According to a new study from Johns Hopkins, vitamin D blocks damage-causing immune cells from migrating to the brain in mice with a rodent form of multiple sclerosis (MS) - which may be how the so-called ‘sunshine vitamin’ prevents MS symptoms in humans as well.
MS is believed to be an autoimmune disorder in which the immune system wrongly attacks a person's own cells - leading to symptoms such as blurred vision, weakness and numbness. An estimated 400,000 Americans between the ages of 20 and 50 years are afflicted with MS. Typically, it affects two to three times as many women as men.
Health experts became interested in the possible role of vitamin D in MS when it became clear that the disease is more prevalent in regions farthest from the equator where there is less sunshine - the main natural source of vitamin D.
The Johns Hopkins study shows that vitamin D works by preventing immune cells from getting into the brain - a treatment method that has the potential to be as effective as, and is likely to be safer than existing drugs used to treat MS.
Johns Hopkins researchers simultaneously gave mice the rodent form of MS and a high dose of vitamin D - which protected the mice from showing symptoms of the disease. They found a large number of immune T cells in the blood of the mice, but very few in their brains and spinal cords. In other words, it looks as though T cells are being kept away from these areas.
However, the immunosuppressive effects of vitamin D appear to be fleeting - once it is withdrawn, MS-like flare-ups occur very quickly in these mice.
Clinical trials are ongoing to determine whether vitamin D supplementation can actually prevent or slow the progression of MS in humans. This may offer an opportunity in the future to study samples taken from participants in these trials, to see whether vitamin D has the same effect on human cells as it does in mice.