Vitamin D

Evidence is growing for a protective role of vitamin D in MS, and it remains an active area of research with a number of unanswered questions. Without these answers, we don’t know whether taking vitamin D supplements could be a safe and effective strategy in the management of MS.

What is vitamin D?

Vitamin D is required by the body to help absorb different nutrients, in particular calcium. It can be made by the skin in response to UVB radiation from sunlight so is sometimes referred to as the ‘sunshine vitamin’.

While the majority is generated through sun exposure, vitamin D is also found in small amounts in oily fish, eggs, meat, milk, margarine and some cereals and yoghurts are ‘fortified’ with vitamin D.

A lack of vitamin D during childhood can cause rickets, and in adulthood can cause bone weakness.

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What is the link to MS?

Research has shown MS is more common in countries further away from the equator. As these countries also have less sunshine, this may influence the levels of vitamin D in these populations. This has led researchers to investigate a possible link between levels of vitamin D and MS.

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Vitamin D and MS - what do we know?

Understanding the link between vitamin D and MS is the subject of many researchers work and while there are still a lot of unanswered questions, we are learning more and more about the interaction.


In 1987, researchers started to investigate the link between the month you were born in and the risk of developing MS. Since then, lots of studies have tried to unravel this connection, with mixed results. This is because it’s difficult to account for all the other factors and because we need to study a large number of people to clearly see an effect.

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.
We don’t have all the answers yet, but researchers have suggested that seasonal differences in vitamin D levels could be one factor that plays a role.


Research shows a lack of vitamin D in early childhood or before birth 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 showed younger-age onset of MS was significantly associated with low exposure to summer sun during the 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 2009, researchers in Oxford published some groundbreaking research identifying a link between vitamin D and a gene known to be associated with MS. They showed that when vitamin D was present the gene was more active.

This was the first piece of research in MS to show an environmental factor may change the way a gene behaves. It could help us understand more about the interaction between vitamin D and somebody’s risk of MS.

In 2015 scientists demonstrated a clear link between low vitamin D and MS. Their research suggested that people who are genetically predisposed to having low vitamin D levels are more likely to develop MS.

As a treatment

There have been a number of studies which have tried to determine if taking vitamin D supplements could be used to treat the symptoms of MS. However, these studies

  • use different doses and forms of the vitamin
  • are often not carried out to a reliable standard

There is still not enough evidence to tell us whether vitamin D supplementation is an effective and also safe treatment for MS.

A Finnish study from 2012 looked at 100 people with relapsing remitting MS, 66 of whom were given vitamin D supplements in addition to their usual treatment with interferon beta. They found those who received vitamin D had fewer lesions after 12 months, however there was no difference in levels of disability or the number of relapses that people experienced.

Another 2012 study involved 69 people with MS from Norway, and compared the effect of vitamin D3 versus a placebo on relapse rates and disability levels. Although levels of vitamin D were found to be twice as high in the treatment group compared to those taking the placebo at the end of this two-year study, vitamin D had no effect on relapse rates or levels of disability.

A small US study in 2015 involving 40 people with relapsing remitting MS uncovered a role for high dose vitamin D in MS. People in the study took either 10,400 international units (IU) or 800 IU of vitamin D3 supplements daily for 6 months. Researchers found that the higher dose altered the immune system, by decreasing certain types of immune cells that are known to cause damage in MS. The same was not seen for people taking the lower dose.

The optimal level of vitamin D in the blood for people with MS has still to be determined.

Myelin repair

A piece of research from the Cambridge Centre for Myelin Repair in 2015 has shown vitamin D may have a role to play in myelin repair. Researchers identified the vitamin D receptor protein pairs with an existing protein already known to be involved in myelin repair, called the RXR gamma receptor. By adding vitamin D to brain cells where the proteins were present, they found the production rate of oligodendrocytes (myelin making cells) increased by 80%.

The focus of vitamin D research has been on a deficiency as a risk factor in MS. This work provides significant evidence that vitamin D could also be involved in the regeneration of myelin once the disease has started.

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A research priority

We’d now like to see more studies to understand whether taking vitamin D supplements could, in time, be an effective and safe treatment for people with MS. Investigating vitamin D supplementation as a disease modifying treatment is one of our top 10 research priorities.

Our Clinical Trials Network (CTN) has set up a working group which aims to address this issue for people with MS. The CTN is a diverse group of research experts, clinical trial methodologists and people with MS with individual expertise in different areas. They will work together to commission new research and will work towards developing a clinical trial investigating vitamin D supplements and MS.

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Should I be taking vitamin D supplements?

If you are worried about your vitamin D levels and think you might be deficient, you should discuss this with your health care professional.

In July 2016 the Government's Scientific Advisory Committee on Nutrition recommended that everyone in the UK take supplements to ensure they receive sufficient Vitamin D (10μg/400IU per day for those aged one years and above,  8.5-10μg/400IU per day for those under one). This includes pregnant and breastfeeding women and those at risk of vitamin D deficiency.

These recommendations are to ensure good musculoskeletal health and are not related to MS or other autoimmune conditions. They follow studies suggesting that most people in the UK are not getting sufficient vitamin D from diet and sunshine alone.

Many people with MS take vitamin D supplements, and while research so far points towards a role for vitamin D in MS, right now we don't know if taking supplements has benefits for people with MS. We don’t have concrete evidence to show taking supplements will reduce someone’s risk of developing MS or reduces symptoms or slows disease progression.

A recent review of vitamin D supplementation research published in the Lancet found supplementation brings no significant health benefits for healthy people.

Risks of taking too much vitamin D

As we see more research looking into the role of vitamin D in MS, it is easy to see why vitamin D supplements are attractive. There are risks associated with having too much vitamin D which should be taken into consideration.

One of the more serious side effects of taking too much vitamin D is hypercalcemia - the build-up of high levels of calcium in the blood. Complications associated with hypercalcemia include (but are not limited to): kidney and bile stones, bone pain, nausea, vomiting, psychological effects and abnormal heart rhythms.


  • The NHS recommends people taking vitamin D supplements not to exceed 1000IU (25 micrograms) per day.
  • The European Food Safety Authority suggest that adults should not exceed 4000 IU (100 micrograms) per day as there no evidence for safety above this level.

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Page last updated: 10 Nov 2016

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