Is It Time to Welcome Back NIR?

By Scott Zimmerman and Deborah Burnett

In addition to the three requirements necessary to sustain life - food, water and air - human beings are designed to be dependent upon continuous exposure to a Complete Biological Spectrum (CBS)* of natural daylight and evening darkness abundant with near-infrared light (NIR). Throughout our evolution, humans have been exposed to biologically relevant protocols of combined UV, Vis and NIR spectral distributions governed by the location of the solar orb above and below the horizon line. The ever-changing spectral distributions are a cohesive energy source conveyed as a continuum of bioactive stimuli upon which various skin, eye, and neuronal receptors are activated throughout the body and brain producing two types of melatonin. By their very nature, select CBS bandwidths are a source of eustress (good stress) which elicit various epigenetic stress responses necessary for our survival and assimilation to the Earthly location we presently occupy. Interestingly, the responses are strategically aligned with the location of the solar orb above and below the horizon line to activate in a coordinated series of 24/7 neuroendocrine, biochemical, and physiological responses each designed to maintain and reinforce brain homeostasis and its anticipatory response for adapting to environmental changes. These include the circadian primary zeitgebers of dynamic CBS, daylight-to-dark ambient temperature fluctuations, and individual habits of preferential feeding times which either support or disrupt digestive tract function and normal processing.

*Complete Biological Spectrum (CBS): A high cohesive biologic stimulant comprised of electromagnetic bandwidths composed of UVA, UVB, VIS and NIR wavelengths currently known to elicit a human biologic response

The electromagnetic spectrum, in order of increasing wavelength.

The Sun: Primary Provider Of Energy And Driver Of Biology

The most basic survival trait of any organism is two-fold; conserve energy and adapt quickly to environmental changes which will impact survival within that environment. The primary source of energy on Earth is the sun, and all terrestrial living beings are dependent upon that energy. Successful adaptation requires anticipation; thus the human brain, body, and biology are evolutionarily designed to function in a state of homeostatic anticipation as to awareness of the position of the solar orb and to successfully respond in advance of the transition between light and dark. Current scientific understanding is still scratching the surface for an accurate assessment of the exact model as to how the sun and our biology work together. But, NIR is making investigators take a second look at this bandwidth, as it is proposed that the NIR portion of natural sunlight stimulates an excess of antioxidants in each of our healthy cells and that the cumulative effect of this antioxidant reservoir is to enhance the body’s ability to rapidly and locally deal with changing conditions throughout the day.

Melatonin: Biologically Connecting Sleep at Night and Activity During the Day

For humans, achieving quality sleep at night is a two-step biological process beginning with exposure to UVA and NIR early in the morning so that that the act of sleep can happen at night. This is identified as the homeostatic sleep process (HSP) and is supported by two types of melatonin, both of which are dependent upon the sun and its position above and below the horizon line. As a component of total solar energy, near-infrared (NIR ) is instrumental for supplying the cellular and metabolic energies needed for optimized continuation of the HSP and the circadian rhythm throughout our lifespan. Melatonin in both of its forms plays a critical role by working synergistically with both. The most recognized form of melatonin is an endocrine hormone expressed from the pineal gland directly into the circulatory system for the purpose of downstream epigenetic and sleep-related neuroendocrine responses. Primarily known for its role in sleep initiation and maintenance, pineal melatonin is also a vital player in its role as a tumor suppressant via regulatory protein P53, which also plays a role in stem cell development and the regulation of the cell cycle, apoptosis, and genomic stability. It is estimated that the pineal gland accounts for less than 5% of the total melatonin produced in mammals. (4)

Circadian rhythm is 24.2 hours on average and must be synched to Earth's L/D photoperiod of 24 hours. Circadian rhythm amplitude is robust in morning ensuring arousal and mid day alertness and then decreases throughout the day through premidnight hours. Sleep need or pressure is low upon awakening and increase throughout the day then plummets sharply prior to midnight for most adults. Adenosine, a vital nucleoside occurs in all cells and is derived from adenosine triphosphate (ATP) which is the primarv energy source of the cells. It increases throughout the day upon activity and exposure to bright daylight rich with high energy blue wavelengths. It drops off at night @ 10PM and will begin anew with the onset of the cortisol awakening response (CAR) which for adults begins between 4-6 AM.

The second form of endogenous melatonin, extrapineal melatonin, is produced in the mitochondria found in virtually all our cells. This distributed reservoir provides local and rapid response to everyday activities including ATP production exposed to NIR. Because of its distributed transient nature, extrapineal melatonin is measured in our body fluids during stressors (exercise, NIR whole body treatments, sex, eating, etc.), unlike pineal melatonin, which is measured under sedentary conditions. As shown below, during intense exercise, plasma melatonin concentrations rapidly increase in the blood stream and then plateau for the remainder of the exercise. Once the exercise stops, melatonin levels slowly return to the circadian baseline. Sweat and plasma melatonin measurements during a wide range of exercises support that extrapineal melatonin increases during the day in sunlight. (2) Adenosine, a nucleoside derived from adenosine triphosphate (ATP), is a primary building block of RNA and DNA. It is the primary energy currency throughout the body and is produced continuously throughout daylight hours starting with the Cortical Awakening Response (CAR). It increases throughout the daylight hours and into the early night during physical activity and exposure to NIR and possibly moonlight. Unlike visible electromagnetic radiation, NIR penetrates the skin, underlying tissues, and organs; thus it can directly impact the physiology of these cells. Most lighting pros falsely assume that the CCT of moonlight is a cool 4125K even though the SPD demonstrates a robust majority presence of long wavelengths including NIR.

CREDIT: Scott Zimmerman

Credit: James Benya and Deborah Burnett

Emerging research is now also demonstrating that darkness-expressed pineal gland melatonin has uniquely evolved to protect and enable the brain to operate at 80% capacity during periods of low cellular activity (sleep). It is also speculated that the remaining reservoir of extrapineal melatonin necessary for production of alertness-promoter adenosine will be available to serve until adenosine suppression naturally occurs, usually around 10:00 p.m. in most latitudes. This ensures that the remaining extrapineal melatonin will provide the extra energy needed by the circulating pineal melatonin to remain vigilant while the brain is in a reduce energy state. This is a critical concept to grasp, as the two purposes extrapineal melatonin serves at this time juncture are critical for providing the brain a safe opportunity to reduce its energy needs and rest in order to prepare for higher energy demands the following day. The stimulus for triggering these actions is the location of the solar orb either above or below the horizon line. Our speculation is that the position and phase of the moon will also play a role in supplying the NIR stimulus for extrapineal energy production to assist the pineal gland as a secondary source of energy for the necessary tumor suppressant functions needed at night during the brains low energy capacity while we sleep.

Here's how it works: the early morning hours, prior to the solar rise up from 18 °below the horizon, are a particularly stressful time for the immune system. It is here where the most opportunistic tumors expand in size and metastasize. Unfortunately, this is exactly when the energy stores of pineal melatonin are beginning to deplete in advance of the Cortisol Awakening Response a few hours later. Extrapineal melatonin is available to supplement the depleting pineal melatonin, p53 and the adaptive immune system, to interfere and/or prevent with tumor growth and expansion beyond its primary site while the sun is below 18°. The period between 2 a.m. and 4 a.m., when circulating pineal melatonin and the organs it influences are in a low energy state, is when extrapineal melatonin provides the additional energy for the pineal melatonin tumor suppressant p53 to remain vigilant. While pineal melatonin may be the “Hormone of Darkness”, subcellular melatonin may be considered the “Hormone of Daylight." (1)

Cortical Awakening Response: Waking Up Biology Before You Wake Up

If you start at midnight, the pineal gland is secreting melatonin into the CSF to allow the brain to operate at 80% of daytime levels and provide supplemental melatonin to all our cells during a period of low cellular activity. Melatonin was uniquely selected for the job because of its antioxidant prowess. The brain anticipates the coming day and in the early morning hours starts to elevate cortisol levels. As light impinges on the skin and through the eyelids, cortisol continues to rise. As our cells wakeup and ATP kicks in, extrapineal melatonin starts to rise. NIR further stimulates extrapineal melatonin along with other stressors (eating, exercise, etc.) Outdoor NIR is always in excess to visible light. Melatonin suppresses cortisol, providing a necessary counterbalance to extra adrenal cortisol generated in the skin triggered by melanopsin in the skin and retina. Around noon, melatonin to cortisol levels hit a minimum, generating maximum alertness. As the afternoon progresses, NIR increases faster than Vis, and a nap seems like a good idea under the shade tree. Throughout the day, both cortisol and extrapineal melatonin increase in unison to naturally occurring stressors. Under natural stressors, the body is designed to generate an excess of melatonin. Like pushing on a sponge soaked with water, stressors can cause the release of excess melatonin into our body fluids and blood stream. Time lag generates an excess of melatonin immediately following a stressor; this is why we feel tired after strenuous activity.

CREDIT: Terry Craille

This transient fluctuation rides on top of the circadian baselines which are measured under sedentary, no food, no exercise conditions. Essentially, we have been measuring only a small portion of the body’s hormone response to real life. For 600,000 years we gathered around a campfire (NIR) that further increased extrapineal melatonin, and the brain induces the pineal gland to secrete melatonin, starting the cycle all over again. The development of real-time wearable biosensors is for the first time revealing how our hormones are responding to both circadian and non-circadian events, and it is the summation of both that determines our health. (3)

Adenosine also plays a role in the CAR. While melatonin is the primary hormone for our internal body clock, adenosine serves as a quantitative sleep indicator. While adenosine builds up as we consume energy, the act of sleeping serves to break down adenosine, resetting our bodies in preparation for the next day. Reducing adenosine while sleeping is a critical factor for maintaining the continual system of energy production and the alignment with the circadian rhythm. Sleep deprivation fails to give our body enough time to break up adenosine, which may, in turn, lead to an adenosine build-up over time. It is this failure of adenosine breakdown that leads us to feel groggy when we wake up.

Time to Return NIR? … or Begin Active Investigation

For almost twenty years, the LED lighting industry's awareness of bioactive spectra for both circadian support and sleep has evolved to embrace a Full Spectrum Lighting (FSL) light source devoid of NIR. This has evolved primarily focusing on visible wavelengths for circadian alignment. Continuning to promote the singular model of Vis only wavelengths intending to artificially support both the circadian process and elicit efficacious sleep at night fails to understand the synergistic nature of each process and how both are dependent upon NIR. With increasing scientific interest in melatonin and NIR, maybe IT IS time for the lighting industry to work together to investigate the potential for light sources combining both VIS and NIR. ■

References

1. Tan, Dun-Xian, Melatonin: both a messenger of darkness and participant in the cellular actions of non-visible solar radiation of near infrared light. Biology 2023, 12(1), 89; https://doi.org/10.3390/biology12010089

2. Zimmerman, S.; Reiter, R.J. Transient responses of melatonin to stress. Melatonin Res. 2022, 5, 295–303.

3. Torrente-Rodríguez R.M. Investigation of cortisol dynamics in human sweat using a graphene-based wireless mHealth system. Matter. 2020 Apr 1;2(4):921-937. doi: 10.1016/j.matt.2020.01.021. Epub 2020 Feb 26

4. Zhao D., Yu Y., Shen Y., Liu Q., Zhao Z., Sharma R., Reiter R.J. Melatonin synthesis and function: Evolutionary history in animals and plants. Front. Endocrinol. 2019; 10:249. doi: 10.3389/fendo.2019.00249