The Great Debates: Sun Exposure and Health

Sunglasses have long been a staple of modern "health" and wellness — they protect our eyes, reduce glare, and help us feel comfortable in bright conditions. But in recent years, a question has started to circulate in the health and biohacking world.

Do sunglasses interfere with your body’s natural light cycles and hormones?

The concern comes from a very real and important truth: natural light exposure is crucial for circadian health. Your body’s internal clock relies on signals from sunlight to regulate sleep, energy, mood, and hormone production.

So let’s break it all down — the facts, the myths, and how to use sunglasses in the most effective way possible.

We’ve all heard about how light affects our sleep and hormones, and probably to avoid screens at night, get morning sunlight, dim the lights in the evening — all great advice. But here’s a surprising twist: it’s not just your eyes that matter when it comes to your internal clock. Your skin can actually sense light too — and it may play a bigger role in your circadian rhythm and hormone health than we ever thought. Recent research has increasingly highlighted the role of skin photoreceptors as a potentially more deterministic factor in regulating hormone production and circadian rhythms than the well-studied receptors in the eyes.

Unlike ocular photoreceptors, which are primarily responsible for processing visual information and transmitting signals to the brain’s suprachiasmatic nucleus (SCN), skin photoreceptors may offer a more direct and distributed mechanism for detecting environmental light cues across the entire body.

Melanopsin, a photopigment once thought to exist only in the retinal ganglion cells, has been discovered in the skin, suggesting that skin cells can independently respond to light exposure. This broader surface area of light detection can influence systemic physiological processes, including the modulation of melatonin and cortisol levels, potentially offering a more pervasive and sustained impact on circadian regulation.

Skin photoreceptors are less restricted by ocular limitations such as blinking, eyelid closure, and pupil constriction (or sunglasses). This means that the skin is often exposed to ambient light for longer durations throughout the day, even under sub-threshold levels that may not trigger a significant ocular response.

Some of the latest evidence indicates that UV and visible light exposure on the skin can stimulate hormonal cascades such as the production of beta-endorphins and vitamin D, which, in turn, influence mood, immune function, and sleep-wake cycles.

Given this capacity for light absorption and hormonal signaling without direct involvement of the visual system, skin photoreceptors may represent a more consistent and holistic regulatory mechanism for circadian rhythms and endocrine balance.

Let’s go ahead and take a deep dive into this fascinating connection between skin, light, and your body’s natural rhythms.

Your Circadian Rhythm is More Than Just Sleep

Your circadian rhythm is your body’s 24-hour internal clock. It controls:

• When you feel sleepy or alert

• The timing of hormone release (like melatonin and cortisol)

• Body temperature, digestion, immune function, and more

We often think of the eyes as the “gatekeepers” of light. Specialized cells in your eyes detect light, especially blue light, and send signals to your brain’s master clock — the suprachiasmatic nucleus — to sync your rhythm with the day-night cycle.

That’s why blue light at night can delay melatonin and mess with your sleep. But it turns out, your skin has its own way of detecting light too.

Your skin isn’t just a protective barrier — it’s biologically active and surprisingly smart. Studies show that skin cells like keratinocytes and melanocytes contain photoreceptors — proteins that can sense light, including:

• Opsin 2 (rhodopsin)

• Opsin 3 (encephalopsin)

• Opsin 5 (neuropsin)

These skin photoreceptors respond to sunlight, especially UV and blue light. While they’re best known for regulating pigmentation (hello, tanning!), they also impact DNA repair, immune activity, hormones, and even circadian signaling in the body’s peripheral clocks.

The brain’s master clock isn’t working alone. Almost every organ — your liver, gut, skin, and even your muscles — has its own local clock. These are called peripheral clocks, and they can be influenced by food, temperature, and yes — light on your skin.

In fact, some researchers believe that light hitting the skin may help synchronize these peripheral clocks, even if it doesn’t go through your eyes. That means sunlight on your skin might support healthy hormone rhythms, metabolism, and sleep, even if you’re not staring into the sun.

What This Means for Hormones

Light through the eyes is known to regulate melatonin and cortisol — two big players in your energy and stress levels. But light on the skin may also influence these hormones indirectly, through your peripheral clocks.

Some studies suggest that:

• Morning sunlight on the skin may help align cortisol rhythms

• Red and infrared light (like sunrise or photobiomodulation therapy) may support mitochondrial function and circadian balance

• Full-spectrum sunlight is more effective than artificial light for synchronizing biological rhythms — especially when it hits both your eyes and your skin

Why Indoor Living Might Be Messing With Your Rhythm

Here’s the kicker: most of us spend 90% of our time indoors, under artificial lighting that filters out UV and infrared light — the very wavelengths your skin uses to regulate its clock.

Add to that clothes, sunscreen, and windows, and your skin might be missing out on crucial circadian cues. This could lead to:

• Brain fog and poor sleep

• Hormonal imbalances

• Mood swings or low energy

• Slower recovery and immune challenges

While your eyes are still a part of circadian regulation, your skin is an unsung hero that’s deeply connected to your body’s light-sensing system. Understanding this gives us a more holistic way to approach sleep, hormones, and health. This brings us back to our original question...

Does wearing sunglasses impact our circadian rhythms and subsequent endocrine function?

Where Sunglasses Fit Into the Picture

Sunglasses filter out certain wavelengths of light, especially UV and visible blue light — the very ones that influence circadian rhythms. So, it’s reasonable to wonder: if you wear sunglasses, are you blocking these important hormonal signals?

The answer: not necessarily.

Here’s what really matters:

1. Timing is Everything

Wearing sunglasses during the first 1–2 hours after sunrise might reduce your body’s ability to fully “wake up” hormonally. That’s when natural blue light triggers a healthy cortisol spike and sets your internal clock for the day.

What to do instead:

Try to get 10–20 minutes of unfiltered morning light on your face and through your eyes (no sunglasses or windows). You don’t need to stare at the sun — just being outside is enough.

2. It’s About Total Daily Light Exposure

If you wear sunglasses only during peak daylight (like at noon or in intense sun) but spend time outside in the morning or evening without them, you’re likely getting plenty of light cues. Hormonal issues don’t come from wearing sunglasses — they come from spending too much time indoors under artificial lighting.

Bottom line: Don’t stress about wearing shades during mid-day walks, driving, or beach trips — especially if the light is harsh or uncomfortable. This can also be very damaging to your eyes and in these instances the risks outweigh the potential benefits of skipping wearing them.

3. Sunglasses Have a Purpose: Eye Protection

In high-glare environments (water, snow, desert, or high altitude), sunglasses protect your eyes from damage, not just from UV rays but from intense visible light that can contribute to headaches, eye strain, and long-term vision problems.

Your hormonal health depends on your circadian rhythm, not on squinting through painful sunlight.

4. When You Might Be Overdoing It

Here are some cases where sunglasses might interfere with your natural rhythm:

• You wear them all day, even in moderate or indoor lighting

• You wear them in the early morning, every day, without ever getting direct light

• You rarely go outside without them

If that’s the case, your body may not be getting the natural light cues it needs. But the solution isn’t to ditch sunglasses entirely — it’s to balance their use with time outdoors in natural light.

Practical Tips for Reconnecting your Skin to Light and Hormonal Health

• Morning light is medicine: Get 10–30 minutes outside each morning (without sunglasses is recommended)

• Use sunglasses strategically: Wear them when light is too bright or during prolonged exposure

• Don’t wear sunglasses indoors or at dusk

• Dim lights at night and avoid screens before bed to support melatonin production

Sunglasses aren’t your enemy — artificial light deprivation is and this is influenced by how much your skin is exposed to natural light, not just your eyes. If you’re worried about how much natural and artificial light is impacting your hormones, start by getting more natural light in the right moments. That means prioritizing early sunlight exposure and spending more time outdoors overall. Make sure to reconnect your skin to natural light regularly. To do this you don’t have to sunbathe for hours (and you shouldn’t — moderation is key!). And there are many ways to make sure that you are reconnecting your body to the sun, we have covered quite a few in this article but if you have more questions or would like to discuss this more please feel free to email me and I would love to connect with you!

So go ahead — wear your shades when you need them! Just make sure your skin, body, and your brain are still getting the appropriate natural light exposure you need to stay balanced, energized, and in rhythm with the world around you.

References

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Gooley, J. J., Lu, J., Chou, T. C., Scammell, T. E., & Saper, C. B. (2001). Melanopsin in intrinsically photosensitive retinal ganglion cells regulates sleep. Nature, 425, 327–331. https://doi.org/10.1038/nature01922

Khalsa, S. B. S., Jewett, M. E., Cajochen, C., & Czeisler, C. A. (2003). A phase response curve to single bright light pulses in human subjects. The Journal of Physiology, 549(3), 945–952. https://doi.org/10.1113/jphysiol.2003.040477

LeGates, T. A., Fernandez, D. C., & Hattar, S. (2014). Light as a central modulator of circadian rhythms, sleep and affect. Nature Reviews Neuroscience, 15, 443–454. https://doi.org/10.1038/nrn3743

Turner, P. L., & Mainster, M. A. (2008). Circadian photoreception: Ageing and the eye’s important role in systemic health. British Journal of Ophthalmology, 92(11), 1439–1444. https://doi.org/10.1136/bjo.2008.141747

Brainard, G. C., Hanifin, J. P., Greeson, J. M., Byrne, B., Glickman, G., Gerner, E., & Rollag, M. D. (2001). Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. The Journal of Neuroscience, 21(16), 6405–6412. https://www.jneurosci.org/content/21/16/6405