While the tan summer is fading with November rains, comes a study that can help you make the most of exposure to the rays of the sun. We know that this is a difficult balancing act: too much sun can lead to skin cancer, too little to the Vitamin D deficiency and to depression; aesthetic considerations can further complicate matters for those who like to have tanned skin.
Sunstroke is the skin’s response to stress involving inflammation, cell proliferation, and repair of DNA damaged by ultraviolet radiation. This painful reaction can begin within minutes of cellular damage, while the production of dark pigmented melanin, which serves to protect against subsequent damaging attacks, takes hours or days.
The discovery of Carmit Levy of Tel Aviv University is that our skin’s response to the sun’s rays works on a 48-hour cycle.
“The results,” Levy said in a note, “were surprising: we expected a synchronization on a daily basis of the cell’s protective cycles.
The study was initially done on laboratory mice: those that were subjected to a cycle of exposure every two days developed darker-colored epidermal cells than those exposed every day or every three days, and more importantly, they did less damage to DNA.
The result was later confirmed for human skin as well. In both mice and humans, it is the MITF (short for melanogenesis associated transcription factor) protein that controls melanin production and its diffusion into neighboring cells, where it acts as a kind of microscopic sunshade. In both models, Levy found that MITF worked most effectively with exposure every 48 hours.
It is difficult to speculate why such a rhythm was formed in the human body, given that our ancestors exposed themselves to the sun every day, but Levy speculated that there is a connection with vitamin D produced by the skin, which is stable in the blood for 48 hours after sun exposure.
Malcov-Brog H, Alpert A, Golan T, Khaled M, Shen-Orr A, Levy C. UV-Protection Timer Controls Linkage between Stress and Pigmentation Skin Protection Systems. Molecular Cell Oct 25, 2018.
