Summer Solstice: Light as a Nutrient
What if light wasn’t only something you see, but something your body listens to — a quiet signal guiding your sleep, your energy, and the rhythm of your entire inner world?
For thousands of years, humans have lived in step with the sun.
Now, modern science is revealing that this ancient relationship wasn’t just symbolic - it was biological.
Ancient Wisdom, Modern Clarity
Long before screens and indoor living, our days rose and fell with sunlight.
We woke with the sunrise, slowed down at sunset, and spent evenings surrounded by the warm glow of firelight - gentle, familiar, and in tune with our physiology.
Across cultures, the summer solstice marked a moment of reverence. Bonfires, music, and rituals weren’t just celebrations - they were expressions of our deep connection with light.
Early eyes were not designed for the sharp vision we know today. They began as simple light sensors that helped living beings tell day from night and sync their internal rhythms with the external world.
Today, our light environment has changed dramatically - and our biology feels those changes.
With the southern hemisphere’s summer solstice approaching on 21 December, we’re invited to reconnect with nature’s oldest rhythm.
A New Lens: How Light Affects the Body
Science shows that light is one of the most powerful signals your body receives.
It influences:
sleep
energy
mood
metabolism
temperature
hormone timing
cellular processes
Light essentially tells your body: “This is what time it is.”
The Daylight Storyline
Each part of the day carries its own biological message:
🐦Dawn
Soft red and near-infrared light gently prepares your body to wake.
🌄Sunrise
A rise in blue light triggers the brain to set the circadian clock.
🧘♀️Morning
UVA wavelengths begin to appear, influencing hormonal rhythms and daily functions.
☀️Midday
The brightest visible light of the day boosts alertness and mood.
🌅Sunset
Warm reds return, signalling your body to unwind and begin producing melatonin.
🌃Night
Darkness allows restoration, repair, and deep sleep processes to unfold.
Your Inner Clockwork
Light shapes your physiology through grounded, observable mechanisms:
Through your eyes
Specialised photoreceptors send signals directly to the brain’s master clock, regulating sleep–wake timing, hormones, temperature, and more.
Through your skin
Light-sensitive molecules called chromophores absorb certain wavelengths, triggering biochemical responses.
Through the Spectrum of Light Itself
Not all light is the same - and your body doesn’t respond to every wavelength in the same way.
Different spectrums of sunlight appear at different times of day, acting like a natural language your body has learned over millions of years:
Infrared (IR) & Near-Infrared (NIR):
Abundant at dawn and dusk, these longer wavelengths penetrate deeply into tissues. They support cellular energy processes and signal the body that it’s either easing into the day or preparing to rest.UVA:
Appearing in the morning once the sun rises higher, UVA light influences nitric oxide release, blood flow, and certain hormone pathways. It’s part of the signal that the day has truly begun.UVB:
Present only when the sun is high enough in the sky, UVB enables the skin to synthesise vitamin D - but only during a limited window of the day and season. Its presence tells your body it’s midday.
Each wavelength acts as a time cue, reinforcing internal rhythms.
Combined, they help your cells understand the full arc of the day: wake, energise, stabilise, unwind, repair.
Through your rhythms
Your circadian system influences:
alertness
appetite and digestion
metabolic health
mood regulation
immune function
hormonal balance
Light is the primary synchroniser of these rhythms.
Movement and meal timing act as secondary time cues - but light leads the orchestra.
A Grounded Way to See Yourself
Your body is rhythmic, not mechanical.
It uses electrical signals.
Its cells emit faint glimmers of light during metabolism.
It responds to cycles in nature.
These aren’t metaphors - they’re biology.
For decades, messaging has focused mainly on the dangers of sunlight.
Protection is important, but avoidance has left many people disconnected from the natural timing cues our species evolved with.
This isn’t about midday sunbathing.
It’s about daily relationship - gentle, gradual, respectful.
Know your skin type.
Honour your limits. Start slowly.
Simple Ways to Re-Align With Light
You don’t need equipment, special routines, or major lifestyle changes.
Just small, intentional moments:
✨ Step outside within 30–60 minutes of waking
✨ Watch the sunrise when you can
✨ Gradually allow more skin exposure as seasons warm
✨ Open windows to let in a fuller light spectrum
✨ Take brief outdoor breaks during your workday
✨ Cover up when UV levels are high opting for low tox sunscreens only
✨ Switch to warm, dim light in the evening
✨ Keep your bedroom dark at night
✨ Watch the sunset and let it help you unwind
These aren’t chores — they are grounding rituals that reconnect you with the natural rhythm you were designed for.
Exploring light and grounding has shaped my own health journey, and I hope that even a single small insight here might illuminate a spark of wellbeing in yours. x Kat
References
Evolution of eyes & light detection
Nilsson, D.-E. (2009). The evolution of eyes and visually guided behaviour. Philosophical Transactions of the Royal Society B, 364(1531), 2833–2847.
Gehring, W. J. (2005). New perspectives on eye development and the evolution of eyes and photoreceptors. Journal of Heredity, 96(3), 171–184.
Circadian rhythms & light
Roenneberg, T., & Merrow, M. (2016). The circadian clock and human health. Current Biology, 26(10), R432–R443.
Light-sensitive cells
Berson, D. M., Dunn, F. A., & Takao, M. (2002). Phototransduction by retinal ganglion cells that set the circadian clock. Science, 295(5557), 1070–1073.
Light spectra & melatonin timing
Stothard, E. R. et al. (2017). Circadian entrainment and melatonin suppression to naturalistic light-dark cycles. Current Biology, 27(12), 1734–1740.
Artificial light at night
Chang, A.-M. et al. (2015). Evening use of light-emitting eReaders negatively affects sleep. PNAS, 112(4), 1232–1237.
Heath, M. et al. (2014). Circadian misalignment in humans: A review. Endocrine Reviews, 35(6), 1077–1097.
Biophoton emission
Van Wijk, R. (2014). Light in Shaping Life: Biophotons in Biology and Medicine. Meluna Research.
Photobiology & skin
Young, A. R., & Narbutt, J. (2019). Ultraviolet radiation and the skin. Medicine, 47(2), 109–113.
Quantum biology (evidence-based aspects)
Lambert, N. et al. (2012). Quantum biology. Nature Physics, 9, 10–18.
Scholes, G. D. et al. (2017). Using coherence to enhance function in chemical and biophysical systems. Nature, 543, 647–656.
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