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.
For example, a small pilot study testing the effect of vitamin D for one year in 15 relapsing-remitting MS (RRMS) patients, suggested that vitamin D is safe and could reduce the rate of relapses. Conversely, a Finnish study conducted in 2012, suggested that vitamin D could reduce the number of new lesions but did not affect relapse rate.
Studies have shown that MS is more common in people who live further away from the equator possibly because they get less sunshine, and therefore less potential vitamin D. Other studies show that people who have been exposed to sunlight during childhood and adolescence or take vitamin D supplements have a lower risk of developing MS. Another study showed that there may be a relationship between people who are genetically predisposed to low vitamin D levels and those who are more likely to develop MS. Low levels of vitamin D in patients with clinically isolated syndrome (CIS) may be associated with an increased risk of this developing into MS.
While vitamin D is a naturally occurring substance, there are side effects associated with taking too much vitamin D. Side effects include hypercalcemia (too much calcium in the blood) which may affect the kidneys and cause bone pain, nausea and vomiting, psychological disturbances, and abnormal heart rhythm. According to the National Institute of Health (NIH), adults should not exceed 4000 IU (100 micrograms) of vitamin D per day.
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