April 4, 2025, 8:49 am | Read time: 6 minutes
Numbness, tingling hands, or eye problems — subtle symptoms that occur from time to time and are hardly noticed at first. But then you get the news: it could be multiple sclerosis! A disease that occurs in episodes and can progress very differently from person to person. At the beginning, symptoms can even disappear completely — until the next relapse. Nobody knows how severe it will be and what symptoms will remain. According to a recent study, vitamin D may play a key role in influencing the course of the disease to a certain extent.
Vitamin D has long attracted attention in connection with multiple sclerosis. Researchers suspect that an adequate supply or the opposite — a deficiency — could play a role in the risk of developing the disease.1 A study has now provided evidence that vitamin D could be important not only as part of prevention but also in the early stages of the onset of MS. Would supplementation be able to slow down the progression of the disease or even stop it?
Overview
The Clinically Isolated Syndrome
In the Université de Montpellier study, researchers focused on a very specific stage of MS: clinically isolated syndrome. In simple terms, this is the first episode with lesions that are detectable in the brain, which — if followed by a second episode — leads to an official diagnosis of multiple sclerosis. Strictly speaking, the isolated syndrome is, therefore, a precursor to the actual disease.2
Vitamin D as a Therapy Against MS?
Early intervention could be crucial at this stage, both to slow down the acute episode and potentially to reduce the risk of a second episode and the progression to chronic MS, which often involves more severe episodes and the risk of permanent damage. As vitamin D deficiency is considered a potential risk factor for MS, the scientists investigated the effect of treatment with high doses of vitamin D.
While earlier studies investigated the use of vitamin D in addition to standard therapies, scientists are now investigating the use of vitamin D alone.3
Standard MS Therapies
Standard MS therapies often include acute relapse therapy with anti-inflammatory drugs. In addition, immunoprophylactic therapies can be added during the course of the disease to prevent further relapses with permanent consequences, including disability.4
Course of the Study
The study was conducted at 36 MS centers in France and lasted two years. Between July 2013 and December 2020, 316 patients between the ages of 18 and 55 were recruited for the study.
The inclusion criteria were:
- Presence of the aforementioned clinically isolated syndrome (CIS) — with a duration of less than 90 days
- No previous treatment for MS
- Serum vitamin D concentration of less than 100 nmol/L (75.0 to 150 nmol/L is considered a balanced vitamin D level).5 The study, therefore, included people with a healthy vitamin D supply as well as people with a deficiency.
- The presence of typical MRI findings for MS and the detection of certain indicators (lesions in the brain and spinal cord) for an increased risk of developing MS.
Participants were randomized in a 1:1 ratio: 163 received oral 100,000 I.U. of cholecalciferol (vitamin D) every two weeks, while 153 participants (control group) received a placebo, both for a duration of 24 months.
During the observation period of two years, the researchers determined the MS disease activity of the study participants, which was defined as relapse and/or new lesions on MRI.6
Effect of Vitamin D on Clinically Isolated Syndrome
The analysis was completed with 288 patients who participated in the study for the full two years. 60.3 percent of the vitamin D group suffered a relapse of MS or had new lesions on MRI. In the placebo group, this applied to 74.1 percent of participants. This corresponds to a significant risk reduction of 34 percent. In addition, the time to disease activity was significantly longer in the vitamin D group. In other words, it took longer until the next relapse.
However, there was no significant difference in clinical relapses alone: 17.9 percent in the vitamin D group vs. 21.8 percent with placebo. Clinical relapses are characterized by actual symptoms, whereas changes visible on MRI may not always be symptomatic. These MRI-visible changes can indicate inflammatory processes that progress without acute symptoms.
The most benefit from vitamin D supplementation was seen in participants who had a pre-existing deficiency, those with a BMI in the normal range, and individuals without spinal cord lesions at the study’s onset.7
Significance of the Results
The results show for the first time that high-dose vitamin D monotherapy can significantly reduce early disease activity in CIS — especially with regard to inflammatory processes that are only visible on MRI imaging. This early phase of an incipient MS disease is particularly relevant, as inflammatory processes are often still largely reversible at this stage.
It is noteworthy that these effects were observed without simultaneous immunomodulation — an indication of an independent, possibly immunoregulatory effect of vitamin D (cholecalciferol). Although the difference in clinical relapses remained insignificant, the MRI results indicate a reduction in inflammatory activity — an important marker for the prognosis of MS progression.
For patients with CIS or early MS, these findings suggest that vitamin D might serve as a supplementary or even initial treatment option, at least until the commencement of standard therapy. For physicians, the study provides a well-founded basis for decisions on the early use of high-dose supplementation in cases of vitamin D deficiency.
Classification of the Study and Possible Limitations
The strength of the study lies in its design: randomized, double-blind, placebo-controlled, and conducted with 288 participants in specialized centers. The adherence to the high dosage over two years also lends credibility to the study’s findings.
However, there are limitations: The study only examined the effect in untreated CIS patients, meaning the results may not be directly applicable to patients with established MS or those undergoing immunotherapy. In addition, the clinical effect in the case of relapses remained statistically inconspicuous — which leaves open the long-term relevance and influence on disability due to advanced MS.
A further point concerns the dosage: 100,000 IU every two weeks — which would be approx. 7000 IU daily if calculated over individual days — is very clearly above the DGE recommendation of 800 IU per day.8 Whether such a dosage is safe in the long term cannot be conclusively assessed from this study, even if no relevant side effects were observed.
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Conclusion
The findings of the French scientists underpin the indications from research that vitamin D is of great importance in connection with MS. And apparently not only because a deficiency increases the risk of developing the disease but also as part of a kind of initial therapy for incipient MS.
Additional research is necessary to give both doctors and patients confidence in the actual effects and safe application, such as the appropriate dosage. However, based on current knowledge, it cannot be denied that vitamin D should be considered in the context of MS diagnosis and treatment.