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18. February 2014

Health effects of the light

Role of light and its effects on sleep

During the last decades, a popular opinion on the role of light and its health effects has been significantly changed due to scientific research. The light can affect one´s perception, change the mood, make one comfortable or uncomfortable and regulate the circadian rhythm (24-hour cycle of sleep and being awake vs. basal body temperature). All these findings have changed our opinion on artificial light. The most important discovery is the third type of photoreceptors in human´s eye. These photoreceptors are sensitive to blue range of light spectrum and are able to affect a production of melatonin.

Photoreceptors affecting the production of melatonin


Tretí druh fotoreceptorov v ľudskom oku

These photoreceptors are sensitive to blue range of the light spectrum, to the wavelength in the range of 464 nanometres. They can affect the production of melatonin, a hormone that manages the circadian rhythm. (Source: OMS Lighting)

Possitive effects of melatonin

Melatonin is known as “hormone of darkness and sleep”. It makes your sleep good and your dreams sweet. However, there are more benefits for our body:

  • Melatonin affects the bloodstream, body temperature, carbohydrate metabolism, lipid metabolism and protein metabolism,
  • It affects production of sex hormones, immune system,
  • It affects the aging process, behaviour and psychological reactions,
  • It makes your sleep good and your dreams sweet.

Melatonin is often considered to be the hormone that affects the aging process and immune system. Anyway, there is another quality that has been recently discovered: melatonin inhibits the growth of some types of malignant cells. 

Consequences of melatonin production decrease

Lack of melatonin can cause sleep disorders or even sleeplessness. Lately, a hypothesis on negative effects of artificial light on production of melatonin was formulated. Excessive light levels during the night emitted by lamps, televisions, computers or public lighting can cause melatonin production decrease.

If the body is exposed to the light during the time when the melatonin is supposed to be produced, the risk of cancer development is elevated.

A Harvard study conduced on 78 586 nurses, the incidence of cancer was proved to be 35% higher for the group with at least three night shifts in a month during 15 or more years. 

The melatonin levels in the blood rise after dark. The most is being produced in the middle of the night. But if the room is not dark enough, the production of melatonin is inhibited. If the body is exposed to monochromatic blue light (so called cool white), the production of melatonin is inhibited, too.

Health effects of daylight

Vplyv denného svetla na ľudský organizmus

Cortisol, a hormone that stimulates the metabolism, is being produced in the morning time. Its concentration in the blood reaches a peak at about nine o´clock and decreases continually during the day. Melatonin, a hormone of sleep, is being produced during the night. Its concentration in the body reaches a peak at about three o´clock. (Source: OMS Lighting)

Nowadays, we spend much time in offices, where only the artificial light and no daylight are present. During the day, we lack the daylight and during the night, we lack the normal darkness. Therefore, the normal production of melatonin cannot take place.

How to stimulate the normal production of melatonin?

  • Keep your sleep and getting up regular,
  • Sleep in the darkness and in a calm place (curtains closed, lights turned off, blinking devices, TV and computer stand-by lights covered),
  • Spend your evening with dim light and pleasant yellow and orange light,
  • If you need to get up during the night, do not use white light. Red light is more suitable, as it does not disrupt the production of melatonin.


  • OMS Lighting, ELITE (2013)
  • MUDr. Miroslav Mikulecký st., Pozor na nočné (hlavne modré) svetlo! Medicínsky monitor, (2005), s. 32-34
  • Doc. RNDr. Bernadetta Pástorová, PhD., časopis Bedeker zdravia, (2012)
  •, (2010)
  •, (2010)

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