Vitamin D and MS
Researchers are working hard to fully understand the link between vitamin D and MS. And to test if vitamin D could be a treatment for MS.
The body needs vitamin D to help absorb different nutrients, in particular calcium. You may hear vitamin D referred to as the sunshine vitamin. That's because it’s produced in our skin in response to sunlight.
We get most of our vitamin D through sun exposure. But it’s also found in small amounts in oily fish, eggs, meat, milk and margarine. Some cereals and yoghurts are also ‘fortified’ with vitamin D.
Why has vitamin D been linked to MS?
We know MS is more common in countries further away from the equator. There are many possible reasons for this pattern. But researchers are particularly interested in the role that sunlight (and therefore vitamin D) could play in MS.
In 2015 scientists demonstrated a clear link between low vitamin D and MS. They found that people who naturally had lower levels of vitamin D (because of their genetics) were more likely to develop MS. Researchers in Oxford have also discovered that vitamin D could affect the way a gene linked to MS behaves. They showed that when vitamin D was present, the gene was more active. This groundbreaking research could help us understand more about the role vitamin D plays in developing MS.
There's currently no evidence that high vitamin D levels reduce the risk of developing MS.
Find out more about Vitamin D
While there are still a lot of unanswered questions, the evidence is growing that there is a protective role for vitamin D in MS. Researchers have looked to see if low levels of vitamin D at different stages of development can affect someone's future risk of MS.
Vitamin D during pregnancy
In 2016 scientists found that children born with very low levels of vitamin D were more likely to develop MS in later life.
The study didn't find that increasing levels of vitamin D beyond the recommended levels reduced the risk of developing the condition though. This adds to previous research linking the month you were born in and the risk of developing MS. In 2016 a large and very detailed study was carried out, involving over 21,000 people with MS. Researchers found that people born in November were less likely to develop MS than those born in April.
The link between month of birth and risk of MS suggests some environmental risk factors for MS could act before birth.
Vitamin D in childhood
Research shows a lack of vitamin D in early childhood might increase the risk of developing MS later in life. Studies show people who've moved to a new country during childhood adopt the risk of the country they move to. But if people migrate later in life (in their twenties or later), they keep the risk profile of their country of birth.
A study from Sweden in 2015 also found a link between teenagers with early onset MS and low exposure to summer sun during their teenage years.
These studies indicate there may be an important role for vitamin D and other environmental factors in MS during childhood and early development.
Genetics
In 2015 scientists demonstrated a clear link between low vitamin D and MS. They found that people who naturally had lower levels of vitamin D (because of their genetics) were more likely to develop MS.
Researchers in Oxford have also discovered that vitamin D could affect the way a gene linked to MS behaves. They showed that when vitamin D was present, the gene was more active. This groundbreaking research could help us understand more about the role vitamin D plays in developing MS.
There's some evidence that lower levels of vitamin D are associated with higher relapse rates in MS. One study found that people with higher levels of vitamin D (above 50 nmol/l) were less likely to have relapses or new MRI lesions after five years.
Low levels of vitamin D have also been linked to an increased risk of disability progression and declining cognitive function for people with clinically isolated syndrome (CIS). But we don’t know if taking vitamin D supplements will have an effect on MS progression.
A number of studies have investigated whether vitamin D could be used to treat MS, with mixed results.
Latest research
In 2025, results from a trial suggested that high doses of vitamin D could be beneficial for people with early MS. Researchers found it lowered the risk of relapses or new lesions. This has contradicted previous research to date.
In 2023, a trial in the United States compared a low or high daily dose of vitamin D. The scientists found no difference in the number of participants experiencing a relapse when comparing the low and high dose of vitamin D. They also didn’t find a difference in the number of lesions or brain shrinkage on MRI scans.
These findings support several smaller, shorter studies also showing no effect of vitamin D supplements on the number of relapses.
But right now we still don’t have answers to some key questions, including:
- Do we need a different dose of vitamin D?
- Is it possible that only some people with MS benefit from vitamin D supplements?
Earlier research
A 2015 study found that high dose vitamin D could affect the immune system. The participants took 10,400 international units (IU) of vitamin every day for six month. This reduced the number of certain immune cells known to cause damage in MS. The trial involved 40 people with relapsing MS, but didn't test if vitamin D reduced relapses or slowed progression.
In 2015, scientists at our Cambridge Centre for Myelin Repair revealed a role for vitamin D in promoting myelin repair. They found that adding vitamin D boosted the number of myelin-making cells present in the brain by 80% in rats. The vitamin D receptor protein pairs with an existing protein already known to be involved in myelin repair, called RXR gamma.
In July 2016 the UK Government recommended that everyone take vitamin D supplements to promote bone health (10 micrograms/400 IU per day if you're older than one). This includes women who are pregnant or breastfeeding but wasn't specific to people with MS.
Some neurologists suggest people with MS should take higher doses than other people, all year round.
If you’re worried about your vitamin D levels, ask your MS team about getting a blood test. And speak to your MS team before taking high doses. Too much vitamin D could cause serious health problems.
- The European Food Safety Authority suggest that adults should not exceed 4000 IU (100 micrograms) per day.
- The NHS also recommends not exceeding 4000 IU (100 micrograms) of vitamin D daily, as it could be harmful to health.
Read our interview about vitamin D with expert neurologist Professor Ruth Dobson
Testing the benefits of vitamin D supplements is one of our top 10 research priorities. Better understanding how vitamin D is involved in MS could also help us develop new treatments.
We’ve funded several projects involving vitamin D. In 2021 a study by Dr Ruth Dobson found people with MS had higher levels of vitamin D than people without MS, because they were more likely to take a supplement.
The study gave us valuable insight into the vitamin D levels of the UK MS community which can be used to help design future studies.
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