Dr. Soilu-Hänninen and colleagues from the University of Turku in Finland recently conducted a double blind, placebo-controlled trial of vitamin D in 66 MS patients, to see if it helped as an add-on therapy with interferon.
Soilu-Hänninen M, Aivo J, Lindström BM, Elovaara I, Sumelahti ML, Färkkilä M, Tienari P, Atula S, Sarasoja T, Herrala L, Keskinarkaus I, Kruger J, Kallio T, Rocca MA, Filippi M. A randomised, double blind, placebo controlled trial with vitamin D3 as an add on treatment to interferon β-1b in patients with multiple sclerosis. J Neurol Neurosurg Psychiatry. 2012 83(5):565-71.
They found that 20,000 IU of vitamin D3 once a week resulted in significantly fewer lesions on brain MRI and strong trends toward lower lesion burden, reduced disability scales, and improved ability to walk, compared to controls. 25(OH)D levels only went from 22 ng/ml to 44 ng/ml in one year.
The authors note that other studies have found that in children with possible MS, each 4 ng/ml decrease in 25(OH)D has been correlated with a conversion to definite MS. Lower serum 25(OH)D values have been associated with a higher rate of MS relapses. Researchers have correlated each 4 ng/ml increase in 25(OH)D with up to 12% reduction in relapse rate in adults with MS, and each 10 ng/ml increase in 25(OH)D with a 34% decrease in relapse rate in childhood MS.
Remember, observational studies (unlike the RCT above) are likely studying the effect of sunshine, not supplements, and the 25(OH)D levels are more likely to be a reflection of how much sun exposure a subject gets than whether they are taking a supplement or not.
In spite of the above findings in a randomized controlled trial, I would never recommend only oral vitamin D for people with MS. They may well benefit from sunshine or low-pressure sun tanning beds as well.
Until it is clear oral vitamin D can fully replace sunshine, make sure all MS patients take at least 5,000 IU of vitamin D per day and sun bathe daily at midday. In the winter, use low-pressure sunbeds, the ones that replicate high intensity sunlight, on a regular basis.