Vitamin D

We're learning a lot about the role that vitamin D plays in MS. But we still don’t know if taking vitamin D supplements could help to manage 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.

Vitamin D basics

The body needs vitamin D to help absorb different nutrients, in particular calcium. You may hear vitamin D referred to as the sunshine vitamin. This is 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.

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Why has vitamin D been linked to MS?

We know that MS is more common in countries further away from the equator. Although there are many possible reasons  for this pattern, researchers have become particularly interested in the role that sunlight (and therefore vitamin D) could play in MS.

Researchers are now focusing on two key areas:

Can vitamin D treat MS?

We’re learning more and more about the importance of vitamin D in MS. But right now we still don’t have answers to some key questions, including:

  • Can vitamin D supplements help to prevent or treat MS?
  • Is vitamin D beneficial as a treatment for all types of MS?
  • What dose of vitamin D is needed?
  • What dose is safe?

What do we know so far?

There is 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.

Trial results

A number of studies have already been published, with mixed results. The trials have all been quite small and used different doses of vitamin D.

A 2015 study found that high dose vitamin D could affect the immune system. Taking 10,400 international units (IU) of vitamin every day for six months reduced the number of certain immune cells that are 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.

A Finnish study from 2012 found that vitamin D supplements reduced lesion development, as measured by MRI. However, the supplement didn’t reduce the number of relapses people experienced or slow progression. The trial involved 66 people with relapsing MS who were taking beta interferon

A 2012 Norwegian study also found that vitamin D did not reduce relapses or levels of disability. The trial involved 69 with relapsing MS.

We don’t yet know the best level of vitamin D for people with MS.

>> Read about our vitamin D research

Myelin repair

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.

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Should I be taking vitamin D supplements?

If you're worried about your vitamin D levels and think you might be deficient, you should discuss this with your health care professional. Making sure we’re not deficient in vitamin D is important for all of us, but right now we don't know if taking supplements could benefit people with MS.

>> Find out what we’re doing to address this.

General Government recommendations

In July 2016 the UK Government recommended that everyone take vitamin D supplements to promote bone health (10 micrograms/400IU per day if you're older than one). This includes women who are pregnant or breastfeeding.

This recommendation was not specfic for people with MS.

Risks of taking too much vitamin D

Taking too much vitamin D can lead to a build-up of high levels of calcium in the blood – a condition known as hypercalcemia. This can cause kidney and bile stones, bone pain, nausea, vomiting, psychological effects and abnormal heart rhythms.

How much is too much?

We don’t yet know the best level of vitamin D for people with MS. There are some government recommendations, but these are based on existing safety data and may not reflect a true upper limit.

  • The NHS recommends that adults should not take more than 1000IU (25 micrograms) vitamin D per day.
  • The European Food Safety Authority suggest that adults should not exceed 4000 IU (100 micrograms) per day.

>> Read about diet and MS

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Do vitamin D levels affect your risk of MS?

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.

>> Learn more about the causes 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. This suggests that vitamin D levels during pregnancy might affect a child’s future risk of MS. The study did not 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 who had been born in November were less likely to have developed MS than those born in April.

The link between month of birth and risk of MS suggests that some environmental risk factors for MS could act before birth.

>> Read more about vitamin D in pregnancy and MS

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 have 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 that there was 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.


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.

>>Read more about genetics research

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Our vitamin D research

Testing the benefits of vitamin D supplements is one of our top 10 research priorities. We’ve brought together leading researchers, people living with MS and health care professionals as part of our Clinical Trials Network (CTN).

Their goal is to develop a clinical trial to test the benefits of vitamin D as a disease modifying therapy for people with MS.

Before we can plan a trial, it’s important for us to know what’s already been done. That’s why we asked Professor Malcolm Macleod, an expert in neurological reviews, to provide an overview of what’s already known about the benefits of vitamin D supplements for people with MS.

Understanding the effects of vitamin D

We’re funding a number of research projects to help us better understand how vitamin D is involved in MS:

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Page last updated: 15 Feb 2018

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