Every cell in your body knows what time it is. Not because it has a watch, but because over millions of years it developed an internal rhythm tuned to the one reliable signal of the planet — the alternation of day and night. We call this rhythm circadian, and its chief conductor is light.
The discovery of the molecular mechanisms behind these internal clocks won the 2017 Nobel Prize in Physiology or Medicine. We now know the circadian rhythm affects not only sleep but almost everything: body temperature, hormone levels, digestion, immunity and cognitive performance.
A third type of light-sensing cell in the eye
Besides the rods and cones we see with, the retina has a third type of light-sensitive cell — ipRGC cells containing the pigment melanopsin. They are not for forming images. Their only job is to measure how much and what kind of light arrives and to send this information to the "master clock" in the brain (the suprachiasmatic nucleus).
Melanopsin is most sensitive to the blue component of light around 480 nm — exactly what fills the morning sky. Morning blue light is therefore the body's strongest signal for "it's day, time to wake and be active". The same signal, however, is counterproductive in the evening.
Melatonin: the hormone of darkness
As evening falls and blue light fades, the brain begins to release melatonin — the hormone that announces night and prepares the body for sleep and repair. The problem with the modern evening is that we drown it in artificial blue light from screens and LED bulbs. Melatonin is released later and less, and sleep comes later and shallower.
The result is a state chronobiologists call circadian misalignment: the internal clock says one thing, behaviour and lighting another. Over time it is linked to worse sleep, mood, metabolism and immunity.
How to use light in your favour
Chronobiology gives a surprisingly simple guide — it's about timing and type of light:
- More bright light in the morning — ideally outdoors, or at least strong indoor light. It reinforces the "day" signal and sets the clock.
- Enough light during the day — keeps you alert and stabilises the rhythm.
- Warm, dim light in the evening — limit the blue component so melatonin can form.
- Darkness at night — even faint light in the bedroom can suppress melatonin.
Where red and infrared light fit in
Interestingly, red and infrared light barely suppress melatonin, because melanopsin is not sensitive to them. Red and NIR therapy can therefore be part of an evening routine without disrupting sleep — unlike bright blue light. Conversely, a targeted morning dose of strong light helps "kick-start" the rhythm.
A full-spectrum panel lets you work with both ends of the day: a strong light stimulus in the morning, a regenerative dose of red and infrared in the evening. Thanks to independent channel control you can switch off the UV component and use only the wavelengths that suit the time of day.
Tune your day to light
HELIOR One gives you control over both the spectrum and the timing of therapy.
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