Does Sunlight provide Red Light Therapy? Health Benefits of the Sun Explained.
Life on this planet has relied primarily on sunlight as a life-sustaining source of energy. Originally, humans perceived the only contribution of sunlight to our health was through the food chain. However, over the past centuries it has become clear that sunlight is a useful therapeutic modality for many conditions, and recent decades of research has found the many "light therapies" offered from different parts of the sunlight spectrum.
Thus out-springing many new sciences and therapies called Red Light Therapy, Low Level Laser Therapy (LLLT), Photobiomodulation, Bright Light Therapy, UV therapy, NIR Heat Lamp Therapy, Infrared Sauna Therapy, and even other colors of visible light for therapies.
This science and industry has mostly embraced newer technologies like LEDs, Lasers, Incandescent, fluorescent, and other artificial light bulbs to deliver this new therapy.
However, is there any evidence that says sunlight is a source of light therapy? How come we don’t see any clinical studies in this field using sunlight?
Specifically speaking, the method of using Sunlight for therapy is called Heliotherapy. With the root word “Helio-” literally meaning sun and derived from the Greek god Helios who was a personification of the sun.
While most companies don’t want you to get free therapy from the sun, in fact some companies are desperately try to claim to “patent” thier red lights or make them seem proprietary, we finally take an evidenced-based look at the benefits of sunlight and how it compares to Red Light Therapy panels.
Wavelengths and Intensity of the Sun
Most experts will agree that red light therapy depends on two main parameters, wavelength and intensity. As long as the wavelengths are generally between 600nm to 900nm, it shouldn’t matter what kind of light source it is – LED, Laser, Incandescent, or Sun.
A photon is a photon after all, and your body generally can’t discern a difference between sources.
So what is the spectrum and intensity of the sun? A reliable measurement comes from ASTM as the solar reference spectrum that they have measured and make available publicly.
In it, we can easily calculate that sunlight emits 34.8 mW/cm^2 of light in the 600nm to 900nm range. That is 34% of the overall solar spectrum in the Red to Near-Infrared therapeutic range!
Certainly that is sufficient intensity and power because we know most red light panels emit between 7 to 50 mW/cm^2 at the recommended treatment distance (despite most of them false-advertising and saying it is over 100mW/cm^2).
Sunlight is generally 100mW/cm^2 across all the wavelengths!
Note that this is the ONLY appropriate usage for a Solar Power Meter. As the name implies, they are calibrated for the broad spectrum of the sun, and will read falsely high when measuring Red and NIR LED lights.
In one study the authors even acknowledge this intensity from the sun, and express their concerns that sunlight exposure during clinical trials could mess up the dosing calculations. And too much sunlight, plus their photobiomodulation protocol, could lead to an unwanted biphasic dose response. 
Even clinical researchers can easily acknoledge the overlap between sunlight exposure and photobiomodulation dosing.
UV Light and Health
When searching for the effects of sunlight on human health on Pubmed, we are flooded with results of UV light. Since UV light, the shortest wavelength of the light spectrum (below 400nm), has the highest frequency – it seems to have the highest bioactive response.
Of course, the main measurable contribution of UV light to health is the production of Vitamin D. Which we know Vitamin D is a critical hormone for the immune system, bone health, hormone balance, and much more.
Along with the benefits of UV light, many studies also caution against too much Sun exposure due to risk of sunburn, eye damage, and skin cancers.
Unfortunately the mainstream medical establishment tries to make people afraid of sunlight for these reasons and prevent us from enjoying the vast benefits of sunlight we will be reviewing. But we know that taking practical and sensible precautions with sun exposure is key to enjoy all the benefits that the sun has to offer.
One peer-reviewed article does attempt to shift the focus away from the benefits of sunlight merely as a Vitamin D producer, and that the science of Photobiomodulation is teaching us many more benefits from the spectrum of the sun namely from Red and Near-Infrared light. 
So we are finding more and more examples in the research that scientists and authors are understanding the benefits of Red and NIR contained in sunlight.
Photobiomodulation Wavelength Range
This might surprise some people, but the science called Photobiomodulation includes a wide range of colors and light wavelengths, not just Red and Near-Infrared. People often confuse that Red and NIR light are the ONLY wavelengths for Photobiomodulation.
In fact, a recent article co-authored by Dr. Hamblin the first sentence is:
“Photobiomodulation (PBM) therapy refers to the non-thermal use of visible to near-infrared light (400 to 1100nm) to stimulate many biological processes.” 
So this means that violet, blue, teal, cyan, green, yellow, red, NIR, and FIR can all be considered as Photobiomoduation. It just happens that Red and NIR are the most interesting to study for their superior penetration, wide range of benefits, and safety profile. Hence the confusion and why most studies are focusing on the Red to NIR range.
Other Beneficial Wavelengths:
Naturally, the sun also provides full-spectrum light with all of these wavelengths and colors. So lets take a look at the potential therapeutic benefits from a couple of other wavelengths.
Blue Light: Blue light is the shortest wavelength after violet, so it still carries with it some antibacterial and antiviral activity similar to UV. Blue light is often used for acne and skin conditions, but too much can cause skin and eye damage. 
Infrared Light: Longer wavelength Infrared light is preferentially absorbed by water in our skin. This leads to a heating effect from the inside, making for efficient heat therapies and applications in far-infrared sauna. Benefits range from cardiovascular health, sweating and detox, athletic recovery, and circulation improvements. 
Heliotherapy and Sunlight Therapy Studies:
Now all this math and theory about proper wavelengths and intensity is good, but are there any studies that ACTUALLY use sunlight as a therapy?
Like most companies using pseudoscience to claim their red light panels offer clinical benefits – yet their actual devices were never clinically studied and are vastly different than the devices used in the studies they reference. We like to apply some rigorous science to verify our observations and theories.
So lets take a look at some real Heliotherapy studies and see what benefits or results they are seeking and finding.
- Heliotherapy started in the 18th century as a tuberculosis treatment. https://pubmed.ncbi.nlm.nih.gov/29465107/
- Spanish Flu and Pandemic Influenza have been treated with sunlight in the 1918 outbreak and was successful in reducing symptoms, spread, and morbidity. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7194064/
- Sunlight used in babies to treat acute bilirubin encephalopathy and hyperbilirubinemia. https://pubmed.ncbi.nlm.nih.gov/34228352/
- Daily sunbaths for children was recommended to protect from tuberculosis and rickets. https://pubmed.ncbi.nlm.nih.gov/32966597/
- Dematologists have recommended Sunlight as a natural home-treatment for Psoriasis. https://pubmed.ncbi.nlm.nih.gov/33811728/
- Studies used Heliotherapy in Psoriasis and Atopic Dermatitis.
- Filtered Sunlight used as a treatment for neonatal jaundice. https://pubmed.ncbi.nlm.nih.gov/28919246/
- Other skin disorders treated with Sunlight such as psoriasis and pityriasis rosea. https://pubmed.ncbi.nlm.nih.gov/9472434/
- Sunlight exposure correlated with improved recovery from a recent trending respiratory illness. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184988/
- Sunlight therapy has been used for depression and improved mood. https://pubmed.ncbi.nlm.nih.
Some epidemiological studies investigate the long-term effects of adequate sunlight exposure and health.
- Correlation between sunlight in Mediterranean countries and less cardiovascular mortality. https://pubmed.ncbi.nlm.nih.gov/18704704/
- Correlation between sunlight exposure and less stroke risk. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3563869/
- Sunlight exposure was correlated with less osteoporosis in a Korean study. https://pubmed.ncbi.nlm.nih.gov/34164956/
- A survey of sun exposure showed a correlation between sun exposure and less hypertension. https://pubmed.ncbi.nlm.nih.gov/33721253/
Many of these studies verify our expectations that sunlight offers a wide range of benefits both in short-term respiratory diseases and several skin disorders. As well long-term benefits of sunlight are correlated with bone health and development, cardiovascular health, and less stroke.
Abandoned Sunlight for Artificial Light?
Starting in the 1920’s, sunlight usage for respiratory illnesses and childhood treatments were abandoned for artificial lights. And of course, starting in the 1960’s came Low Level Laser Therapy, the precursor for Photobiomodulation. Which predominantly uses Lasers and now LEDs. 
The Western medicine establishment rarely recognizes "natural" treatments such as sunlight as a viable therapeutic tool. We prefer artificial devices to feel like we have control.
Researchers seem to prefer fancy new “technologies” for medical treatments versus the natural alternatives. As well artificial lights offer more control over the wavelengths and intensity administered, allowing us to understand the effects under better clinical circumstances.
So while there is certainly many possibilities for using sunlight as a clinical therapy, the mainstream interest especially in the Western medicine is towards using artificial technology. Which explains the apparent lack of studies with Heliotherapy.
Sunlight Deficiency Diseases and Mortality:
We talked about the benefits and therapies with sunlight, but what happens when we are deficient in sunlight exposure? That is to say, we are deficient in exposure to wavelengths and intensity of sunlight, Vitamin D deficient, and Bright Light deficient.
One study says that 50% of the world’s population is at risk of being deficient in Vitamin D. Which causes issues in childhood development, and puts people at risk for cancer, weakened immune systems, bone health issues, and cardiovascular disease.  
Another study claims that insufficient sunlight exposure is responsible for 340,000 deaths per year in the United States alone. It is related to all-cause mortality, cancer, cardiovascular disease, Alzheimer’s disease, metabolic syndrome (diabetes and obesity), Multiple Sclerosis, and respiratory disease. 
Of course, low Vitamin D status is correlated with higher risks of catching and severe outcomes in a recent trending respiratory illness. 
And some studies find that incarceration (jail) is associated with increased metabolic disorder and cardiovascular issues – acknowledging that lack of sunlight plays a role. 
It is clear that sunlight should be regarded as an “essential nutrient” of health. Deficiency in sunlight, with a clear health marker as Vitamin D levels, leads to dire consequences including many modern diseases.
Sunlight Versus Red Light Therapy Panels:
Now that we have established the wavelengths, intensity, benefits, and deficiencies around sunlight. What are the real positives and negatives if we are trying to compare Sunlight to the regular Red Light Panel.
Pros of Sunlight:
- Full-Body Coverage
- 34% in Red to NIR range (600nm-900nm)
- UV and Vitamin D benefits
- Benefits of blue & FIR light (and other colors)
- Bright Light Therapy benefits
- No Flicker or nnEMF
Cons of Sunlight:
- Modesty might restrict being fully naked outdoors
- Lack of outdoor access or immobility for some people
- Weather, Climate, Latitude, and Time of Day dependent
- Sunburn risks will limit exposure time
- Skin Cancer risks with excessive UV exposure
- Hard to “control” the exposure for clinical trials
- Skin reflection of light reduces penetration
- UV and Blue light associated with eye damage and aging 
Pros of LED Red Light Panels:
- Specific Wavelengths Emitted
- Known Intensity Emitted (if the company offers 3rd party data)
- Used indoors in comfort and privacy
- Can multitask indoors (potentially)
- Can use any time of day
- No UV damage
- Extremely safe wavelengths
- Better penetration when using skin contact
Cons of LED Red Light Panels:
- Expensive for a Full-Body setup
- Can be bulky and take up space
- Risk of nnEMF and Flicker exposure
- Some companies not accurately marketing intensity
- Skin reflection losses if used >6 inches away
- No Vitamin D production (no UV)
Sunlight offers massive benefits over Red Light Panels, but too much sunlight is associated with sunburns, skin cancer, eye damage, and aging. Where Red Light Panels primarily offer more convenience and are much safer since they only emit Red and NIR light.
We are finding that humans and animals evolved in specific ways that our bodies can utilize the wavelengths from the sun in many different ways that affect our biology. Sunlight has historically been used to treat respiratory illnesses and certain skin conditions, and it is clear that regular sun exposure is correlated with less morbidity and less age-related chronic diseases.
Sunlight certainly delivers the correct wavelengths and intensity that is equivalent to most red light panels on the market. We know sunlight also delivers many other beneficial wavelengths as well including UV which helps us produce Vitamin D.
As long as we are mindful of sunburn limitations to exposure, sunlight is a fantastic health-promoting delivery method for Photobiomodulation and other light therapy benefits. Sunrise and sunset are ideal times of day to get Red and Near-Infrared light from the sun because UV is being blocked and scattered by the atmosphere at those times. One study recommends that if your shadow is taller than you are, then you are getting the ideal sun exposure to Red and NIR and safely avoiding UV. 
Notice that sunlight at sunrise and sunset appears to be more orange or reddish! That is when it is ideal to enjoy Red and NIR light for free from the sun.
Getting outside in the sun might not be possible for everyone who might be bedridden or have a busy indoor lifestyle. Or some people are in latitudes or climates that limits direct sunlight for several months at a time. Red Light Panels offer a convenient alternative to allow us to “supplement” some benefits of sunlight in the privacy of our own home or office. And higher-powered lasers and LEDs held in skin contact may offer better penetration than sunlight for hard-to-reach issues.
So while there are many positive reasons to use red light panels, it is important to resist the hype and get the holistic benefits from the Sun as much as possible. If given the option, we go outside in the sun over using a red light panel.
Thanks for reading! If you enjoyed this article, you may also enjoy our article on the Best Time of Day to do Red Light Therapy!
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