If we are more susceptible to MS because of a lack of Vitamin D - any suggestions on what I should be taking, how many / much a day, and where I can get it from.
Here's one perspective on vitamin D. The Mayo Clinic suggest that doses higher than 2000 IU/day be avoided due to toxicity problems. They also state that blood levels of 25(OH)D3 levels may be significantly elevated, although 1,25(OH)2D3 levels may be normal. Thus, hypercalcemia really needs to be addressed as well.http://www.mayoclinic.com/health/vitami ... t-vitamind
recommends 1000 IU/day for sunlight deprived individuals.
Overall, it's kind of confusing right now since there are so many different "recommended" dosages. I tend to think that it's best to err on the side of caution when beginning a new regimen or modifying a current one. Here in the US, the RDA for vitamin D is 400 IU and many multivitamins contain this amount. Starting out with 400 IU should be safe. As Melody suggested, increasing the dosage should probably be done after a period of time to allow the body to become adjusted. However, to what level it should be increased to is likely still up for debate (I certainly don't have the answer).
The scales are different for other vitamins by the way. Very strange, I think. Holford says IU's are an old measurement unit.
To the best of my recollection, IUs are a measure of the specific activity of the stuff that's being analyzed. Each vitamin (or enzyme or whatever) will likely have a different assay that's performed in order to determine its specific activity. When a substance is listed as x amount of IUs, then you have to know which assay was performed in order to determine the value. Sometimes, the type of assay performed is a standard to the substance being tested and the numbers should be comparable between different sources. However, having worked in a lab and having dealt with chemical supply companies, I know that there are many cases were only "units" are assigned to a substance (particularly with enzymes) and these are often not comparable as the assays differ between various suppliers. Yes, it's about this time that one becomes prone to developing headaches.