The results of a randomized and placebo-controlled trial were recently published in JAMA, evaluating the use of high-dose vitamin D among adults with clinically isolated syndrome (CIS). CIS is defined as the first neurological episode with similar symptoms to multiple sclerosis (MS). It lasts at least 24 hours, is caused by inflammation and demyelination, and may eventually progress to MS. The study was known as the D-Lay MS trial, a parallel, double-blind, randomized, placebo-controlled clinical trial in which 303 participants received either 100,000 IU cholecalciferol orally every 2 weeks for 2 years, or a placebo. The primary outcome of the study was the occurrence of a relapse and/or detection of new lesions (or increased intensity) by MRI.
The group given vitamin D had a significant 34% lower incidence of disease activity, with 74.1% of people receiving placebo and 60.3% receiving vitamin D demonstrating evidence of disease. The time until disease activity was detected was also delayed with vitamin D supplementation, occurring (on average) at 432 days into the trial vs. 224 days. Similarly, all variables measured by MRI were significantly improved by vitamin D compared to placebo. No adverse effects were attributed to vitamin D.
This is an encouraging study, as it suggests that vitamin D may help prevent or delay the development of MS among people with CIS. A relationship between MS and vitamin D has been established in a number of studies, with Mendelian randomization suggesting that low vitamin D levels may even be causal. It’s also worth noting that daily supplementation may be more effective, at least for increasing 25-OH vitamin D levels, than the biweekly supplementation implemented in this trial.