Vitamin D supplements are currently being investigated as a potential therapy to treat multiple sclerosis (MS). Vitamin D can be found in some foods, especially fatty fish, but most daily vitamin D is received naturally through exposure to sunlight. It can also be taken as a supplement.
There are a large number of research groups worldwide assessing the potential role of vitamin D in the onset, progression, and treatment of MS in both preclinical and clinical studies.
How vitamin D works in MS
MS symptoms are caused by the immune system mistakenly targeting the myelin sheath, a protective layer that surrounds nerve fibers. The immune system causes inflammation in the brain and spinal cord and the damage to the myelin sheath results in disrupted nerve signaling and eventual permanent nerve damage.
Among its many roles, vitamin D is essential in maintaining healthy bones (as it helps absorb nutrients like calcium). However, research is uncovering that vitamin D may have properties altering the immune system and is active in the brain and spinal cord – that it can alter the immune response.
To exert an effect, vitamin D binds to a protein called the vitamin D receptor, which triggers a response in the cell. This receptor has long been known to be present in immune cells, and in the brain and spinal cord. Vitamin D may be able to block the production and maturation of key immune cells involved in the inflammatory response (T- and B-cells), as well as regulating the secretion of cytokines (small proteins that can trigger inflammation).
A promising study from the Cambridge Centre for Myelin Repair has shown that vitamin D may play a role in myelin repair. In MS, the levels of oligodendrocytes (myelin making cells) can decrease, as they are killed and not replaced, compounding the myelin damage as more is not being made. The Cambridge research team found that the vitamin D receptor can pair with an existing protein involved in myelin repair, the RXR gamma receptor. Adding vitamin D to brain cells where the proteins are present increased the production of oligodendrocytes by 80 percent. The study shows that vitamin D may be involved in the regeneration of myelin from the onset of the disease. This research has been published in the Journal of Cell Biology.
Research into how vitamin D could affect MS is ongoing such as work into how vitamin D can influence the MS-associated gene HLA-DR or whether vitamin D is involved in the movement of T-cells.
Vitamin D in clinical trials for MS
Many clinical trials have been carried out to assess whether vitamin D supplements can treat MS. In general, the results are promising, however, most are small-scale and therefore lacking in statistical power, and problems such as ensuring each patient receives a known dose of vitamin D has made it difficult to get conclusive results.