Oh my gosh. I was googgling Hugh Downs and came across your page and  I am so glad I did!  I have not been diagnosed with MS HOWEVER, I have been struggling for years with all of the symptoms you have described and then some. I have seen countless Drs and not one has been able to help me .   My visual problems are the most depressing and scary at times.  But  I  will get to the subject of VIT. D deficiency... my last vit. D  result was 5. I take 50,000 IU's once a week for 4 weeks then get rechecked.   It does go up to normal but falls back down to well below normal within a few weeks.  I never  really notice too much difference in how I feel when my levels are normal.