Near Infra Red (NIR) Light and Health - A Big Deal

Today, I’m diving into a fascinating article by Scott Zimmerman and Russel J. Reiter, titled Melatonin and the Optics of the Human Body, published in Melatonin Research (2019). This piece flips the script on what we thought we knew about melatonin, light, and how our bodies interact with the sun’s rays. It’s a game-changer, especially for how we think about kids’ health in our modern, screen-filled indoor living world.

First, what is melatonin? Melatonin is a hormone made from the essential amino acid, tryptophan. It was first isolated from a cow's pineal gland. It is an old molecule as primitive bacteria made melatonin probably 2.5 billion years ago. Its synthesis in bacteria and eukaryotes is a common linkage. Most of us know that melatonin is the “sleep hormone,” produced by the pineal gland in the brain when it gets dark at night, signaling to our bodies that it’s time to wind down and prepare to sleep. It’s the chemical expression of darkness, driving our circadian rhythms and helping us catch those precious brain cleansing moments. Zimmerman and Reiter argue that this is only half the story or maybe even less than half. For decades, research has hyper-focused on pineal melatonin that is regulated by visible light hitting our retinas. Blue visible spectrum light in the early morning suppresses pineal melatonin, which is why we should dim those screens before bed. But here’s where it gets interesting, the pineal gland isn’t the only place melatonin is made, and darkness isn’t its only trigger. Our bodies are producing melatonin in ways we’re just starting to understand, and it’s tied to light in a way that was unexpected and evolutionarily fascinating. As with all things in science and evolution, we learn what we did not know and it all makes sense once the aha moment occurs.

The newly discovered melatonin is the subcellular type produced in the mitochondria of nearly every cell in our bodies. Unlike pineal melatonin, which follows a circadian rhythm and gets released into the bloodstream, this subcellular melatonin stays local, acting like an on-demand antioxidant to mop up free radicals (those pesky molecules that damage cells, especially DNA). This is a fascinating discovery for those of us avidly following the melatonin story as we wrongly believed in the Pineal melatonin finality with sleep as the final common pathway.

Now the question has to be answered, what drives sub cellular melatonin production in order to meet these antioxidant needs? Near-infrared (NIR) light, the invisible part of sunlight that makes up over 70% of the solar spectrum, stimulates this subcellular melatonin production. So, sunlight, particularly NIR, is boosting melatonin in all of our cells during the day. So, while pineal serum melatonin is the “hormone of darkness,” subcellular melatonin could be the “hormone of daylight.” How’s that for a new science twist?

Now, let’s talk about light and optics, because this is where Zimmerman, an optics expert, really shines. Sunlight isn’t just the visible stuff we see, red, blue, green, etc.... It’s a broad spectrum, from ultraviolet (UV) to NIR, wavelengths stretching from 250 nm to over 4000 nm. Blue light (400-700 nm) gets all the attention because it messes with our sleep by suppressing pineal melatonin, but it’s only about 2% of sunlight’s output and barely penetrates our skin. NIR, on the other hand, is a long wavelngth that is the heavyweight, penetrating inches into our bodies through clothing, muscle, brain, even bone. It’s like a biological Wi-Fi signal, collected and distributed through our cerebrospinal fluid, blood vessels, and other tissues, reaching nearly every cell. This is especially true in kids whose smaller bodies let NIR hit up to 100% of their cells.

Think about that reality. The sun, a constant for humans, has been adapted to as a source of oxidant reduction for all of our cells. This is a huge revelation for cellular biology and aging in general. NIR penetrates deep inducing biological reactions that are anti inflammatory everywhere energy is burned to make ATP, i.e. cellular respiration.

This deep penetration is why NIR is the star of newer therapies for inflammation reduction like infrared saunas and hand help IR devices for autoimmune conditions and neuropathic pain.

Evolution is amazing! Mammals evolved to use near infrared waves to supercharge our cells’ antioxidant defenses, cellular protection against the oxygen radicals released during cellular oxygen based metabolism - movement, thinking, infection fighting and so forth. When NIR hits our mitochondria, it triggers melatonin production, creating a reservoir of antioxidants ready to tackle free radicals throughout the day. This is huge because free radicals are constantly generated by normal metabolism, stress, or environmental toxins. The authors propose that our bodies evolved expecting regular NIR exposure from the sun, moon, or even firelight, all of which are rich in NIR. This constant NIR bath kept our cellular melatonin levels high, helping us adapt to daily stresses and repair damage on the fly. In kids, whose cells are still developing, this NIR-driven melatonin production might be even more critical for growth and resilience. Children are at risk for cellular damage if the oxidant load is high which happens with poor quality food intake, chemical exposure, acute and chronic stress and more.

But here’s the real problem, our lifestyle choices in our modern world is NIR-starved. Incandescent bulbs, which we used for over a century, gave off 90% of their energy as NIR, unintentionally mimicking sunlight’s benefits. Today’s LEDs? They’re visible-light-only, with zero to almost zero NIR. Add to that low-emissivity glass that blocks NIR and our obsession with staying indoors (hello, screen time!), and we’ve created a “perfect storm” of NIR deficiency. Kids are especially vulnerable because their developing brains and eyes need NIR to support healthy growth. Studies show that natural sunlight exposure reduces myopia risk and boosts academic performance. ( NIR’s bio-optical effects and the act of looking at the distant horizon keeping the eyes focal point variable which holds eye shape centric and prevents oblong induced myopia). Yet, we slather on sunscreen, park kids in front of screens, and wonder why chronic diseases are spiking. We need to sound the alarm that our lighting choices and indoor lifestyles are starving our cells of the NIR they evolved to expect.

I encourage a full read of the article to see the connection and understanding of how our bodies are optical marvels, designed to collect and distribute NIR like a high-tech fiber-optic network. Cerebrospinal fluid acts as a light guide, channeling NIR deep into the brain. The skin, eyes, and even the womb amplify NIR’s effects, ensuring it reaches the fetus and young kids’ developing tissues. The lighting and medical communities need to team up to rethink how we design our homes, schools, and offices. We’ve spent billions on circadian lighting based on pineal melatonin, but ignoring NIR and subcellular melatonin is like treating half the patient.

The takeaway: Get your kids outside, folks! Sunlight isn’t just about vitamin D, it’s about bathing all of our cells in NIR to boost melatonin and keep their antioxidant defenses humming. I’m not saying ditch the sunscreen entirely, but let’s balance sun safety with sun exposure. Ditch the LED-only bulbs where you can, and consider lighting that mimics the sun’s full spectrum. And let’s rethink screen time, not just for blue light’s sake but because it’s keeping kids indoors, away from NIR’s benefits. Our bodies evolved under the sun, and our kids’ health depends on us reconnecting with that natural rhythm.

Dr. M

Waisberg Nature

Zimmerman Melatonin Res

Tan MDPI