Can we prevent or treat multiple sclerosis by individualised vitamin D supply?

Apart from its principal role in bone metabolism and calcium homeostasis, vitamin D has been attributed additional effects including an immunomodulatory, anti-inflammatory, and possibly even neuroprotective capacity which implicates a possible role of vitamin D in autoimmune diseases like multiple sclerosis (MS). Indeed, several lines of evidence including epidemiologic, preclinical, and clinical data suggest that reduced vitamin D levels and/or dysregulation of vitamin D homeostasis is a risk factor for the development of multiple sclerosis on the one hand, and that vitamin D serum levels are inversely associated with disease activity and progression on the other hand. However, these data are not undisputable, and many questions regarding the preventive and therapeutic capacity of vitamin D in multiple sclerosis remain to be answered. In particular, available clinical data derived from interventional trials using vitamin D supplementation as a therapeutic approach in MS are inconclusive and partly contradictory. In this review, we summarise and critically evaluate the existing data on the possible link between vitamin D and multiple sclerosis in light of the crucial question whether optimization of vitamin D status may impact the risk and/or the course of multiple sclerosis

Clinical implications of a possible role of vitamin D in multiple sclerosis

Hypovitaminosis D is currently one of the most studied environmental risk factors for multiple sclerosis (MS) and is potentially the most promising in terms of new clinical implications. These practical consequences, which could be applied to MS patients without further delay, constitute the main purpose of this review. Vitamin D is involved in a number of important general actions, which were not even suspected until quite recently. In particular, this vitamin could play an immunomodulatory role in the central nervous system. Many and varied arguments support a significant role for vitamin D in MS. In animal studies, vitamin D prevents and improves experimental autoimmune encephalomyelitis. Epidemiologically, latitude, past exposure to sun and the serum level of vitamin D influence the risk of MS, with, furthermore, significant links existing between these different factors. Clinically, most MS patients have low serum levels of vitamin D and are in a state of insufficiency or even deficiency compared to the international norm, which has been established on a metabolic basis. Large therapeutic trials using vitamin D are still lacking but the first results of phase I/II studies are promising. In the meantime, while awaiting the results of future therapeutic trials, it can no longer be ignored that many MS patients have a lack of vitamin D, which could be detected by a serum titration and corrected using an appropriate vitamin D supplementation in order to restore their serum level to within the normal range. From a purely medical point of view, vitamin D supplementation appears in this light to be unavoidable in order to improve the general state of these patients. Furthermore, it cannot currently be ruled out that this supplementation could also be neurologically beneficial

Farming, foreign holidays, and vitamin D in Orkney

Orkney, north of mainland Scotland, has the world's highest prevalence of multiple sclerosis (MS); vitamin D deficiency, a marker of low UV exposure, is also common in Scotland. Strong associations have been identified between vitamin D deficiency and MS, and between UV exposure and MS independent of vitamin D, although causal relationships remain to be confirmed. We aimed to compare plasma 25-hydroxyvitamin D levels in Orkney and mainland Scotland, and establish the determinants of vitamin D status in Orkney. We compared mean vitamin D and prevalence of deficiency in cross-sectional study data from participants in the Orkney Complex Disease Study (ORCADES) and controls in the Scottish Colorectal Cancer Study (SOCCS). We used multivariable regression to identify factors associated with vitamin D levels in Orkney. Mean (standard deviation) vitamin D was significantly higher among ORCADES than SOCCS participants (35.3 (18.0) and 31.7 (21.2), respectively). Prevalence of severe vitamin D deficiency was lower in ORCADES than SOCCS participants (6.6% to 16.2% p = 1.1 x 10(-15)). Older age, farming occupations and foreign holidays were significantly associated with higher vitamin D in Orkney. Although mean vitamin D levels are higher in Orkney than mainland Scotland, this masks variation within the Orkney population which may influence MS risk