RESULTS / DISCUSSION Both cross-sectional and longitudinal studies have fairly consistently demonstrated a strong positive correlation between  vitamin D deficiency and subsequent relapse and /or disability in patients with MS .
As well , there appears to be a negative correlation between vitamin D levels and inflammatory markers in MS patients , suggesting that vitamin D modifies serum cytokines to a more anti-inflammatory profile .
However , the criteria of temporality , dose-response , and experimental evidence are yet to be adequately met , although there is preliminary evidence from longitudinal studies and r and omized clinical trials ( RCTs ) of supplementation that vitamin D can attenuate the autoimmune response in patients , and potentially reduce relapse rates and burden of disease .
Ultimately , the current evidence does not permit inference of a causal relationship between vitamin D deficiency and disease activity in MS .
INTRODUCTION Given that vitamin D has a role in immunomodulation , and its levels appear to correlate with the development of Multiple Sclerosis ( MS ) , it is conceivable that vitamin D may also influence disease activity in MS patients .
In this regard , we conducted a systematic review investigating the evidence for : ( 1 ) the role of vitamin D in disease activity in MS , and ( 2 ) the therapeutic supplementation of vitamin D in MS .
Lower serum vitamin D levels are associated with a higher relapse risk in multiple sclerosis
Objective : There is increasing evidence that vitamin D can be protective against the development of multiple sclerosis ( MS ) , but it may also be beneficial for the clinical course of the disease . Our objective was to prospect ively investigate if 25-hydroxy-vitamin D ( 25-OH-D ) levels are associated with exacerbation risk in MS in a study with frequent serum measurements . Methods : This was a prospect i ve longitudinal study in 73 patients with relapsing-remitting MS .  Blood sample s for 25-OH-D measurements were taken every 8 weeks . Associations between 25-OH-D levels and exacerbation rates were assessed using Poisson regression ( generalized estimating equations ) with the individual serum levels as time-dependent variable . Results : During follow-up ( mean 1.7 years ) , 58 patients experienced a total of 139 exacerbations . Monthly moving averages of 25-OH-D levels were categorized into low ( < 50 nmol/L ) , medium ( 50–100 nmol/L ) , and high ( > 100 nmol/L ) levels . Exacerbation risk decreased significantly with higher serum vitamin D levels : respective relative exacerbation rates for the medium and high-level category as compared to the low-level category were 0.7 and 0.5 ( p value for trend : p = 0.007 ) . The association between 25-OH-D concentrations and exacerbation rate was log linear without a threshold . With each doubling of the serum 25-OH-D concentration the exacerbation rate decreased by 27 % ( 95 % confidence interval 8%–42 % , p = 0.008 ) . Conclusions : Our finding that higher vitamin D levels are associated with decreased exacerbation risk in relapsing-remitting MS suggests a beneficial effect of vitamin D on disease course in MS . However , the possibility of reverse causality can not be ruled out completely . R and omized intervention studies are therefore needed to investigate the effect of vitamin D supplementation in MS
RESULTS / DISCUSSION Both cross-sectional and longitudinal studies have fairly consistently demonstrated a strong positive correlation between  vitamin D deficiency and subsequent relapse and /or disability in patients with MS .
As well , there appears to be a negative correlation between vitamin D levels and inflammatory markers in MS patients , suggesting that vitamin D modifies serum cytokines to a more anti-inflammatory profile .
However , the criteria of temporality , dose-response , and experimental evidence are yet to be adequately met , although there is preliminary evidence from longitudinal studies and r and omized clinical trials ( RCTs ) of supplementation that vitamin D can attenuate the autoimmune response in patients , and potentially reduce relapse rates and burden of disease .
Ultimately , the current evidence does not permit inference of a causal relationship between vitamin D deficiency and disease activity in MS .
INTRODUCTION Given that vitamin D has a role in immunomodulation , and its levels appear to correlate with the development of Multiple Sclerosis ( MS ) , it is conceivable that vitamin D may also influence disease activity in MS patients .
In this regard , we conducted a systematic review investigating the evidence for : ( 1 ) the role of vitamin D in disease activity in MS , and ( 2 ) the therapeutic supplementation of vitamin D in MS .