| We probably wouldn't even expect it to be a straight correlation with "the higher your latitude, the lower your vitamin D." Skin color is very tightly coupled with latitude, with melanin concentrations evolved to let in a small window of sunlight that (1) allows enough production of vitamin D and (2) prevents destruction of folic acid. (A few exceptions can be found in communities that have historically eaten large amounts of fish, such as Inuits, who tend to have skin color slightly darker than "expected" because they are getting more vitamin D from diet, and so the the folic acid side of the fitness function "wins.") Given that, we shouldn't necessarily expect populations whose ancestors have been at one latitude for hundreds/thousands of years, and who get plenty of out-door time, to necessarily be vitamin D deficient. What is more likely to contribute to higher vitamin D deficiencies in a population would be (1) immigration/expatriation of people to higher latitudes (even over the course of hundreds or thousands of years) and (2) living indoors more. Naturally, this may result in a hodge-podge of communities with vitamin D deficiencies, which may not be clearly correlated with latitude (although may still show correlation). |