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Melatonin Sleep biorhythm

The effect of artificial light on the hormonal balance

Alexander Wunsch

When the EU banned the sale of incandescent light the issue became the focus of public interest. Not only are the aspects of energy efficiency and sustainability; the potential consequences for our health also play an important role.

Light affects the organism through the skin and eyes. While sunlight on the skin cause different effects in the whole spectrum of the light spectrum, from the ultraviolet to the infrared, the eye can process only the optical radiation having a wavelength between 400 and 700 nm. In evolutionary terms, the eyes can be regarded as a projection of the diencephalon (inter brain), and they are co-ordinated in direct neuronal contact with this central point of control, where humoral and neural signals.

Up until about ten years ago believed retinohypothalamische device, the neural connection between the retina and diencephalon is only responsible for sending signals of brightness, while the light information is not collected by the photoreceptors of the retina, but ganglion cells, which they send to the diencephalon. Detailed examination of the ganglion layer recently revealed that approximately 5% of these cells contain a special pigment which is referred to as melanopsin, which makes them particularly susceptible to the wavelengths around 460 nm (= blue).

The higher the proportion of blue in the light, the stronger the signal that is sent to the inter-brain nuclei by the ganglion cell layer, where the suprachiasmatic nucleus is the main control point that includes the "internal clock". From there, there are optical fiber connections with the pituitary gland, pineal gland, and over the sympathetic nerve fibers to internal organs such as liver, kidney and heart. Pituitary and pineal constitute an antagonistic system, which is responsible for the coordinated control of vital autonomic functions associated with the circadian rhythm.

Energy-saving lamps and LEDs, which should replace incandescent lamps, send generally more blue light radiation and, therefore, affect the hormonal balance much longer than incandescent bulbs. This is especially severe at night because the production of the sleep hormone melatonin is suppressed. Melatonin synchronizes chronobiological rhythms and regulates regeneration processes in organ and cellular level. Recent scientific studies show the assumption that a low concentration of melatonin at night, the risk of certain hormone-related cancers such as breast and prostate cancer increases.

During the day, blue light increases the production of stress hormones such as cortisol, which reduces the responsiveness of the immune system. Therefore plays the proper treatment of artificial light an important role in disease prevention and is a new aspect in the treatment of hormone-related cancers. Especially those who already suffer from such a disease, should avoid light lamps and flat screens and protect their hormonal balance against unwanted influences by using special protective filters in the evenings, if necessary.

Alexander Wunsch, physician and photo-biologist, Heidelberg, GERMANY

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