Re: Why do white people tan?
Date: August 23, 2013 11:58AM
What is a Tan?
Melanocytes are special skin cells that produce melanin (skin pigment) when they are exposed to ultraviolet light in sunlight. The pigment absorbs UV radiation in sunlight, so it helps to protect skin cells from UV damage. Your body actually produces two kinds of pigmant. One is called eumelanin and it is responsible for the golden brown color we normally associate with tanning. Another pigment is called phaeomelanin and it produces a red color. Redheads and blondes produce more phaeomelanin and less eumelanin, which is why they don't tan as well.
How Does Your Body Know It's Sunny Out?
Sunlight (or UV light from tanning beds) affects the pituitary gland (a gland at the base of the brain that secretes hormones) which then produces MSH (melanocyte-stimulating hormone). This hormone flows through the bloodstream to the melanocytes, which makes them able to produce more melanin. Since the pituitary gland is tied into the optic nerve, (the nerve in your eyes that lets you sense light), wearing sunglasses makes you tan less. Weird.
Tanning and Race
Different races tan differently (and some don't tan at all). Caucasians (white people) and other lighter skinned races tan the way explained above. People of darker races produce melanin continuously (without having to go in the sun), which means their skin is always pigmented (dark) to varying degrees. People of dark races are much less likely to get skin cancer because their cells are constantly protecting them from UV radiation.