This post really helped me. I was taking Vitamin D but only in my multi vitamin and this is not enough. My G.P told me that nearly everyone she tested was deficient. She doesn't test anymore unless the patient insists.  I now take D and in the liquid form. Last week, I asked my neurologist and he told me that it is very important. My question is why didn't he tell me this 10 years ago or during any of the subsequent office visits? He is aware of the significance of vitamins and a healthy diet. So, thank you for this post and especially for the footnotes. Please continue to help us. When it comes to MS, I feel that I am a detective with ever changing clues and also my own advocate in the medical arena. This discussion board is very helpful.