Benefits of sunlight

Sunlight: A Powerful Health Tonic

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The concept of worshiping the sun is as old as civilization itself, with many ancient cultures celebrating the sun and sunlight by honoring gods named in honor of the giant ball of burning gas at the center of our solar system.

And for good reason, as the sun is essential for life. Solar energy was prized for its practical value in agriculture, lighting, and warmth before modern interventions made our environment more easily habitable.

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

Biologically, we benefit from sunlight to govern our circadian rhythms, create food, and synthesize biologically active compounds. Technologically, we can harness the sun’s energy to power our homes and businesses.

With so much time being spent indoors with our technological advancements, getting enough sunlight can be as worrisome as getting too much. This week’s blog breaks down the types of radiation emitted from 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

It takes 8.3 minutes for photons emitted from the sun to travel to Earth’s atmosphere.

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

Traveling at the speed of light, photons race toward us as waves of a variety of lengths, which have different energies and frequencies. Some of the shortest and most energetic waves are filtered out before they ever reach the Earth’s atmosphere.

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

Ultraviolet Light

Ultraviolet, or UV, light represents light of the shortest wavelengths that reach our atmosphere. It is often separated into three categories:

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

UV light, specifically 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 that it has greater potential to disrupt molecules and cells it touches, causing mutations in our DNA and damage to our cells and tissues (think sunburn and skin cancer).

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

Visible Light

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

Energy from light in this range drives the engine of photosynthesis, which is how plants transform sunlight into food for themselves, and ultimately for us. For this reason, visible light is also known as photosynthetically active radiation (PAR).

Though responsible for the colors of the rainbow and often considered harmless, visible light contains energy that has the potential for damaging our cells.

High energy visible (HEV) light, of wavelengths measuring about 400-450 nm, can create free radicals that cause oxidative stress. Also known as blue light, HEV occurs in abundance from the sun, but also from screens and LED lights. Overexposure to blue light, particularly from artificial sources that emit wavelengths of light from a narrow range rather than a broad spectrum, may have harmful effects, particularly affecting 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 700 nm to 1 mm, sometimes separated into three categories – infrared A, B, and C.

These lower frequency waves can penetrate through clothing and beyond the skin cells to deeper tissues, effectively warming the body on a chilly, yet sunny day, but also triggering important cellular functions.

Near infrared radiation (NIR) ranges from approximately 650-1200 nm and comprises up to 70% of the sun’s rays, depending on the angle of the sun. NIR, encompassing part of the red portion of the visible spectrum and 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 reduce blood pressure.

Furthermore, new research proposes that photons of this wavelength trigger the production of melatonin at the cellular level. Though this melatonin doesn’t circulate in the blood, it is produced at much higher concentrations than the pineal gland produces at night.

Turns out melatonin is a daytime hormone too.

Melatonin: Not Just the Hormone of Darkness

When I wrote about the importance of melatonin for sleep, I was under the assumption that melatonin was exclusively produced by the pineal gland at night. And I suppose that is the case for circulatory 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 as mitochondria, which are organelles inside a cell that generate ATP (energy) primarily from glucose and oxygen, generate a large quantity of reactive oxygen species as they operate.

As an effective antioxidant, melatonin helps to protect this energy-deriving machinery from oxidative damage by neutralizing free radicals on its own, while also promoting the production of other powerful antioxidants like glutathione.

To recap, blue light, or rather the absence of blue light triggers the pineal gland to produce melatonin that circulates through the body while we sleep. Red and infrared light triggers the production of cellular melatonin during the day.

Similar to plants’ ability to absorb wavelengths corresponding to both blue and red in order to balance energy intake in times of low and high light intensity, respectively, our bodies have multiple pathways to ensure an adequate supply of a precious substance: melatonin. As is true in holistic philosophy, using the whole spectrum of light yields optimum results.

How to Practice Safe Sun

As the days grow longer and warmer, summer beckons us to be outside. Here are some practical tips to make the most of solar energy, without getting burned.

Consider the time of day

Altitude, latitude, seasons, clouds, and time of day influence the degree of solar irradiance, meaning that the composition of the sun’s rays varies.

Low solar angles (such as at dawn or dusk), higher latitudes, lower elevation, and cloud cover represent scenarios that decrease the intensity of the sun’s energy.

Energy from the sun is more intense during midday, at higher elevations, and in certain parts of the Northern Hemisphere during the summer months.

Woman Enjoying a Sunset on the Beach

Taking in the sun earlier and later in the day helps to increase exposure to lower-energy NIR wavelengths while decreasing exposure to high-energy UV and HEV wavelengths. Campfires, candlelight, and incandescent bulbs also provide a great source of NIR photons, so you can benefit from light and heat even while the sun is on the other side of the planet.

If being in direct sunlight during peak sun hours is unavoidable – about 10 am to 4 pm – consider other protective measures, such as the following.

Cover up

Cellular damage, such as sunburn, occurs during prolonged exposure to UV rays. These highly energetic light waves don’t penetrate through clothing and can’t hurt you while you’re 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 sunlight even while in the shade! Infrared light is reflected off surfaces like clouds, trees, buildings, and the ground, making it possible for your body to absorb its warmth and stimulate antioxidant production to protect your cells from byproducts of energy production and higher-energy sunlight.


As holistic nutrition practitioners, we take great care to consider which ingredients are safe and effective to put in or on your body. A great sunscreen will protect against a broad spectrum of sunlight (UV-A and UV-B are most important) and won’t contain any controversial ingredients that harm us or the environment. Avoid sunscreens with a sun protection factor (SPF) of greater than 50, as higher SPF offers negligible protection and exposure to more concentrated chemicals is greater. Check out this previous NTI blog for a more detailed description of sunscreen considerations.

While important for prolonged exposure to the sun, sunscreen is not a “get out of jail free card”. Even the best sunscreens don’t protect you against all forms of highly energetic sunlight, like HEV light.

Stay Hydrated

Fun in the sun often goes hand in hand with a little extra perspiration. Be sure to drink plenty of water and consume foods with high water content, including fresh fruits and vegetables like watermelon and cucumbers.

Get Outside!

Humans evolved to be outside with the elements. As time marches on, we are spending more time inside with artificial lights, and less time outdoors reaping the benefits of a broad spectrum of light energy. Rejoice in the power of the sun – the giant, brilliant source of energy that powers our lives in so many ways.

Related reading…

Vitamin D: The Sunshine Prohormone

Making the Most of Vitamin D During the Summer Months

About the author: Karyn Lane is a recent graduate of NTI’s Nutrition Therapist Master 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. You can follow her on Instagram @karyn.aka.klaryn.

About Nutrition Therapy Institute’s Holistic Nutrition Certification

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

Images: Image by Birol Bali from Pixabay; Image by Jill Wellington from Pixabay

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