The Forgotten Light: The Vital Role of the Sun Beyond Vitamin D

The Forgotten Light: Why the Sun Is Not Just About Vitamin D

by Laurent Glatz – for Athletic Carnivore

We have learned to view the sun as a danger, an aggression, almost a mistake of nature that must be avoided at all costs. Yet, the human body was not built inside closed offices, under fluorescent lights, behind filtering windows, or staring at screens until midnight. It was built outdoors, in a harsh and precise alternation between natural light and darkness. The real question may not be whether the sun is good or bad. The real question is what happens to a human organism when one of its oldest biological signals is removed day after day.

For a long time, the debate was reduced to a simple idea: sun equals vitamin D. If we lack sun, then taking a vitamin D capsule would suffice. This view is convenient, modern, reassuring. It reduces a living phenomenon to a blood measurement. It gives the impression that a pill can replace the sky, warmth, horizon, the day-night cycle, and the full spectrum of sunlight. But biology is rarely that simple. Vitamin D is important, of course. But it may only be the visible part of a much larger phenomenon.

The body does not perceive light only through the skin. It perceives it through the eyes, the brain, mitochondria, the hormonal system, and the circadian rhythm. Morning light does not have the same effect as a phone screen at 11 p.m. The sun low on the horizon has a different signature than the vertical midday sun. Light passing through modern glass is not necessarily the same as light directly touching the skin. Reducing all this to a simple question of vitamin D is like summarizing human nutrition as just calorie counting.

Mitochondria are at the heart of this story. Often called the cell’s power plants, this image is too limited. A mitochondrion does not just produce energy. It manages oxidative stress, participates in metabolism, influences inflammation, communicates with the rest of the cell, and determines a tissue’s functional capacity. Brain cells, heart cells, liver cells, muscle cells, or retinal cells have different needs, but all depend on proper energy production. When this production declines, it is not just abstract fatigue. It is a drop in the efficiency of life itself.

With age, chronic disease, metabolic overload, inflammation, or sedentary lifestyle, mitochondria can become less efficient. The body then produces less energy, handles oxidative waste poorly, and enters a deep slowdown. In the liver, this can promote fat accumulation. In muscles, it can result in poor recovery. In the brain, it may manifest as brain fog, memory loss, or mood instability. In the immune system, it can alter the ability to respond properly to threats.

This is where light becomes fascinating. The sun does not only emit ultraviolet rays that trigger vitamin D production. It also emits red and infrared light, some wavelengths of which penetrate deeper into tissues. These wavelengths do not behave like mere surface light. They seem to interact with mitochondria, particularly through systems linked to the respiratory chain, oxidative stress, and local production of protective molecules.

Among these molecules, melatonin deserves a fresh look. Commonly, melatonin is known as the sleep hormone, produced in the evening by the pineal gland to signal the body it’s time to sleep. But this view is incomplete. There is also melatonin produced locally within cells, especially at the mitochondrial level. This melatonin is not just a night signal. It acts as an internal antioxidant, a kind of biological cooling system that helps the cell better manage oxidative stress generated by energy production.

This is a crucial point. When a mitochondrion produces energy, it also produces a form of biological heat—not just thermal heat, but oxidative heat. Like a running engine, it must avoid overheating. If the protective system is insufficient, energy becomes costly. The cellular engine runs less efficiently, waste accumulates, the cell deteriorates, and inflammation rises. Infrared light could partly stimulate these protective mechanisms. This is not magic. It is an interaction between an ancient environmental signal and cellular machinery that evolved alongside it.

This perspective completely changes our relationship with the sun. The sun is no longer just a dermatological risk to manage. It becomes a metabolic regulator. This does not mean one should burn their skin, deny the risks of excess, or confuse smart exposure with brutal exposure. It means that permanent avoidance of the sun also raises a biological question. A body deprived of natural light is not neutral. It must operate with impoverished signals, overly dark days, overly bright nights, and a confused internal clock.

The circadian rhythm is probably the other major piece of the puzzle. In the morning, light entering the eyes informs the brain that the day has begun. It sets the internal clock, influences morning cortisol, alertness, mood, body temperature, digestion, insulin sensitivity, and nighttime melatonin secretion. In the evening, darkness should signal the opposite: slow down, repair, sleep, restore. Yet modern life often does exactly the reverse. Days are dark, spent indoors. Nights are bright, saturated with screens, LEDs, notifications, and nervous stimulation.

This reversal is biologically incoherent. The body receives a night message during the day, then a day message during the night. It no longer clearly knows when to activate, digest, repair, or sleep. We then talk about fatigue, stress, lack of motivation, fragile sleep, sugar cravings, and poor recovery. But behind these symptoms, there is sometimes a simpler problem: the nervous system no longer receives the right signals at the right time.

In a well-managed carnivore or low-carb approach, this question becomes even more interesting. Much is said about stable blood sugar, low insulin, nutrient density, animal proteins, natural fats, satiety, and reducing processed foods. All of this is central. But human energy does not depend solely on what we eat. It also depends on how the body transforms that fuel. A nutrient-dense diet can provide the materials, but mitochondria still have to produce energy, manage oxidative stress, support the nervous system, and enable recovery.

This is probably one of the modern mistakes: believing health can be fully contained in the plate, supplements, or medication. Nutrition is fundamental, but it is not alone. A steak eaten by a body that sleeps poorly, never sees the sun, lives under chronic stress, and spends its days sitting under artificial light will not produce the same effects as a steak eaten by a body exposed to morning light, active, well-oxygenated, rested, and metabolically stable. Nutrition provides the matter. Light provides part of the signal.

Vitamin D remains important, but it should not serve as an excuse to forget the rest. A person can take vitamin D and still be deprived of natural infrared light, morning light, coherent circadian rhythm, and nighttime darkness. Conversely, a person regularly exposed to the sun receives a complete biological spectrum: visible light, infrared, ultraviolet depending on time, latitude, season, and skin type. Supplements can correct a deficiency. They do not necessarily replicate the full biological experience of natural exposure.

The issue of hospitals is revealing. For a long time, some facilities had verandas, open windows, outdoor spaces. The patient was not just lying under artificial light, isolated from day and night. Today, one can spend weeks in a dark room, without direct sunlight, with broken rhythms, machines, noise, screens, scheduled meals, and a total loss of natural cues. Modern medicine knows how to save lives in emergencies. But it sometimes forgets that the body also recovers thanks to simple signals: light, sleep, air, movement, heat, cold, contact with the outside.

This is not about falling into the naive idea that the sun cures everything. That would replace one simplification with another. It is about restoring light to its place: a major biological factor, probably underestimated, that dialogues with mitochondria, the brain, immunity, sleep, mood, and metabolism. The sun is not a medicine in the modern sense. It is older than that. It is a functional signal.

Modernity has trapped us in a strange contradiction. We want more energy, more focus, more immunity, more sleep, more longevity, yet we often live opposite to what our biology expects. We eat under artificial light, work without sun, look at screens at night, sleep with a brain still illuminated, then seek solutions in a pill, an app, a stimulant, or a new protocol.

Perhaps human health does not start only on the plate. Perhaps it also starts in the morning, when the body finally understands that it is daytime. Perhaps energy is not just a matter of calories, but a matter of signals. And perhaps one of the greatest paradoxes of our time is fearing the sun while living in a fatigue that the absence of light may help perpetuate.

If the human body was built under the sky, what becomes of it when it spends its life avoiding it?

#Sun #Mitochondria #VitaminD #MetabolicHealth #CircadianRhythm #Carnivore #LowCarb #CellularEnergy #Sleep #Inflammation #AthleticCarnivore