This is an excellent @50 minute long presentation by Michael Holick, PhD, MD conducted on May 5, 2007 (this is best viewed in IE and a very special thanks to Drew for posting this to the MS-Diet list).
Most of our human population on the entire planet is walking around deficient in Vitamin D. Even in Saudi Arabia, Mexico, India, etc.
While watching the above I kept thinking about this BBC documentary on global dimming (and you thought global warming was the problem.....it's not that simple.....).
I wonder if the global dimming experts are talking to Dr. Holick's research group. They should be.