Sunlight: A Powerful Health Tonic


The concept of sun worship is as old as civilization itself. Many ancient cultures celebrate the sun and sunlight by honoring gods named in honor of the vast sphere of burning gas at the center of our solar system.

And with good reason, because the sun is essential to life. Solar energy was valued for its practical value in agriculture, lighting and heating before modern intervention made our environment more livable.

Although civilization has advanced, the glory of the sun cannot be denied.


Biologically, we benefit from sunlight to regulate our circadian rhythm, manufacture food, and synthesize biologically active compounds. Technologically, we can use the sun’s energy to power our homes and businesses.

Since we spend so much time indoors with our technological advances, getting enough sunlight can be just as worrying as too much. This week’s blog breaks down the types of radiation emitted by the sun and their effects, how near-infrared radiation affects melatonin secretion, and practical ways to safely get enough sun exposure (but not too much!).

types of solar radiation

Photons emitted by the sun take 8.3 minutes to enter Earth’s atmosphere.

Photons are units of electromagnetic radiation, which includes light and electricity. They have energy and motion but no mass or electrical charge. Light behaves as both a particle and a wave, a concept that shares light with matter called wave-particle duality.

Photons travel at the speed of light, rushing towards us as waves of different lengths with different energies and frequencies. Some of the shortest and most energetic waves are filtered out before they even reach Earth’s atmosphere.


The following list represents types of solar radiation that reach Earth from the shortest to the longest wavelengths and how they are used for the benefit of our planet and its inhabitants.

Ultraviolet light

Ultraviolet or UV light is the shortest wavelength of light that reaches our atmosphere. It is often divided into three categories:

  • UVA (315-400nm)
  • UVB (280-315nm)
  • UVC (100-280nm)

Ultraviolet light, particularly UVB, is the type of solar radiation responsible for converting 7-dehydrocholesterol (a metabolite of cholesterol) on your skin into the prohormone vitamin D.


However, UV light is also a mutagen. Its short wavelength and high frequency make this type of light highly energetic. More energy means it has a greater potential to destroy molecules and cells it touches, causing mutations in our DNA and damage to our cells and tissues (think sunburn and skin cancer).

Fortunately, this type of light cannot penetrate through clothing or further into the body than skin cells or the retina. Fortunately, skin cells are quickly replaced and the retina contains many filters to mitigate the damage from these energetic rays.

visible light

Visible light corresponds to wavelengths that the human eye can discern, approximately 380 nm to 750 nm, with the shortest wavelengths in this range appearing purple and the longest appearing red.


Light energy in this range powers the engine of photosynthesis, allowing plants to convert sunlight into food for themselves and ultimately for us. For this reason, visible light is also referred to as photosynthetically active radiation (PAR).

Although visible light is responsible for the colors of the rainbow and is often considered harmless, it contains energy that has the potential to damage our cells.

See also  The Maillard Reaction: Why Food Tastes So Good

High-energy visible (HEV) light with wavelengths around 400–450 nm can generate free radicals that cause oxidative stress. Also known as blue light, HEV comes in abundance from the sun, but also from screens and LED lights. Excessive exposure to blue light, particularly from artificial sources that emit light wavelengths from a narrow range rather than a broad spectrum, can have harmful effects, particularly on the eyes and sleep patterns.

infrared light

Finally, beyond the visible color red, come longer wavelengths of solar radiation known as infrared light, or radiant heat. Infrared light occurs at approximately 700nm to 1mm and is sometimes divided into three categories – Infrared A, B and C.

These low-frequency waves can penetrate through clothing and beyond skin cells to deeper tissues, effectively heating the body on a cool but sunny day, but also triggering important cellular functions.

Near-infrared (NIR) radiation ranges from about 650-1200 nm and accounts for up to 70% of the sun’s rays, depending on solar radiation. NIR, which includes part of the red portion of the visible spectrum and is sometimes referred to as red light therapy, has been shown to dilate blood vessels by triggering the release of nitric oxide-like compounds that increase blood flow and lower blood pressure.

In addition, new research suggests that photons of this wavelength trigger the production of melatonin at the cellular level. Although this melatonin does not circulate in the blood, it is produced in much higher concentrations than the pineal gland produces at night.

It turns out that melatonin is also a daytime hormone.

Melatonin: Not just the hormone of darkness

When I wrote about the importance of melatonin for sleep, I assumed that melatonin is only produced by the pineal gland at night. And I assume this is the case with circulating melatonin.

Melatonin is produced locally in the mitochondria of many cells, from the vascular endothelium to the brain, skin, reproductive system and even a growing fetus. This makes sense because mitochondria, which are organelles within a cell that produce ATP (energy) primarily from glucose and oxygen, produce a large amount of reactive oxygen species during their operation.

As a potent antioxidant, melatonin helps protect this energy-yielding machinery from oxidative damage by itself neutralizing free radicals while promoting the production of other powerful antioxidants like glutathione.

To recap, blue light, or rather the lack of blue light, triggers the pineal gland to produce melatonin, which circulates throughout the body during sleep. Red and infrared light triggers the production of cellular melatonin during the day.

Similar to plants’ ability to absorb wavelengths that correspond to both blue and red to balance energy intake during times of low and high light intensity, respectively, our bodies have multiple pathways to ensure adequate supplies of a valuable substance: melatonin. As is the case in the holistic philosophy, the use of the entire light spectrum leads to optimal results.

How to practice Safe Sun

As the days get longer and warmer, summer lures us outside. Here are some handy tips to get the most out of the sun’s energy without burning yourself.

Consider the time of day

Elevation, latitude, seasons, cloudiness and time of day affect the amount of solar radiation, which varies the composition of the sun’s rays.

Low sun angles (eg, at dawn or dusk), higher latitudes, lower elevations, and cloud cover present scenarios that reduce solar energy intensity.

The sun’s energy is more intense during midday, at higher elevations, and in certain parts of the northern hemisphere during the summer months.

Woman enjoys a sunset on the beach

Sunbathing earlier and later in the day helps increase exposure to lower-energy NIR wavelengths while decreasing exposure to high-energy UV and HEV wavelengths. Campfires, candlelight, and incandescent lamps are also great sources of NIR photons, allowing you to benefit from light and warmth even when the sun is on the other side of the planet.

See also  Why is Drinking Water Important and How Much Water Should You Drink?

If it is unavoidable that you will be in direct sunlight during the peak hours of the sun – say between 10 a.m. and 4 p.m. – you should consider other protective measures such as the following.

Cover up

Cell damage such as sunburn occurs with prolonged exposure to UV rays. These high-energy light waves do not penetrate clothing and cannot harm you in the shade. Hats, long-sleeved clothing, or umbrellas are great ways to avoid exposure to the most damaging forms of sunlight during the heat of the day.

In addition, you can still benefit from the sunlight even in the shade! Infrared light reflects off surfaces such as clouds, trees, buildings and the ground, allowing your body to absorb its heat and stimulate antioxidant production to protect your cells from energy production byproducts and more energetic sunlight.


As holistic nutrition practitioners, we take great care to examine what ingredients are safe and effective to put in or on your body. A good sunscreen protects against a broad spectrum of sunlight (UV-A and UV-B are most important) and does not contain controversial ingredients that harm us or the environment. Avoid sunscreens with a sun protection factor (SPF) greater than 50, as a higher SPF provides negligible protection and there is greater exposure to more concentrated chemicals. See this previous NTI blog for a more detailed description of sunscreen considerations.

While sunscreen is important for prolonged sun exposure, it’s not a “prison-free card.” Even the best sunscreen doesn’t protect you from all forms of high-energy sunlight, like HEV light.

drink enough

Fun in the sun often goes hand in hand with a little more sweat. Be sure to drink plenty of water and eat foods high in water, including fresh fruits and vegetables like watermelon and cucumber.

Go out!

Humans evolved to be out with the elements. Over time, we spend more time indoors with artificial light and less time outdoors to take advantage of a broad spectrum of light energy. Enjoy the power of the sun – the gigantic, radiant source of energy that fuels our lives in so many ways.


About the author: Karyn Lane is a recent graduate of NTI’s Nutritional Therapist Masters program. She finds her chemistry degree a useful tool in her study of holistic nutrition. She also loves to treat her kitchen as a laboratory for new recipes and cooking techniques. Follow her on Instagram @karyn.aka.klaryn.

About the Nutrition Therapy Institute’s Holistic Nutrition Certification

The Nutrition Therapy Institute (NTI) is a leader in holistic nutrition education. Since 1999, NTI has provided its students with the highest quality nutrition training by offering comprehensive holistic nutrition courses. Offering online and in-person nutrition course options to help students achieve successful careers as holistic nutrition therapists. Interested in starting our holistic nutrition courses and earning your holistic nutrition certification? Join an informational webinar to learn more by registering HERE.


picture of Birol Bali out Pixabay

picture of Jill Wellington out Pixabay


Leave a Reply

Your email address will not be published.