Does vitamin D play a role in multiple sclerosis? – ECTRIMS 2015
European Committee for Treatment and Research in MS (ECTRIMS) – 31st Congress – Barcelona, Spain, October 7-10, 2015 – Multiple sclerosis is more common in countries farther away from the equator, which suggested that a lack of sunlight may predispose people to developing MS. The skin uses sunlight exposure to produce vitamin D, which the body then uses to build bone and maintain the functioning of the immune response. So this led to the idea that vitamin D, as a hormone that modulates the immune response, may provide a treatment benefit in MS.
Many studies have now investigated different aspects of the vitamin D story, including several presented at this year’s ECTRIMS meeting. Vitamin D research encompasses a number of questions, so let’s look at each of these in turn.
Are people with low vitamin D levels at higher risk of developing MS? Several population-based studies have indicated that lower vitamin D levels are associated with an increasing risk of an array of autoimmune disorders, and the strongest link is for thyroid disease and MS (Skaaby and colleagues. Endocrine 2015;50:231-238). An ongoing multinational study is EnviMS, which is looking at different environmental factors. The study recently reported that in Norway, people who took cod liver oil (a good source of vitamin D) during adolescence were 33% less likely to develop MS (Cortese and colleagues. Mult Scler 2015; epublished May 6, 2015). Cod liver oil didn’t appear to influence MS risk if it was taken in childhood, which suggests that the teen years are especially important to the development of MS in most people. EnviMS has also found that higher sun exposure during childhood and adolescence appears to reduce the risk of developing MS later on (Magalhaes and colleagues. ECTRIMS 2015; abstract P794). This effect was shown for people in Canada and Italy, but not for Norway (so perhaps taking cod liver oil offset the need for more sun).
Is sunlight/vitamin D equally important for everyone? MS is most common in Caucasians of northern European heritage, and it appears that a vitamin D-MS link doesn’t necessarily apply to people of other racial/ethnic backgrounds. The main function of skin pigmentation is to screen out the harmful effects of sunlight, so it’s not surprising that blacks are reported to have significantly lower vitamin D levels compared to whites (Gelfand and colleagues. Neurology 2011;76:1824-1830). Despite this, MS is much less likely to occur in blacks in Africa. Among African-Americans, MS is more common but low vitamin D levels have been shown to have no impact on the severity of their MS (Gelfand 2011). This may be because their bodies are much more efficient at using vitamin D (Avasarala and Zachariah. J Neurol Sci 2015;358:417-418), but this is only one of many possible explanations.
There are many difficulties in trying to compare MS across different racial/ethnic groups because there are so many confounding variables. This was shown in an analysis of MS-related health claims for whites, African-Americans and Hispanics in the U.S. (Langer-Gould and colleagues. ECTRIMS 2015; abstract P280). The overall conclusion was that low vitamin D levels were a risk factor for developing MS only in whites – the same wasn’t true for African-Americans or Hispanics. However, it should be noted that the groups were not all that well-matched with respect to other possible MS risk factors, such as smoking, obesity and mononucleosis during the teen years. Whites were twice as likely to be smokers and to have had mononucleosis during adolescence compared to the other groups; blacks were significantly more likely to be obese; and Hispanics were younger and much less likely to have a family history of MS. It will take more study to tease out the impact of vitamin D from amid the many genetic and environmental factors that may contribute to a person’s MS risk.
Does low vitamin D make MS worse? Several studies have reported that people with MS who have low vitamin D levels have more relapses and more inflammatory flare-ups on their MRI (Ascherio and colleagues. JAMA Neurol 2014;71:306-314; Fitzgerald and colleagues. JAMA Neurol 2015; epublished October 12, 2015). The most recent study reported that people with an early form of MS (called clinically isolated syndrome, or CIS) were less likely to have tissue damage in the brain if their vitamin D levels were higher (Fitzgerald and colleagues. ECTRIMS 2015; abstract P799). Another recent study found that people with low vitamin D levels had a greater risk of developing disability (Thouvenot and colleagues. Eur J Neurol 2015;22:564-569).
However, the evidence is less than clear-cut. One recent study found that low vitamin D was associated with nerve damage in MS (Sandberg and colleagues. Mult Scler 2015; epublished October 13, 2015). But a different study found that vitamin D levels had no impact on the process of neurodegeneration (Fjeldstad and colleagues Mult Scler Relat Disord 2014;3:489-493). It’s more likely that vitamin D modulates the immune response in various ways (Thomas and colleagues. ECTRIMS 2015; abstract P401; Toghianifar and colleagues. J Neuroimmunol 2015; epublished August 15, 2015), and any effects on nerve function are the indirect result of inflammation. This would explain the observation that vitamin D status appears to have little impact on a person’s level of disability or their risk of developing progressive disease (Muris and colleagues. ECTRIMS 2015; abstract P400).
Vitamin D supplements are often recommended for people with MS. While the evidence of a benefit is unclear, supplements (or sun exposure) may be worth a try. They’re an inexpensive add-on to an MS medication that may help to normalize the immune response.
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