We evolved hunting and gathering food found exclusively in the outdoor environment. As such, we evolved to be outdoors in the Sun for much of the day. Therefore, the advice given by dermatologists to avoid the Sun runs contrary to the evolutionary evidence. New information about the human body's optical qualities is reshaping our stance against sunshine.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745411/

The Sun emits radiation across the electromagnetic spectrum, from high-energy X-rays to ultra-long-wavelength radio waves and everything in-between. Sunlight is described as full-spectrum light and includes the range of wavelengths necessary to sustain life on Earth: infrared, visible, and ultraviolet. The shorter wavelengths of infrared are known as near-infrared or NIR and represent 70% of the total amount of light we receive. 1 This post will concentrate on NIR.

Near-Infrared and Melatonin

NIR light penetrates deeply into our body, unlike UV and visible light. Evolutionarily, the human body has developed optical mechanisms to gather and localize NIR photons in the most sensitive areas of the human body: blood vessels, retina, brain, skin, and even the womb. 2 Research has demonstrated that NIR stimulates the production of antioxidants deep within our cells at the sub-cellular level. We use the reservoir of antioxidants to enhance the body's ability to contend with changing conditions throughout the day. Not surprisingly, the antioxidant produced is melatonin, as it has long been known as a potent antioxidant. The majority of melatonin found in our bodies, around 95%, is subcellular. Unlike circulatory melatonin, subcellular melatonin appears to be produced and stays primarily near the cell in which it is generated. This surprised researchers because melatonin has long been associated with the pineal gland and circadian rhythm.

Melatonin and the Circadian rhythm

A few posts ago, I mentioned the pineal gland that produces melatonin in the absence of light. Melatonin from the gland is released into our circulatory system. However, it only represents 5% of our total melatonin. The prime function of the melatonin produced by our pineal gland was once thought to act on our sleep-wake cycle. But the circulating melatonin also gets delivered to cells that need the additional antioxidant power during the night. The fact that nocturnal animals and night shift workers continue to produce high levels of circulatory melatonin during periods of high cellular activity appears to indicate melatonin's antioxidant properties are of primary importance. Specifically, circulatory melatonin is the "Hormone of Darkness," and subcellular melatonin is the "Hormone of Daylight." 3

Greenery Acts to Amplify NIR

Virtually all of our natural organic surroundings strongly scatter NIR photons. For example, the grass, clouds, and even dirt absorb visible photons and strongly reflect NIR photons. The photo above represents infrared scatter from the environment. As a result of the scatter, NIR penetrates deeply into our body to stimulate melatonin production and tissue repair, even into and through bone. 4 Conversely, UV, blue and visible light are absorbed on the surfaces of our skin. Blue light, which penetrates slightly deeper than UV, is also known as high energy visible light, or HEV, and it generates large amounts of free radicals in fat cells. Natural light, which includes NIR, will penetrate easily to the lipid layer simultaneously and stimulate melatonin production to undo the damage from the blue light.

The Human Body is an Optical System

Specifically, the scalp and skull block UV and Visible light but transmit NIR light into our cerebral spinal fluid that surrounds our brain, transmitting the photons deep within the brain's gray matter folds.

Similarly, amniotic fluid has a peak transmission of NIR light to the developing fetus. The Adolescent Brain Cognitive Development Study found that children spending more than 7 hours exposed to artificial visible only light sources exhibited thinning of their cerebral cortex. 5 Daylighting studies show increased learning rates under natural sunlight compared to artificial lighting. In all, the brain, retina, lens, cochlea, Harderian gland, airway epithelium, skin, gastrointestinal tract, liver, kidney, thyroid, pancreas, thymus, spleen, immune system cells, carotid body, reproductive tract, and arterial endothelial cells all have beneficial exposure to NIR.

Keszler et al. has shown that NIR photons stimulate the dilation of blood vessels based on absorption in the blood vessel walls leading to the release of nitric oxide-related compounds that lower blood pressure. Most of the capillary networks extending centimeters into the body are stimulated by NIR to release nitric oxide-related compounds, increasing blood flow and waste removal rates. 6

NIR Therapy and Dentistry

NIR treatments are also utilized in dentistry. The therapies are far from mainstream, however. The uses include treating painful sores from head and neck cancer treatments, treating pain from TMJ disorders, reducing postoperative pain and healing time from extractions, implant and periodontal surgery, and more.

Full Sunlight and Longevity

A 2016 study concluded that women with the most sun exposure during their lives lived longer, even though they had more cancer. They concluded that they had more cancer because they were living longer lives. They explained that the sun exposure produced less cardiovascular disease, and the result extended lives. Much of the benefits are due to NIR. Furthermore, they included data on smoking and concluded that sun-exposed women who smoked survived longer. 7

UV, Sunscreen, and Increasing Cancer Rates

For over three decades, skin cancer rates have continued to increase among Caucasians despite the development and widespread usage of UV-blocking sunscreen. However, under natural sunlight, the NIR photons have been shown to protect from the damage induced by both UV and visible photons in vivo. Sadly, from a dose standpoint, eight hours in the office generates the same number of free radicals as a half-hour laying out in the Sun.

Indoor Lighting Systems Are Lacking

Unfortunately, modern lighting lacks NIR light to counter the free radical formation from blue light. Many modern lighting systems contain only visible light. Also, many glass windows today don't let infrared light inside. We spend all day at the office bathed in visible light devoid of infrared and go home to the same situation. The result is we suppress melatonin production and inhibit good sleep. Over time, the lack of normal sunlight can lead to diseased states. Conversely, numerous studies have proven that subjects first exposed to NIR light before UV exposure protects the skin from damage equivalent to SPF 15. 8

Red and Near-Infrared Light Therapy

I have a red and NIR therapy unit at home. I use it for twenty minutes per day. The technical term for the treatment is photobiomodulation. Red light therapy increases blood flow, decreases damage from oxidation, decreases inflammation, increases energy, and boosts collagen production. The net effect of these benefits causes decreasing damage AND increasing repair to any tissue exposed to it. In addition, the lights are very safe to use and pose little to no risks. You can read much more about photobiomodulation in this post.

How To Increase Your NIR Exposure

Try to get bright sunlight exposure soon after waking.
Use a full spectrum lamp or a red/NIR therapy unit if you arise too early, the weather is bad, or too cold.
On very bright days, you need only minutes.
On cloudy days, you may need thirty minutes.
Don't wear sunglasses or stand behind glass, as it may block infrared.
Glasses and contacts are ok.
Blue light is beneficial during the day. You only need to avoid it after sunset.

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The Optics of the Body: How Sunlight Massively Boosts Total Body Antioxidants