Vitamin D back in the news – could ‘The Sunshine Vitamin’ prevent colds and flu?

“More than 3 million people across the UK could stave off infections such as colds or flu every year through taking Vitamin D supplements”, ran the headline of The Independent last Thursday. Indeed, vitamin D was dominating the headlines towards the end of last week across all media platforms, and not for the first time. And with 70% of the population suffering from at least one acute respiratory (such as a cold or flu) infection every year, could this latest claim be music to the ears of the UK population?

In this week’s article we take a closer look at the research and scientific mechanisms behind this latest research, as well as providing a recap on why vitamin D consumption is so important.

What is Vitamin D?

Vitamin D is known as ‘The Sunshine Vitamin’. This is because sunlight is necessary for the synthesis of vitamin D in the skin and those lacking in sunlight are at high risk of deficiency.

Vitamin D is not found in abundance naturally in foods. So simply put, not enough sunshine means not enough vitamin D, and hence issues with widespread deficiency in the UK particularly in areas such as parts of Scotland that get even less sunshine. The amount of sunlight (UV) in our winter months is insufficient and over the winter we need to draw on our bodily reserves.

There are some foods rich in vitamin D, primarily oily fish and eggs however fish consumption is poor in this country and as the Vitamin D Mission note:

“Salmon and other oily fish are big in vitamin D, along with liver, eggs and fortified cereals. But because of the quantities needed it’s hard to get enough from diet alone.”

Why is Vitamin D so important?

As noted on the Vitamin D Council website, “Vitamin D is important for good overall health and strong and healthy bones. It’s also an important factor in making sure your muscles, heart, lungs and brain work well and that your body can fight infection.”

Vitamin D has the following permitted health claims –

Vitamin D contributes to the:

  • normal absorption/utilisation of calcium and phosphorus
  • normal blood calcium levels
  • maintenance of normal bones and teeth
  • maintenance of normal muscle function
  • normal function of the immune system
  • process of cell division and
  • vitamin D is needed for normal growth and development of bone in children

The latest research

Certainly not for the first time, vitamin D has found itself right at the forefront of the media spotlight in the last week with new research from an NHS-backed study indicating that ‘daily vitamin D supplements would prevent more than three million people a year falling ill with a cold or similar infection’.

One of the researchers suggested that, “assuming a UK population of 65 million, and that 70% have at least one acute respiratory infection each year, then daily or weekly vitamin D supplements will mean 3.25 million fewer people would get at least one acute respiratory infection a year.”

But what is the exact science behind this claim?

Immune mechanisms

Vitamin D influences both innate and adaptive immune systems. The action of vitamin D is based on its binding to the Vitamin D Receptor (VDR), a nuclear receptor, which influences gene transcription patterns and which is expressed in the majority of immune cells including monocytes, B cells, T cells, neutrophils and Antigen Presenting Cells (APCs ie dendritic cells and macrophages). APCs link the innate and adaptive immune systems and present antigens to T cells.

Vitamin D – Innate immunity

Macrophages and monocytes are cells that reside in every tissue of the body. They engulf dead cells and pathogens and produce immune effector molecules. Upon tissue damage or infection, monocytes are rapidly sent to the tissue, where they differentiate into tissue macrophages. Through their ability to clear pathogens and instruct other immune cells, these cells have a central role in the immune system.

As part of the innate response, Vitamin D binding to VDR induces the production of antimicrobial peptides (cathelicidins) that are capable of killing pathogens or binding to endotoxin. During viral infections the lung epithelial cells are capable of converting inactive vitamin D to its active form leading to increased cathelicidin production. Supplementation of vitamin D in those who are deficient has been found to improve cathelicidin production and protection against infection. Vitamin D also upregulates the level of autophagy by monocytes.

Thus research has suggested that the active metabolite of vitamin D may enhance the antibacterial effects via enhancement of their [macrophages and monocytes] phagocytic and chemotaxis abilities”.

Vitamin D – Adaptive immunity

The adaptive immune system (or acquired immune system) responds slowly to an initial encounter with a pathogen but is able to create immunological memory so that subsequent responses are rapid. It includes T and B lymphocytes (white blood cells). Various types of T cells include those involved in killing the pathogen (T killer cells), regulating the immune response ie shutting it down once the threat has been neutralised (T regulatory cells), immunological memory cells (T memory cells) and others. B cells produce and secrete antibodies and also include a subset involved in immunological memory.

VDR expression increases significantly in activated B and T cells and influences 500 genes which are involved in the proliferation and differentiation of adaptive immunity cells. Importantly these genes also include ones that inhibit autoimmunity developing.

Vitamin D – Inflammatory response

An immune response upregulates inflammatory pathways including Nuclear Factor kappa B (NFkB). Vitamin D upregulates Inhibitor kappa B (IkB) which reduces NFkB signalling leading to a decrease in inflammatory cytokines. Thus as well as upregulating immunity vitamin D is important to suppress an ongoing inflammatory response.

Sources of Vitamin D

Vitamin D dietary sources include butter, eggs, oily fish and fortified foods – these sources provide only low levels of vitamin D – most is produced in the skin following sun exposure. In the UK, vitamin D can be synthesised in the skin between April and September, 10.00 am to 2.00 pm, on sunny days (i.e. without cloud cover). Production also depends on genetics, age, sunscreen, clothing, and skin colour. Although vitamin D cannot be synthesised during the winter at our latitude, it can be stored in the body. Levels are likely to be lowest around March.

With vitamin D supplementation now publicly being recommended, it is important to understand the difference between the most common forms of vitamin D, and which is the most suitable for supplementation.

Choosing the right form

Choosing the correct form of vitamin D to supplement with is just as important as supplementation itself, and although the new government guidelines now advise that everyone should take a vitamin D supplement, actual advice in this area has been lacking.

Vitamin D3 vs Vitamin D2

Vitamin D3 is the most bioavailable form of this nutrient and far preferable to Vitamin D2 to supplement with.

Vitamin D2 is also known as ergocalciferol and is commonly produced by plants in response to UV radiation. Some fortified foods contain vitamin D2 as an inexpensive addition, however it is not well absorbed or utilised by the body.

Vitamin D3 (also known as cholecalciferol) is the most bio effective and biologically active form of this nutrient and is found in humans and animals.

So when choosing a vitamin D supplement, you are looking for vitamin D3 and not vitamin D2. Where you wish to take a multivitamin and mineral that includes Vitamin D3 it is always important to select such a multi-formula with a nutrient content tailored for your age, gender, pre-existing medical conditions, or specifically for children where appropriate. If you are considering taking a vitamin D3 supplement and a multivitamin make sure that you assess the total combined dosage of the vitamin that you will be taking.

Relevant Cytoplan products

Our products contain vitamin D3, the most bioavailable form of this nutrient. Our vitamin D3 is from lichen and thus suitable for vegetarians and vegans

Vitamin D High potency

One tablet provides 62.5µg (2500i.u.) Vitamin D3 (Cholecalciferol) at 1250% of RDA. This can be taken alongside a multivitamin / mineral over the winter or all year round if needed

Vitamin D Low potency

At a lower potency of 15µg (600i.u), this Wholefood vitamin D3 is suitable for children and perfect to be taken alongside a suitable multivitamin.

CoQ10 Multi

Our most comprehensive Wholefood Multivitamin and mineral formula. At a dose of 1 per day this includes 20 mcg (800 iu) vitamin D as well as antioxidant CoQ10, Beta Glucan for immune support, and good all round vitamin & mineral levels. This formula now includes additional phytonutrients and Acerola Cherry rich in vitamin C and carotenoids.

Vitamin D Drops

Ideal for vegetarians and vegans this vitamin D supplement comes in the form of vitamin D3 Drops. Two drops provide 5 mcg (400 iu).

If you have any questions regarding the health topics that have been raised please don’t hesitate to get in touch with me (Clare) via e-mail (

Cytoplan Editorial Team: Clare Daley and Joseph Forsyth.

References are available upon request.

Last updated on 4th January 2018 by cytoffice


13 thoughts on “Vitamin D back in the news – could ‘The Sunshine Vitamin’ prevent colds and flu?

  1. Two questions:

    If a person based in Britain takes s week of winter sun in January, is this likely to mean the Vitsmin D levels will be Ok all year round

    Given all the variables age, skin colour, diet etc is the only way to know if you have enough vitamin D to have a blood tests. If so what should the target level be in say October to keep us going to March?



    1. Hello Nigel,

      Thank you for commenting on our blog.

      It is true that we can only know D levels by testing; but the majority of people in UK are estimated to be Vitamin D deficient. This is attributed to factors such as low exposure to sunlight due to low levels of sun, use of sun screens and lack of going outside as well as reduced intake of Vitamin D rich foods.

      A week of winter sun is useful but does not guarantee that Vitamin D levels are adequate throughout winter.

      It is recommended that serum Vitamin D levels are above 50ng/ml. The rate at which vitamin D levels decline over winter will depend on the individual, so it is difficult to estimate what levels should be in October. It is advisable to take a Vitamin D supplement over those winter months, however if you are concerned then vitamin D levels should be tested.

      Best regards,


    2. Nigel, great questions – all the answers can be found on the very comprehensive website They explain about how the amount of sun exposure varies according to skin types (darker skins need longer exposure), body type (obese people seem to have a problem with vitamin D synthesis), the fact that you can only synthesise a certain amount each day (eg about 30 minutes exposure creates as much vitamin D as a body can in a day) and the fact that we can’t store it long enough to last us all through the UK’s winter months.

      They also talk about optimum levels and the correct types of tests to have. Even if you had the best level possible in October, the half-life of vitamin D is about 30 days, so by March levels would have dropped significantly, which probably accounts for so many cold and flu symptoms in people around that type of year.

      Bear in mind that the UK and the US use different units for measuring blood serum levels which are easily converted. The Vitamin D council page also has information on that but it’s easy to get confused when looking online to check optimum levels. In Cytoplan’s reply to you, they recommend 50mg/ml as the minimum level for optimum health – in the UK that translates as 125 nmol/litre. (You’ll probably find that the NHS suggests that 70-80 nmol/litre is the best levels, but they always err on the lower side of things!)

      I would suggest having a look at the website as it’s difficult for anyone to advise in a general sense.

  2. You don’t mention the importance of taking K2 mk 7? Many supplements include this but I notice some of yours Don’. Could you explain please.

    1. Hi Janet,

      Thank you for your comment on our blog.

      We include vitamin K2 (MK-7) in many of our supplements – all our multi formulae, for example, which also include vitamin D. As you have noted, we have some supplements without vitamin K. This is because some people want a supplement without the vitamin K – eg people on anti-coagulant medication should not take more than 100 mcg of vitamin K per day, and if they were taking a multi plus extra vitamin D this could then go above this level. Vitamin K2 is important for helping to ensure that calcium is deposited in bones rather than soft tissue – here is a link to a previous blog that we have written on it.

      Many thanks,

      1. Thank you. I understand what you are saying. My concern is that unless this is made clear, people taking a vit D3 supplement who don’t take a mutivit including vit K MK 7 may not realise the importance of this fact. I spoke to someone recently who after reading an article about D3 was doing exactly that,

  3. Great article.

    However, whenever I discuss vitamin D supplementation online, I often get a whole load of people telling me that magnesium deficiency is the real cause of low vitamin D levels.

    I agree that we are all likely to be deficient in magnesium these days and have just had a look in your pdf booklet about magnesium, where there is one key sentence, “As mentioned above, magnesium also plays a part in the formation of several enzymes including those that activate Vitamin D.”

    I guess this is where these people are coming from – but they tell me that supplementing with magnesium automatically raises the body’s vitamin D levels so that more of it is produced from dietary sources as well as the sun, and that vitamin D supplements are not really necessary.

    It seems to me that the recent realisation that most of us are vitamin D deficient is not solely due to the avoidance of sun, the use of sunscreens, shorter lunchbreaks etc etc and that perhaps a significant reason might be the diminishing dietary levels of magnesium over the years?

    What do you think?

    PS For the record, I supplement myself with your vitamin D and magnesium products and recommend them to clients, friends and family – and everyone says they feel 100% better because of it!

    1. Dear Vanessa,

      Thanks for your question. yes, I am sure this is a factor in the widespread deficiency. However the biggest area of depletion is from lack of whole body sun exposure, as we had in ancestral times, and the reduction in Vitamin D3 consumed in the diet. But it is a situation that is indeed multifactorial.

      All the best,

  4. Hi, I currently take your multivitamin supplement… am I ok to take a vit d3 supplement (25ug) with this through the winter? Thanks

    1. Hi Sharene,

      Thank you for your question. Yes that is fine to take alongside one of our multivitamin and mineral supplements. There is a good level of vitamin D in our multivitamin/mineral products, for example, Foundation Formula 1 has 20 mcg per 2 tablet dose and CoQ10 Multi has 40 mcg per 2 capsule. Over the winter however some people may benefit from a higher dose for a few months and the dose you propose would be ok.

      All the best, Clare

  5. How much vit d and vit c do you recommend me to take? I have Epilepsy, osteoporosis and arthritis. I am also housebound and take herbal magnesium, copper, joint and muscle and b12.

    1. Hi Anne,

      Thank you for your question on our blog. It would be a good idea to have your vitamin D levels tested. Your GP can arrange for this or a home test is available from In the meantime I would suggest an all-round multivitamin and mineral – we have a product called Cyto Gold which contains 20 mcg of vitamin D plus some calcium as well as other vitamins and minerals. Plus our Bone Support product which contains additional vitamin D along with calcium, magnesium, isoflavones and vitamin K. Taking both Cytogold and Bone Support together would provide you with a daily intake of 50 mcg (2000 iu) of vitamin D.

      With regard to vitamin C, Cytogold contains a small amount of vitamin C (20 mg). You could take it alongside Wholefood Cherry C which contains 200 mg of vitamin C.

      You mention that you take copper – is there a particular reason for this? I would not advise taking this long-term as a single nutrient. It is included at an appropriate level in our multi supplements. Copper can interfere with absorption of other minerals and is undesirable at high levels.

      As you have epilepsy I would recommend that you check with your doctor before taking any supplements.

      Also we offer a free health questionnaire service – if you complete and return a health questionnaire we will send you some written diet and supplement recommendations – this is a free service.

      I hope this helps.

      All the best,

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