Interesting article in Smithsonian Magazine about the Vitamin D & MS connection in relation to some interesting statistics. During the time after the Iranian Revolution in 1979 - when the mandate for modest dress and head coverings was instated - the rates of MS in Iran skyrocketed. The rates of MS increased by almost 7-fold over a 16-year period, and tripled during the just 4-year period of 2005-2009! Better diagnoses is likely explanation for part of this jump, but certainly can't be enough to fully explain this huge increase. In the article, one Iranian research speculates that an Iranian genetic tendency for MS is exacerbated by the severe lack of vitamin D caused by the clothing mandate.
The full article can be read online here.