Many experts believe that vitamin D is important because exposure to sunlight can reduce the incidence and severity of MS. When the sun's UVB rays hit the skin, they produce vitamin D, a hormone that is important for good health generally, but particularly for people with MS, because it dampens overactive immune responses and also protects brain cells.
But in many parts of the world, sunlight is too scarce to produce enough vitamin D, so supplementation is needed. Research has shown that people with MS have lower levels of vitamin D, and also that vitamin D levels are lower during MS relapses.
We recommend that people ask for a vitamin D level test immediately upon being diagnosed with MS. That first level is often low, which may be what brings on the attack. It should be above 150nmol/L (60ng/mL in the USA).
If very low, it can be brought up quickly with a one-off megadose of vitamin D followed by regular capsules. Don't be nervous about large doses; research shows they are safe and actually necessary to raise Vitamin D levels quickly.
For more information on all these topics, please see the MS Encyclopedia.