Sunlight: Between Cure and Caution

by Dr. Alexander Wunsch, M.D., Ph.D.

Abstract:

Sunlight: Friend & Foe

Many biohackers treat sunlight as a cure-all. But like any medicine, it’s the dose, timing, and context that make the difference.

Sunlight heals—but only if your body is ready. Gradual adaptation is key: start with 3–5 minutes at noon, increase slowly over a week, max out at ~20–30 minutes. After that, more is not better.

Once the cure is done, protection matters:

• Shield skin from damage

• Protect eyes from cataracts & ARMD

But watch out: standard sunglasses often block circadian light, especially brown and grey tints.

BlueSync is a next-gen eyewear tech:

• Filters harmful UV & HEVL

• Preserves circadian-effective light

• Lets repair-active NIR through

It’s not about more sunlight—it’s about smart sunlight.

Science ≠ self-service. Use light wisely.

Introduction:

The introduction of BlueSync has triggered a debate that centers on the paradigm of sunlight exposure and the value and extent of protection against potentially harmful overexposure. 

Many in the biohacking world proclaim sunlight as the ultimate panacea, a universal elixir for vitality. But this view oversimplifies a deeply complex biological reality. If there is a sensor, there is always something to detect—and most likely something to protect. Evolution doesn’t waste energy: sensors exist because the stimuli they monitor have the potential to harm.

Sunlight can be healing—but only when exposure is cautious, calibrated, and individually adapted. All benefits from sun exposure are byproducts of the body’s protective cascades. These cascades only yield positive outcomes when they are forced to overcompensate for the stress imposed—something that depends heavily on dose, timing, context, and individual resilience.

The success of heliotherapy wasn’t due to blind exposure to the sun—it was due to diligence and precise application. For example: a proper adaptation phase should last at least a week, starting with 3–5 minutes of noontime exposure (when UVB is highest), gradually increasing by 3–5 minutes daily, if no adverse reactions occur. A therapeutic dose is typically reached at 20–30 minutes. Beyond that, additional exposure often yields no further benefit—and can even become harmful. After 3–4 weeks of therapeutic doses, a pause might be necessary. As with any therapy, sunlight must not be applied at the therapeutic dose indefinitely—heliotherapy should only be used for the duration of illness, and possibly recovery.

And after healing? Protection becomes key. The optimal dose and overdose calculations depend on skin type, resilience, and numerous additional individual factors. Exposures beyond the ideal individual dose for optimal health maintenance require skin and ocular protection to prevent long-term risks like photoaging, skin cancer, cataract, and macular degeneration. However, conventional sunglasses—especially with brown or grey tints—often suppress circadian stimulation by filtering out blue light around 480 nm, which is crucial for chronobiological regulation.

New Technology:

This is where BlueSync enters the picture. It’s not the problem—it’s part of the solution for those who are exposed to sunlight or are using blue light protection glasses indoors and still want to maintain proper circadian entrainment.

BlueSync is a novel protective eyewear technology designed to filter harmful short-wave radiation (UV and HEVL), while preserving the beneficial elements: it maintains circadian-effective blue light and allows repair-active near-infrared (NIR) to pass through. Although the filter has a bluish tint, it doesn’t increase the overall blue content. Instead, it modulates incident light toward a higher correlated color temperature while significantly reducing overall light transmission—especially the more damaging shorter wavelengths.

BlueSync opens a new chapter in light hygiene. It bridges the need for protection with the need for biological stimulation—a balancing act modern life increasingly demands.

Let’s be clear:

• Thesis (e.g., WHO): Sunlight is dangerous and easily overdosed.

• Antithesis (e.g., some biohackers): You can’t get enough sunlight.

• Synthesis: Sunlight is both life-saving and potentially harmful—it’s all about how you use it.

Science is not a self-service shop where you cherry-pick only what fits your belief system. Sunlight is medicine—but only when prescribed with intelligence.

Dr. Alexander Wunsch, MD, PhD, is a German physician, light therapist, scholar and non-fiction author who specializes in researching the effects of light on human health. He has given numerous lectures on topics such as light therapy, the impact of artificial light on chronobiology and the importance of natural light for the human organism. His work has helped to deepen the understanding of how light affects our biological clock and various physiological processes. As scientific consultant and inventor he is involved in the development of products and technologies for the improvement of human health and wellbeing.

Developed in collaboration with the world’s leading expert in photobiology, BlueSync is the first lens scientifically designed to strengthen the circadian rhythm during the day.

Today is a special day in the Northern Hemisphere: The Winter Solstice. This annual milestone brings with it a unique blend of astronomical wonder and cultural significance. The Winter Solstice also brings significant changes to biological life on Earth. For example:

• Animals adapt by migrating, hibernating, or altering their behavior and physiology. Think of a bear hibernating in a cave.
• Plants enter a period of dormancy, responding to the light and temperature changes. Many plants lose their leaves and their energy descends into the roots, rather than the branches.

Now, how does the Solstice impact cultural life on Earth?