New research sheds light on the vitamin D puzzle

We know there's a link between low vitamin D levels and a higher risk of developing MS. But previous research has found that vitamin D supplements don’t seem to be effective as a treatment for MS.

In a recent study, researchers looked at the use of high-dose vitamin D in people with clinically isolated syndrome (CIS) which can be an early sign of MS.

What did the researchers do?

303 people with CIS took part in the D-Lay MS study between 2013 and 2023. Half of the participants took high-dose vitamin D. The other half took a placebo (dummy drug).

The diagnostic criteria for MS were updated during the study. This meant that 247 participants who were originally diagnosed with CIS would now be diagnosed with relapsing remitting MS.

Researchers wanted to see if vitamin D supplementation had an impact on relapses or new lesions on an MRI scan.

What did they find?

Researchers found that:

• participants who took high-dose vitamin D had a 34% lower risk of relapses or new lesions, compared to the placebo
• relapses and new lesions were seen less frequently in people who took high-dose vitamin D (60.3% vs 74.1% of participants on the placebo)
• people who took high-dose vitamin D had a longer average time to a relapse or new lesions (432 days, vs 224 days in the placebo group).

Further analysis showed the same benefits from vitamin D supplementation in people who would have been diagnosed with MS under the newer diagnostic criteria.

How does this fit with other research?

The VIDAMS study found that vitamin D supplementation didn’t have an effect on relapses or new lesions in people with relapsing remitting MS. And the PrevANZ study found that supplementation with vitamin D didn’t prevent someone’s progression from CIS to an MS diagnosis.

So the results of D-Lay MS seem to contrast with what we’ve learned from other trials. This could be because of differences in who took part in the trial. Or how the trials were designed.

These differences were explored in another recent paper. Including:

• Participants in the French D-Lay MS study had lower starting levels of vitamin D than people in Australia and New Zealand who took part in PrevANZ. So supplementation might have more of an impact on people who are deficient in vitamin D to begin with.

• People in PrevANZ took part in the trial for 1 year. While people in D-Lay MS stayed in the trial for 2 years. The longer D-Lay study may have given more time for the effects of the treatment to be observed.

D-Lay MS and PrevANZ looked at the impact of vitamin D in CIS. Recent updates to the diagnostic criteria for MS have enabled earlier diagnosis and treatment. We know that early treatment improves long-term health and wellbeing for people with MS. So it’s unlikely that we will see further trials that use a placebo (dummy drug) in CIS, which could delay the start of MS treatment.

What does this mean for people with MS?

Dr Emma Gray, our Director of Research, said:

The results of this study suggest that vitamin D supplementation may have some benefit for some people with early MS. But it’s important to note that the dose of vitamin D tested in the D-Lay MS study was much higher than the recommended dose. And participants were monitored closely for safety purposes.

We know that vitamin D is important in other ways, including bone health. If you are concerned about your vitamin D levels, we recommend you speak to your health care professional to see what supplementation dose is right for you.