What Is the Circadian Rhythm
Your circadian rhythm is the body’s internal 24-hour clock. It synchronises everything from hormone release and body temperature to digestion, mood and cellular repair.
This rhythm relies on light cues — the rising and setting of the sun — to know when to activate wakefulness and when to prepare for rest. When light and dark cycles become irregular, the brain and skin fall out of sync, and energy, mood and repair capacity decline.
Light into the Eyes: Why It Matters
When natural morning light enters the eyes, specialised photoreceptors in the retina (called intrinsically photosensitive retinal ganglion cells) send a signal to the brain’s master clock, the suprachiasmatic nucleus. This tells the body it’s daytime.
In response, cortisol rises gently to promote alertness and focus, while melatonin — the sleep-inducing hormone — switches off until evening. This morning reset anchors the entire circadian rhythm for the day.
Artificial light cannot fully replicate the specific wavelengths of early sunlight, especially the blue-enriched, low-intensity light of dawn that the body recognises as a “time cue.”
Why Morning Light Balances the Circadian Rhythm
Consistent early-morning light exposure helps stabilise sleep–wake patterns, hormone production and metabolic function.
It supports:
-
Sleep quality: by reinforcing the timing of night-time melatonin release.
-
Mood and energy: through serotonin production, which converts to melatonin later that evening.
-
Immune function and inflammation control: via regulation of cortisol and autonomic balance.
-
Cellular and skin repair: by synchronising peripheral clocks in tissues throughout the body, including the skin.
When circadian rhythm is misaligned — late nights, screen exposure, irregular waking times — melatonin secretion weakens, inflammatory markers rise, and both systemic and cutaneous repair slow down.
