what benefits, if any, are offered by other types of light? The results of such experiments, studies, and tests have been eye-opening to say the least. We are now on the verge of truly understanding just how powerful light can be from a health and wellness standpoint.

BIOACTIVE LIGHT

Our bodies need certain types of light at certain times to be healthy. The negative effects we’re subject to from an absence of light are well-documented. Seasonal affective disorder (SAD) is caused by diminished natural lighting in winter, while rickets results from  a vitamin D deficiency caused by too little time in the sunlight.

Clearly, light can affect us and our state of being. When we talk about light that causes changes in the human body, we’re talking about bioactive light.

Our understanding of light’s effects on the body has grown immensely over the past decade. The importance of bioactive light is well known, and more people are becoming aware of how different types of light can affect their health and wellness.

There are actually several types of bioactive light that can bring about changes in our bodies (for better or for worse):

• Blue light helps to set and regulate our internal clocks.
• UV light allows us to synthesize vitamin D from sunlight.
• Far Infrared light heats up our bodies and helps with circulation.
• Red and Near Infrared lights stimulate cellular energy production.

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

Our bodies evolved to make use of certain types of light in various ways. Changes in our behavior and modern technology are both responsible for causing imbalances in how much light we’re receiving and when. This in turn can cause any number of negative effects.

Let’s take a closer look at the role played by each type of light and how they contribute to a healthier, happier life:

UV LIGHT AND THE BODY

At the far end of the electromagnetic spectrum is a wavelength of light that’s too short for us to see called ultraviolet (UV) light or ultraviolet radiation. The short frequency of UV rays means that they vibrate quickly, giving them a higher level of energy than visible light rays. This is why exposure to UV light can cause sunburns and eye damage, while exposure to a plain incandescent light bulb will not.  While overexposure to UV light can be damaging, in the proper doses it helps our bodies synthesize the vitamin D we need to maintain healthy bones. It also strengthens muscles and the immune system.

UV light is also used in the treatment of certain skin conditions. Once such condition, psoriasis, causes the skin to shed cells too quickly and results in itchy, scaly patches. Exposure to UV slows the growth of the skin cells and helps to relieve the symptoms.

Other research suggests that sunlight plays a key role in maintaining a healthy disposition. UV light stimulates the brain’s pineal gland, causing it to produce a mood-enhancing chemical called tryptamine.

BLUE LIGHT AND HEALTH

Right beside UV light on the spectrum, we find blue light. About one-third of all visible light is considered high-energy visible (HEV) or “blue.”

Blue light has a short wavelength with a high energy signature, which scatters more easily than other visible light. Computer screens, smartphones, and other digital devices that emit significant amounts of blue light can cause eye strain because of the high amount of unfocused, scattered light that they emit. Sunlight is also a source of blue light.

Blue wavelengths are beneficial during daylight hours because they boost attention, reaction times, and mood but become disruptive at night. This can throw off our circadian rhythms and cause significant sleep disruption as exposure to blue light has been shown to reduce melatonin production significantly during sleep.

Studies have linked  modern health issues, including  diabetes and obesity,  to increasing levels of blue light from technology and LED lighting.

RED/INFRARED LIGHT

With wavelengths from 400nm-1000nmwe find visible red light and  invisible infrared (IR) light.

IR light is the heat you feel from sunlight and radiating from a hot sidewalk. Your skin naturally radiates infrared heat as a byproduct of biological functioning.

In contrast with UV light, which has been found to be damaging at high levels,  infrared light has been shown to help cells regenerate or repair themselves. Infrared light can also improve blood circulation, which has been shown to promote faster healing and reduced symptoms of chronic pain.

Infrared light is able to penetrate below the skin layers, also unlike UV light which is stopped from penetrating the body by outer layers of skin. The deep-penetrating nature of IR light provides a much greater depth for therapeutic use. Since it is typically able to reach 2 to 7 centimeters deep into the body, infrared light reaches the muscles, nerves, and even the bones. 

Once inside the body, infrared light is absorbed by the photoreceptors in cells. The light energy sets off a series of metabolic events, triggering several natural cellular processes. [Can we provide examples?]

It is thought that infrared light may have so many positive effects on the body because of its relationship to nitric oxide production. Nitric oxide, a gas that’s vital to the health of the circulatory system, is a cellular signaling molecule that helps relax the arteries, battle free radicals to reduce oxidative stress, prevent clotting in the vessels, and regulate blood pressure. In doing so, this molecule enhances circulation to deliver vital nutrients and oxygen-rich blood to damaged tissues in the body. This stimulates the regeneration and repair at injury sites, reducing pain and inflammation.

https://www.healthline.com/health-news/red-light-therapy-benefits

www.aimspress.com/article/10.3934/biophy.2017.3.337/fulltext.html

https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.201600176