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I was confused by the part that said white skin allows more sun light to be absorbed. I'm quite sure this is wrong: Dark skin means more light is absorbed, and

I was confused by the part that said white skin allows more sun light to be absorbed. I'm quite sure this is wrong: Dark skin means more light is absorbed, and therefore doesn't bounce back at the viewer's eyes. the only explanation I can think of is that the rules are somehow different for light outside the visible range?

slackerIII 17y ago
I'm guessing the absorption they are talking about happens below the pigment level.
nopassrecover 17y ago
Well the advantage of increased melanin in the skin is protection from UV damage. Perhaps this is what they are referring to.
pedermoeller 17y ago
As I remember the explanation: Dark skin means more melanin in the skin. Melanin blocks the UV light that the body uses to synthesize D vitamin. So white people in north are better suited for utilizing the scarce sunlight for D vitamin production and black people in the south are better protected against the skin cancer risk caused by the UV radiation.
igrekel 17y ago
I wouldn't dismiss this so quickly. It is widely accepted and is also part of what is evaluated when the doctor recommends or not that you give extra vitamin D to your child, having white skin means you need to spend less time in the sun to have sufficient vitamin D and not require supplements. Perhaps the question is more complex because sunlight is not all in the visible wavelengths and skin is actually translucent and light reaches different level through the skin, melanin prevents parts of the light to reach deeper levels in the skin and also converts parts of light.
giardini 17y ago
UV-B sunlight strikes a substance on the skin called 7-dehydrocholesterol converting it into vitamin D3. The vitamin D created by this reaction is then reabsorbed by the skin and enters the bloodstream. Apparently some new research indicates reabsorption may take up to 48 hours! Melanin inhibits the above reaction, so blacks need more sun to get the same amount of vitamin D. More details: http://www.cholesterol-and-health.com/Vitamin-D.html http://www.cholesterol-and-health.com/Vitamin-D.html

slackerIII 17y ago

I'm guessing the absorption they are talking about happens below the pigment level.

nopassrecover 17y ago

Well the advantage of increased melanin in the skin is protection from UV damage. Perhaps this is what they are referring to.

pedermoeller 17y ago

As I remember the explanation: Dark skin means more melanin in the skin. Melanin blocks the UV light that the body uses to synthesize D vitamin. So white people in north are better suited for utilizing the scarce sunlight for D vitamin production and black people in the south are better protected against the skin cancer risk caused by the UV radiation.

igrekel 17y ago

I wouldn't dismiss this so quickly. It is widely accepted and is also part of what is evaluated when the doctor recommends or not that you give extra vitamin D to your child, having white skin means you need to spend less time in the sun to have sufficient vitamin D and not require supplements. Perhaps the question is more complex because sunlight is not all in the visible wavelengths and skin is actually translucent and light reaches different level through the skin, melanin prevents parts of the light to reach deeper levels in the skin and also converts parts of light.

giardini 17y ago

UV-B sunlight strikes a substance on the skin called 7-dehydrocholesterol converting it into vitamin D3. The vitamin D created by this reaction is then reabsorbed by the skin and enters the bloodstream. Apparently some new research indicates reabsorption may take up to 48 hours! Melanin inhibits the above reaction, so blacks need more sun to get the same amount of vitamin D. More details: http://www.cholesterol-and-health.com/Vitamin-D.html http://www.cholesterol-and-health.com/Vitamin-D.html