The Influence of Artificial Light on the Hormonal Balanceby Alexander Wunsch
When the EU prohibited the sale of incandescent light bulbs, the topic light became the focus of public interest. Not only are there the aspects of energy efficiency and sustainability; the possible consequences for our health play an important role as well.
Light affects the organism via the eyes and the skin. While sunlight on the skin causes different effects in the whole range of the light spectrum, from ultraviolet to infrared, the eye can only process the optical radiation with a wavelength between 400 and 700 nm. In evolutionary terms, the eyes can be regarded as a protrusion of the diencephalon (interbrain) and are in direct neuronal contact with this central control point, where humoral and neuronal signals are coordinated.
Until about ten years ago, it was believed, that the retino-hypothalamic apparatus , the neural connection between retina and diencephalon is only responsible for sending signals of brightness, while the light information is not gathered by the retina´s photoreceptors, but by ganglion cells, which send them on to the diencephalon. Detailed examination of the ganglion layer recently revealed that about 5% of these cells contain a special pigment called melanopsin, that makes them especially sensitive to the wavelengths around 460nm (=blue).
The higher the proportion of blue in the light, the stronger are the signal sent from the ganglion cell layer to the interbrain cores, where the nucleus suprachiasmaticus is the main control point, which contains the “inner clock”. From there, there are fibre connections to the pituitary gland, the pineal gland as well as, via sympathetic nerve tracts, to inner organs like liver, kidneys and heart. Pituitary and pineal gland form an antagonistic system, that is responsible for the coordinated control of vital vegetative functions in connection to the circadian rhythm.
Energy saving lamps and LEDs, which are supposed to replace incandescent lamps, generally emit more blue light radiation, and therefore influence the hormonal balance much more than incandescent lamps. This is especially grave in the nighttime, because the production of the sleep hormone melatonin is surpressed. Melatonin synchronizes chronobiological rhythms and regulates regeneration processes on organ and cell level. Recent scientific studies allow for the assumption that a low concentration of melatonin at night increases the risk of certain hormone-related cancers, such as breast and prostate cancer.
During the day, blue light increases the production of stress hormones such as cortisol, which reduces the reactive capacity of the immune system. Therefore the right handeling of artificial light plays 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 condition should avoid the light of energy saving lamps and flat screens, and protect their hormonal balance from unwanted influences by using special protective filters in the evening hours, as necessary.
Alexander Wunsch, physician and photo-biologist, Heidelberg, GERMANY firstname.lastname@example.org