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Vitamin D Choices booklet

What is vitamin D?

Vitamin D is sometimes called ‘the sunshine vitamin’ because it is the only vitamin that the human body can manufacture itself by absorbing sunlight. As with any vitamin, vitamin D is required for optimum health.

Vitamin D is important for a healthy immune system, brain development and function, and the cardiovascular system (heart and blood vessels). Vitamin D helps the body to absorb calcium and phosphorus – the building blocks for strong bones.

The most recognised way of producing vitamin D is through exposure to the sun. As the sun’s ultraviolet rays reach the skin, a chemical called 7-dehydrocholesterol is transformed into vitamin D by a photochemical reaction. The vitamin D is then stored in fat cells until needed by the body. Exposure to the sun can produce up to 90 per cent of the body’s daily vitamin D.

Many health professionals advise that people should get as much sun on the skin as possible with more in winter and less in summer (1). If you live in the northern hemisphere, the sun is only strong enough to deliver the amount you need between the months of April and October, from 10.00am to 3.00pm, if there is no cloud cover (2).

A good rule of thumb is, if your shadow is longer than you are tall, you are not making much vitamin D because the sun is low in the sky and therefore weaker.

Concerns about skin cancer means many people are covering their skin in the sun, either with clothing or creams containing a sun protection factor. So, chances are you are not producing sufficient vitamin D from sunlight.

Some people do not make sufficient vitamin D, even with the right amount of skin exposure.

  •  Elderly people have thinner skin than younger people and are unable to produce as much vitamin D
  • People with darker skin, for example people of African, African-Caribbean and South Asian origin, because their bodies are not able to make as much vitamin D
  •  Some medical conditions can affect the way the body metabolises vitamin D, and can lead to a reduced vitamin D level, for example people with coeliac disease, Crohn’s Disease, and some types of liver and kidney disease

As well as the body’s own production of vitamin D, it can also be obtained from a few foods, particularly animal sources such as oily fish (mackerel, salmon, sardines and tuna) and eggs. Vitamin D can also be found in fortified milk and cereal where the vitamin has been added to the food.

Because it is almost impossible to obtain all the vitamin D the body needs through food and sunlight alone, supplementation can be considered.

Vitamin D and general health

Before vitamin D’s importance in the absorption of calcium was understood, children with a lack of vitamin D, or a deficiency, would sometimes develop a condition called rickets where the bones in the legs would develop as soft and brittle. This was the first condition where the correlation with vitamin D and good health was made.

Vitamin D has also been linked to other conditions such as asthma, high blood pressure, depression, cancer, dementia, type 2 diabetes and autoimmune disorders such as multiple sclerosis (MS) and Crohn’s Disease.

A study of older people by Dr David Llewellyn at the University of Exeter Medical School, published in Neurology, followed 1,658 people for six years.

The researchers found that low vitamin D levels correlated to a one-in-five risk of developing dementia, whereas people with good levels of vitamin D had a one-in-ten risk (3).

Vitamin D and the link to MS

It is reported that the countries with the highest population of people with MS are located in the northern hemisphere, where sunlight levels can be very low in winter, for example Scotland.

It is widely believed that there are environmental and genetic factors associated with an overall higher risk of developing MS, although these are not absolutely understood.

There have been many studies looking at the effect of vitamin D in the likelihood of developing MS, or the effect of vitamin D on the symptoms of MS.

Much research has studied the link between vitamin D levels in a pregnant mother and the likelihood of her child developing MS in later life. A study in this subject was undertaken in 2004 of Canadian and British patients with MS and presented to The British Medical Journal (BMJ). The results showed that significantly fewer people with MS were born in November but a significantly higher number of people with MS were born in May. The study’s conclusion was: ‘Month of birth and risk of MS are associated, more so in familial cases, implying interactions between genes and environment that are related to climate. Such interactions may act during gestation or shortly after birth in individuals born in the northern countries studied’ (4).

Some research studies found a link between low vitamin D in pregnancy and a higher risk for the child to go on to develop MS, and some studies did not.

A study, looking at the effect of vitamin D in recovery from acute episodes of optic neuritis in people with MS, found a link between the severity of optic neuritis and vitamin D levels – people with higher levels of vitamin D had less severe episodes of optic neuritis. However there was no association with high vitamin D levels and a faster recovery from optic neuritis (5).

Another study into the vitamin D levels of people with MS, in relation to the number of relapses they experienced, showed the people in the study group with the highest vitamin D levels experienced the fewest number of relapses. The study recommended that more research be conducted with a larger study group to confirm these promising results (6).

Discussions between scientists to link low vitamin D levels to a higher risk of developing MS have been inconclusive.

There is no clear evidence to propose a definite correlation between the risk of MS and lack of vitamin D. Many more trials are underway to look at this interesting and vital vitamin.

In October 2014 the National Institute for Care Excellence (NICE) issued new guidelines for the clinical care of people with MS. In these guidelines NICE said that vitamin D should not be offered solely for the purpose of treating MS (7). But the guidelines also stated that more research was needed to determine if vitamin D slowed the progression of disability in people with secondary progressive MS because of the challenge to find ‘effective and well tolerated treatments for secondary progressive MS.’

What are the recommended doses for vitamin D supplementation?

For specific groups in the general population, the Department of Health recommends

  •  All pregnant and breastfeeding women take a daily supplement containing 10 micrograms (0.01mg) of vitamin D to ensure the mother’s requirements for vitamin D are met and to build adequate foetal stores for early infancy
  • All babies and young children aged six months to five years should take a daily supplement containing vitamin D in the form of vitamin drops to help them meet the requirement set for this age group of 7-8.5 micrograms (0.007-0.0085mg) of vitamin D a day
  • Babies fed with infant formula will not need vitamin drops until they are receiving less than 500ml (about a pint) of infant formula a day, as these products are fortified with vitamin D
  • Breastfed infants may need to receive drops containing vitamin D from one month of age if their mother has not taken vitamin D supplements throughout pregnancy
  • People aged 65 years and over and people not exposed to much sun should also take a daily supplement containing 10 micrograms (0.01mg) of vitamin D
  • You can buy single vitamin D supplements or vitamin drops containing vitamin D (for use by under-fives) at most pharmacies and supermarkets

New advice on vitamin D from Public Health England (PHE), based on recommendations from a government Scientific Advisory Committee on Nutrition (SACN) in 2016, said that adults and children over the age of one should have 10 micrograms (mcg) of vitamin D every day. This means that some people may want to consider taking a supplement.

You can ask your GP for a blood test to see if your vitamin D levels are in the normal range. If your levels are low, your GP may recommend taking a supplement.

The recommended daily intake in the UK for vitamin D for an adult is 400 International Units (IU).

In 2012, the European Food Safety Authority raised the Tolerable Upper Intake Levels (the levels that can be taken daily without causing harm) to 4000 IU (9).

Some authors think the recommendation of 4,000 IU is too low for people with MS

If you choose to take a vitamin D supplement, the best form is vitamin D3. This is the natural form of vitamin D made in the body when the skin is exposed to the sun. The form of which you take vitamin D3 is a personal choice, but there have been studies to determine whether an oil or a tablet delivers a better level of vitamin D (10).

One thing you may like to consider if you are a vegetarian, is that the capsules are often made of gelatine and are manufactured from the collagen of animal skin or bone.

Dr Jelenik’s Overcoming Multiple Sclerosis (OMS) programme recommends a daily dosage of vitamin D3 of 5,000 IU for people with MS, to be taken all year round (11). Their HOLISM study stated ‘OMS continues to recommend vitamin D supplements of around 5,000-10,000 IU a day, aiming for a blood level of at least 150nmol/L (60ng/mL)’ (12).

Blood level of 25 (OH) Vitamin D

Nano grams / millilitre (ng/ml) and Nano moles / Litre (nmol/L)

1 ng/ml = 2.5 nmol/L

30 ng/ml = 75 nmol/L

Dose: International Units and micrograms 

40 IU = 1 mcg

400 IU = 10 mcg

1000 IU = 25 mcg

50,000 IU = 1250 mcg or 1.25 mg (milligram)

The Vitamin D Council recommends adults should take 5,000 IU per day of vitamin D supplement.

For more information about safe levels, please read more on the Vitamin D Council’s website at

It is important to note that research into toxic levels of D3 is inconclusive. Please seek your GP’s or neurology specialist’s advice before starting a supplementation regime.

Do I need to take anything else along with vitamin D? 

The way vitamins and minerals work in the body is complicated, with some acting as ‘co-factors’ for each other – meaning that additional vitamins and minerals are needed alongside vitamin D to ensure its optimum activity.

The following may be co-factors for vitamin D, and could be considered as additional supplements

  • Vitamin A
  • Vitamin K
  • Boron
  • Magnesium
  • Zinc

Vitamin A

The body needs vitamin A for eye-health and maintaining healthy mucous membranes (the moist membranes in the body which line the nose and gut).

Most people will obtain sufficient vitamin A from diet alone – either as beta-carotene (in brightly coloured fruit and vegetables like carrots, mango, greens) or as retinol (from animal sources such as liver and dairy products).

If you have a balanced diet you should have the right levels of vitamin A.

It is important not to take more than the daily recommended amount of vitamin A in the form of retinol, because it is fat-soluble and therefore retained by the body. Beta-carotene is excreted in the urine.

High levels of vitamin A from retinol can be toxic, particularly in pregnant women. Before considering taking a supplement of Vitamin A, consult your GP.

Vitamin K

The body needs vitamin K for two important reasons: to make healthy bones and to facilitate blood clotting. Vitamin K works with vitamin D to make sure calcium is used in bone growth.

There are two types of vitamin K – K1 and K2

  • Vitamin K1 – can be found in leafy green vegetables like spinach, broccoli, kale and chard
  • Vitamin K2 – can be found in meat, particularly in animal organs such as liver, eggs and hard cheeses

Adults need very small amounts of this vitamin. If you have a balanced diet you should have the right levels of Vitamin K.

Vitamin K is fat-soluble so anything not used is stored in the liver for later use, therefore you don’t need to eat foods containing vitamin K every day.

There is not enough evidence to know what the effects might be from taking too much vitamin K, but the Department of Health advises that taking 1mg of vitamin K supplements daily is unlikely to do harm (13).

However, people on blood-thinning medications such as warfarin are advised not to take a vitamin K supplement.


Boron is a trace element and the body only needs a tiny amount of it for optimum health. It is believed to help the body use glucose, fats and other minerals in food. Boron is found in green leafy vegetables, nuts and fruit.

If you have a balanced diet you should have the right levels of boron. Taking 6mg or less of boron supplements a day is unlikely to cause any harm (13).


The body uses magnesium to release energy from food – 80 percent of the body’s enzymes use magnesium. Magnesium also helps to maintain a healthy heart and is needed to produce insulin. It is required to produce the neurotransmitters in the brain.

Magnesium is found in nuts, seeds and green vegetables.

Magnesium deficiency is rare because of its abundance in food, and because the kidney’s regulate its excretion.

If you have a balanced diet you should have the right levels of magnesium (13).


Like boron, zinc is a trace element and the body only needs a tiny amount of it for optimum health. It is believed to help the body use glucose, fats and other minerals in food. Zinc also helps with wound healing and making new cells and enzymes.

Zinc is found in meat, shellfish, dairy foods such as cheese and milk, bread and other cereals.

If you have a balanced diet you should have the right levels of zinc.

High doses of zinc, either from food or with a supplement can reduce the absorption of copper and can cause anaemia.

The Department of Health advise not to take more than 25mg of zinc supplements a day, unless advised to by a doctor (13).

This content is taken from the MS-UK Choices booklet. 

Visit the Choices booklet web page