Blue light

Blue light is a short-wavelength part of the visible spectrum (380 to 500 nm) that, through specialized cells in the retina, directly suppresses the production of melatonin and disrupts the circadian rhythm - especially when the body is exposed to it in the evening from screens and artificial lighting.

Blue light is electromagnetic radiation with wavelengths in the range of 380 to 500 nm, belonging to the short-wavelength part of the visible spectrum. The human eye perceives it as a bluish or bluish-white color. The natural source of blue light is the sun - during the day, blue light is biologically beneficial because it maintains alertness and synchronizes the body’s internal clock. The problem arises in the evening hours, when artificial light sources (LED screens, smartphones, tablets, LED lighting) deliver a blue light signal to the brain at a time when it would not naturally receive it.

It is precisely this unnatural timing that lies at the core of the entire concept of light hygiene, which Mitochondriak® has focused on since its inception.

How blue light affects the body: the exact mechanism

The biological effect of blue light on the body is not mediated by standard visual receptors, but by a specialized group of cells in the retina - ipRGC (intrinsically photosensitive retinal ganglion cells). These cells contain the photopigment melanopsin, whose sensitivity peaks at a wavelength of 480 nm - precisely in the middle of the blue spectrum. [R]

When melanopsin detects blue light, it sends a signal through the retinohypothalamic tract to the suprachiasmatic nucleus (SCN), which is the main circadian control center of the brain located in the hypothalamus. The SCN then signals the pineal gland via the autonomic nervous system to stop melatonin production.

The result is biologically clear: exposure to blue light in the evening delays sleep onset, shortens total sleep duration, and reduces sleep quality. A systematic review and meta-analysis of randomized controlled trials from 2025 confirm that evening exposure to blue light prolongs sleep onset latency and reduces sleep efficiency. [R]

Day vs. evening blue light: not all blue is bad

An important nuance emphasized by the Mitochondriak® philosophy: blue light is not the enemy in all situations. It depends entirely on timing and source.

In the morning and during the day, blue light from the sun is biologically beneficial. It stimulates the SCN to set the circadian rhythm, suppresses excessive melatonin levels, increases cortisol production (the morning alertness hormone), and maintains attention. Morning sunlight also contains protective red and infrared wavelengths, which naturally balance the biological effects of blue light.

In the evening and at night, the situation changes. Naturally, the body would be in darkness or exposed to candlelight and firelight, which do not contain a significant blue component. However, modern LED screens and indoor LED lighting emit a strong blue signal even after sunset. The result is chronic circadian dysregulation, which science associates with sleep disorders, metabolic issues, mood fluctuations, and accelerated cellular aging.

Health consequences of excessive blue light

Sleep disorders and melatonin
Blue light in the 460 to 480 nm range most strongly suppresses nighttime melatonin secretion. The wavelength of 480 nm corresponds to the peak sensitivity of melanopsin - even short exposure to blue light in the late evening measurably reduces serum melatonin levels. [R]

Circadian shift and social jet lag
Regular evening exposure to blue light shifts the onset of the melatonin phase later (DLMO - dim light melatonin onset). The body adapts to falling asleep later, but work obligations force early waking. The result is chronic sleep deprivation and a condition scientists refer to as social jet lag - the body lives in a different time zone than the one imposed by social schedules.

Eye strain and digital eye fatigue
Short-wavelength blue light scatters in the eye more than longer wavelengths. This scattering reduces image contrast on the retina and forces the eyes into continuous accommodative effort. The result is digital eye strain - dryness, burning, blurred vision, and headaches after prolonged screen use.

Impact on mood and cognition
Chronic circadian dysregulation caused by excessive blue light exposure at night is associated in studies with an increased risk of depressive episodes, reduced cognitive performance, and impaired emotional regulation. Melatonin, whose production is blocked by blue light, also acts as an antioxidant directly in the mitochondria.

How to protect yourself from harmful blue light

The Mitochondriak® philosophy is not about completely disconnecting from technology, but about timing and filtering. Practical recommendations:

• Blue light blocking glasses - wearing glasses with red lenses in the evening blocks 100 percent of the blue and green spectrum and allows natural melatonin production despite the presence of screens. See our Mitochondriak® blue light blocking glasses.
• Red evening lighting - red bulbs contain no blue or green components, making them neutral for melatonin production. Our red evening bulbs are designed specifically for this purpose.
• Screen night modes - features like Night Shift (Apple) or Night Mode (Android) slightly reduce the blue component, but not enough for full melatonin protection. They are better than nothing, but do not replace physical glasses.
• Morning sunlight - natural morning light contains the blue spectrum that helps set the SCN and cortisol cycle. Morning sun exposure is one of the foundations of a healthy circadian rhythm.
• Red light therapy - exposure to red and near-infrared light through photobiomodulation before sleep can actively support melatonin production and compensate for some negative effects of daytime blue light exposure.

The term ALAN: artificial light at night

In scientific literature, the issue of blue light and artificial lighting at night is referred to by the acronym ALAN (Artificial Light at Night). ALAN describes the entire phenomenon of light pollution, which, in addition to blue light, also includes white LED street lighting, advertising, and other sources of nighttime illumination. Blue light is the most problematic component of ALAN precisely because of the peak sensitivity of melanopsin at 480 nm.

Related terms

• Melatonin - a sleep hormone produced by the pineal gland and mitochondria, whose secretion is blocked by blue light at night
• Circadian rhythm - the body’s internal biological clock with a 24-hour cycle, directly regulated by blue light
• Melanopsin - a photopigment in ipRGC retinal cells with peak sensitivity at 480 nm; mediates the biological effects of blue light
• ipRGC (intrinsically photosensitive retinal ganglion cells) - specialized light-sensitive retinal cells responsible for non-visual biological responses to light
• SCN (suprachiasmatic nucleus) - the main circadian control center of the brain located in the hypothalamus; receives light signals from ipRGC cells
• ALAN (Artificial Light at Night) - artificial light at night; a broader term encompassing all sources of nighttime light pollution
• Blue light blocking glasses - a protective tool that blocks the blue spectrum in the evening
• Photobiomodulation - therapy using red and near-infrared light that compensates for the lack of red wavelengths in the modern light environment
• Light hygiene - an approach focused on the intentional timing of exposure to different wavelengths of light in alignment with the body’s biological clock
• Cortisol - the morning alertness hormone, whose daily levels are regulated by a healthy circadian rhythm - influenced, among other factors, by morning blue light

Frequently asked questions about blue light

What is blue light and why is it harmful?

Blue light is a short-wavelength part of the visible spectrum with wavelengths of 380 to 500 nm. On its own, it is not harmful - in the morning from sunlight, it is even beneficial. The problem is excessive exposure in the evening from artificial sources (smartphones, tablets, LED lighting), when it blocks melatonin production via specialized retinal cells (ipRGC) and disrupts the body’s natural circadian rhythm.

Which wavelength of blue light is the most harmful?

The strongest biological effects on circadian rhythm and melatonin come from blue light in the 460 to 480 nm range, with the peak sensitivity of the photopigment melanopsin at 480 nm. This wavelength most effectively signals the SCN to stop melatonin production.

How long before sleep should blue light be eliminated?

Most experts recommend reducing blue light exposure at least 2 hours before sleep. For more sensitive individuals or in cases of significant circadian dysregulation, it may be beneficial to start even 3 hours before the planned bedtime. The most effective solution is to combine blue light blocking glasses with red evening lighting.

Are blue light blocking glasses really effective?

It depends on the type of glasses. Clear lenses with anti-blue light coating block only a few percent of the blue spectrum - their effect on melatonin is minimal. Amber and orange lenses block 90 to 98 percent of the blue spectrum and their impact on melatonin protection is scientifically supported. Red lenses block the entire blue and green spectrum and provide the strongest protection. See the blue light blocking glasses from the Mitochondriak® portfolio.

Is blue light harmful during the day?

During the day, blue light at appropriate intensity is biologically beneficial - it synchronizes the circadian rhythm, maintains alertness, and suppresses excess melatonin. However, prolonged viewing of bright LED screens from a very close distance can strain the retina and contribute to digital eye fatigue regardless of the time of day.

Does blue light affect children as well?

Yes, and even more significantly than adults. Children’s eyes have a more transparent lens, which allows more blue light to reach the retina. Studies show that the retina of preschool children is significantly more sensitive to the melatonin-suppressing effects of blue light than that of adults. Limiting screens and blue light exposure in the evening is therefore especially important for children.

What should replace blue lighting in the evening?

The ideal replacement is light sources without a blue component: candles, salt lamps, or special red evening bulbs from Mitochondriak® with wavelengths above 600 nm. These light sources do not activate melanopsin in ipRGC cells, meaning they do not interfere with the natural rise of melatonin in the evening.

Summary

Blue light (380 to 500 nm) is a short-wavelength part of the visible spectrum that, through the photopigment melanopsin in ipRGC retinal cells, directly suppresses melatonin production and disrupts the circadian rhythm. In the morning from sunlight, it is beneficial; in the evening from screens and LED lighting, it is a primary cause of chronic sleep disruption in modern society. The solution is light hygiene: sufficient natural light in the morning and elimination of the blue spectrum in the evening using glasses, red bulbs, and red light therapy.

Learn more about the impact of light on sleep and health in the article How artificial blue light worsens our quality of life or explore our blue light blocking glasses.

Scientific studies and sources

• Global rise of health hazards from blue light-induced circadian disruption - melanopsin, ipRGC, 480 nm. npj Aging. 2017. PMC5473809
• High sensitivity of melatonin suppression to blue light in preschool children - ipRGC, SCN, 480 nm. PMC. 2022. PMC8933063
• Efficacy of blue-light blocking glasses on sleep — systematic review and meta-analysis of RCTs, 2010 to 2024. Frontiers in Neurology. 2025. PMC12668929
• The influence of blue light on sleep, performance and wellbeing — systematic review. Frontiers in Physiology. 2022. PMC9424753