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Anonymous
I RAGEEEE every time somebody says UV-->tan.
Tan=pigment (eumelanin) released from special "skin" cells (melanocytes). If you want to get tan, you want to increase your eumelanin.
How do you increase eumelanin? Sunlight, clearly. The biological purpose of a tan is to combat UV light.
Sunlight --> UV light --> body senses "danger" (UV light=DNA damage via thymine dimers etc=non buono) --> special cells (keratinocytes) secrete melanocyte-stimulating hormone (MSH) --> other special cells (melanocytes) are induced to produce melanin (eumelanin=brown/tan, phaeomelanin=red) from that MSH --> melanin "reflects" UV light, preventing potential DNA damage in the future
Sunscreen blocks UV light from your skin, so your body won't get as strong a "danger" signal, so it won't make so much MSH-->melanin-->tan. However, studies have shown that even just wearing sunglasses can decrease your "level" of tan, so clearly there's more to it than just how much sun your skin gets.
TL;DR (unless you want to be nerd-ed out):
>>449069 Both are dangerous obviously. Tanning beds are just more dangerous because they deliver a much higher "dose" of UV than sunlight would. The "healthiest" tan would be from gradual "doses" of natural sunlight,so your body had time to recover from the damage and build melanin defenses.
>>449092 Sunscreen would decrease how tan you got, but you would still be slightly darker.
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