Individuals with ancestors from different parts of the world can have highly visible differences in skin pigmentation. Individuals with Sub-Saharan African ancestry (black people) tend towards darker skin, while those of Northern European descent (white people) have paler skin. Between these extremes are individuals of Asian, South-East Asian, Native American, Middle Eastern, Polynesian and Melanesian descent.
The skin of black people has more variation in color from one part of the body to another than does the skin of other racial groups, particularly the palms of the hands and soles of the feet. Part of this is the result of the variations in the thickness of the skin or different parts of the body. The thicker the skin, the more layers of cell with melanin in them, and the darker the color. In addition, these parts of the body do not have melanin-producing cells.
Darker skin hinders UV A rays from penetrating. Since vitamin B folats are degraded by UV A and vitamin D is synthesized different skin tones are more likely to produce different vitamin deficiencies.
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