I got my copy of the MSCA (Multiple Sclerosis Center of Atlanta) Spring 2012 newsletter today.
It can be viewed online at
http://www.mscatl.org/file/11.Spring2012Newsletter.pdf.
There's an article about supplements and which ones people with MS should not take (it's on page 3 at the bottom left of the page).
Coenzyme Q10, Melatonin, Grape Seed Extract, Vitamin A and Vitamin C (greater than 1,000 mg/day) are a few of the supplements listed that surprised me. The reason they gave was that these have the potential to stimulate the immune system or interfere with medication.
Now I'm wondering if I should stop taking my multi-vitamin. My Neuro has never mentioned anything about these supplements.

I take, in addition to a multi-vitamin, Astaxanthin 10mg. daily and Vitamin D3 10,000 IU daily. To be honest I haven't felt any different with it than I did without it but that doesn't mean it's not having some benefit.
There is also a list of supplements that interact negatively with steroids.