ECTRIMS 2025: High-dose Vitamin D reduces MS activity, study finds
Results indicate supplementation doses don't need to be tailored to each patient
Increasing blood vitamin D levels with high-dose supplementation can significantly reduce the risk of new disease activity in people with clinically isolated syndrome (CIS), or those who experienced a first episode of symptoms suggestive of multiple sclerosis (MS).
That’s according to new data from the D-Lay-MS Phase 3 trial (NCT01817166), which tested whether a high dose of cholecalciferol, a form of vitamin D, was safe and could delay the progression from CIS to clinically definite MS.
The recent analysis also found that individual factors such as weight and body mass index (BMI), a measure of body fat based on weight and height, had only a weak influence on vitamin D changes, indicating that doses do not need to be tailored to each patient.
The new findings were shared by Manon Rival, MD, a neurologist at the Nîmes University Hospital Center in France, at the 41st Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS), held recently in Barcelona, Spain, and online.
While expert guidelines are now needed to define the ideal vitamin D dose and the patients most likely to benefit, Rival noted that vitamin D supplementation may potentially be used as “an add-on therapy or maybe for patients [who] didn’t support first-line therapies.”
Rival’s poster was titled “Effects of vitamin D supplementation on disease activity after a clinically isolated syndrome according to plasma vitamin D levels: ancillary analysis of the D-lay MS randomised controlled trial.”
Vitamin D plays vital role in immune system regulation
Vitamin D plays an important role in regulating the immune system and can influence the activity of immune cells involved in MS. Low vitamin D levels are a well-established risk factor for MS, but whether vitamin D supplementation can reduce disease activity has so far remained unclear.
To address this question, the D-Lay-MS study was designed to test whether supplementation with high-dose cholecalciferol — 100,000 IU every two weeks — was better than a placebo at preventing new disease activity in people with CIS. Cholecalciferol is a form of vitamin D produced in the skin upon exposure to sunlight, though it can also be found in certain foods and supplements.
The trial enrolled 303 adults who had experienced a first episode of MS-like symptoms within the past three months and were not taking any disease-modifying therapy. All were initially diagnosed with CIS using the 2010 McDonald Criteria, a set of diagnostic guidelines for MS. However, under the 2024 update, almost all would now be classified as having relapsing-remitting MS (RRMS).
Earlier results from the trial showed that vitamin D supplementation significantly delayed the onset of new disease activity (432 days vs. 224 days) and lowered the overall risk by 34% compared with a placebo. This effect was mainly driven by a delay in MRI activity, as the proportion of patients experiencing relapses over the two-year trial did not differ between groups.
Treatment group saw substantial increase in vitamin D levels after 3 months
At ECTRIMS, Rival presented data examining the impact of blood vitamin D levels on disease activity. The analysis included 266 people (about 85% of the overall study group), 88% of whom would meet the criteria for an RRMS diagnosis under the 2017 McDonald Criteria.
At enrollment, or baseline, there were no significant differences in vitamin D levels between the treatment and placebo groups. However, after three months of supplementation, the treatment group saw a substantial increase in vitamin D levels (by 94 nanomoles per liter), while levels in the control group remained unchanged.
The researchers also observed a weak negative association between vitamin D increases and participants’ weight and BMI, meaning that heavier individuals generally experienced smaller rises in vitamin D levels. Still, due to the excellent safety profile of high-dose supplementation, the team concluded that adjusting doses for individual patients is not necessary.
When the whole study population was examined, increases in vitamin D levels at three months were significantly associated with a lower risk of disease activity over two years, with each 100 nanomole-per-liter rise being linked to a 42% reduction in risk.
Within the treatment group, however, vitamin D levels at baseline or after three months did not distinguish patients who went on to experience disease activity from those who did not.
Rival emphasized that “it would be better to have other studies” before this high-dose supplementation could be routinely recommended, although it may be “quite difficult to have funding for this type of study.”
Meanwhile, Rival said she and her team plan to collaborate with other European experts under a consortium to develop consensus guidelines for vitamin D supplementation in people with MS.
Note: The Multiple Sclerosis News Today team is providing live coverage of the 41st Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) Sept. 24-26. Go here to see the latest stories from the conference.
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