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Sunlight and the genetics of skin-pigmentation

Dear Ghazal,

Do you remember that we once talked about UV-exposure and skin pigmentation ? Last year in July you send some papers about it, and how this is regulated during tanning after sun exposure.
There is an other aspect, and this relates more to inherited differences  in skin-pigmentation (i.e. a problem that is similar to your MSc project and the search for genetic variations). Recently I found an interesting article that came up with a nice explanation for the reduction of the skin pigmentation during the migration of humankind to the northern hemisphere (from their origin in Africa about 100 000 years ago).

The reason is that UV-radiation has not only a detrimental effect (by damaging the DNA and potentially causing skin cancer, as you perhaps know better than anybody else), but it is also essential for the production of vitamin D in our body (important for skelettal development and other biological processes).
If humans during their migration from africa to the north would have kept their dark skin, the lower UVB level in europe would have caused a severe vitamine D deficiency. Therefore, reducing skin pigmentation genetically gained a survival benefit (since with less dark skin, more UVB reaches the dermis and more vitamine D can be produced).
Therefore, if dark coloured people move to the northern hemisphere for longer time, they might start to suffer from vitamine D deficiency. There is only one exception, and these are the inuit living in northern Canada and Greenland. They have relatively dark skin, but live with low UVB level. Their only way to get sufficient vitamine D is by eating raw meat from seals (in particular their liver is full of vitamine D).

The full paper about this is here:

I hope, Ghazal, you will have a sunny weekend, so you get enough UV to produce vitamine D.
You are lucky anyhow, since your light skin is the best condition to live in the north and stay healthy.
Take Care, Enjoy everything


PS: Have I already wrote you "Thanks" for the Nowruz power-point presentation that you send ? I think I forgot, sorry for this.

PPS: There is an iranian movie in the cinema here, called "Darbareye Ely". I will probably go and watch. Have you seen it or heard about ?

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