A new study from researchers in France has found that taking high doses of vitamin D every two weeks may help reduce disease activity in people with very early stages of multiple sclerosis (MS). The study was led by scientists from CHU Nîmes, Université Montpellier, and several MS centers in France and was published in the journal JAMA.
MS is a long-term condition that affects the central nervous system, including the brain and spinal cord. It often begins with a single episode of symptoms such as blurred vision, numbness, or muscle weakness. This first episode is called clinically isolated syndrome (CIS). Some people with CIS later develop relapsing-remitting MS, where symptoms come and go over time.
Doctors have known for a while that low levels of vitamin D are linked to a higher risk of developing MS and increased disease activity. But past studies on vitamin D supplements have shown mixed results. Most earlier studies used vitamin D as an extra treatment alongside other medications.
The researchers in this new study wanted to see what would happen if vitamin D was used on its own, especially right after the first signs of MS appeared.
The study, called D-Lay MS, was a randomized, double-blind, placebo-controlled trial—meaning neither the patients nor the doctors knew who was getting the real treatment and who was getting a fake one (placebo).
A total of 316 people between the ages of 18 and 55 took part. They had to have experienced their first MS-like symptoms within the past 90 days and have lower-than-normal vitamin D levels. Their MRI scans also had to show signs that suggested possible future MS.
Participants were split into two groups. One group took 100,000 IU of vitamin D (cholecalciferol) by mouth every two weeks for two years. The other group took a placebo on the same schedule. The main thing researchers measured was whether the participants had a new relapse or developed new lesions in the brain or spine on MRI.
The results were promising. Only about 60% of people in the vitamin D group experienced new disease activity, compared to 74% in the placebo group. Those taking vitamin D also went longer before any new disease activity appeared—a median of 432 days compared to 224 days in the placebo group.
MRI scans showed that the vitamin D group had fewer signs of worsening MS. They had:
- Fewer new or growing lesions in the brain (46.2% vs. 59.2%)
- Fewer contrast-enhancing lesions, which show active inflammation (18.6% vs. 34.0%)
- Less overall MRI activity compared to those on the placebo
The vitamin D treatment was also well tolerated and did not lead to major safety concerns.
Review and Analysis
This study provides strong evidence that high-dose vitamin D might help slow down disease activity in people who have recently shown early signs of MS. It’s especially important because the treatment is low-cost, easy to take, and has relatively few side effects.
The findings also challenge the idea that vitamin D should only be used as an “add-on” therapy. In this case, vitamin D alone showed meaningful benefits in delaying MS progression. This could be particularly helpful in parts of the world where access to standard MS medications is limited or unaffordable.
However, this was a carefully selected group of patients—people who were recently diagnosed and hadn’t yet started other MS treatments. That means the results might not apply to everyone with MS. Also, while the study showed fewer signs of disease activity, it didn’t measure long-term disability, so we don’t yet know if the benefits will last.
Still, the research points to the potential of high-dose vitamin D as a helpful tool in early MS care. The authors suggest future trials should test vitamin D as an add-on to standard treatments, especially in people with severe vitamin D deficiency at the start.
In summary, vitamin D could become a useful and affordable option for managing early MS—especially in the early days after symptoms appear, when quick action might help change the course of the disease.
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The research findings can be found in JAMA.
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