Hello from all of us at Sunlight Nutrition.

The days are getting shorter and darker meaning less glorious sunshine. At this time of year it’s important that we all start taking a vitamin D supplement again. We thought we would recap on the importance of this micronutrient and look at some up to date research regarding vitamin D and COVID-19.

Vitamin D

This is a fat soluble vitamin which we all need to protect our bones, teeth and muscles. Vitamin D is also considered to play an important role in the immune system.

Over the last 18 months Vitamin D has made the headlines and has been suggested to play a role in protecting from COVID-19. You may remember our blog post last year on the subject. You can remind yourself here: https://sunlightnutrition.co.uk/2020/12/10/vitamin-d-covid-19/.

So what’s the update since then?

The National Institute for Health and Care Excellence (NICE) published a guideline in December 2020 that’s continues to recommend that vitamin D supplements should not be offered solely to protect from or treat COVID-19.

They reiterated that everyone should consider taking a vitamin D supplement between October and March due to lack of sunlight. The panel advised that 400IU of vitamin D per day is enough to prevent vitamin D deficiency. They highlighted concern that taking daily high doses of vitamin D can lead to vitamin D toxicity which is dangerous and can cause a build-up of calcium in the body and can damage the bones, kidneys and heart. They acknowledged that individuals over 11 years old can likely tolerate higher doses but advise that a dose of 4000IU per day should not be exceeded and those taking vitamin D at these levels should be monitored, especially in cases of renal impairment (1).

The panel were presented with studies and evidence on using Vitamin D supplements to prevent COVID-19 infection. They also reviewed evidence on vitamin D status and association of this with development and severity COVID-19. Ultimately, they found no evidence to suggest vitamin D supplements protect against COVID-19. They did however agree that low levels of vitamin D were associated with more severe outcomes from COVID-19 but this does not mean that low levels of vitamin D cause more severe outcomes (1). Remember, umbrellas are associated with rain, but they do not cause rain.

What could the association mean then?

Firstly, lots of the risk factors for severe COVID-19 are the same as the risk factors for low vitamin D levels. Additionally, vitamin D levels fall during an inflammatory response, which often occurs with illness from COVID-19. This means that it’s hard to say if low vitamin D causes more severe outcomes or if COVID-19 and more severe outcomes cause low vitamin D levels (1).

The panel were presented with evidence from a study carried out in Spain using high doses of vitamin D to treat COVID-19. They raised some concerns with the quality of the evidence and based on the direct evidence available, they agreed that at present there is not enough evidence to recommend using vitamin D to treat COVID 19. They recommend that high-quality randomised controlled trials are needed (1).

What about vitamin D and respiratory tract infections?

The Scientific Advisory Committee on Nutrition (SACN) published an updated review of Vitamin D and acute respiratory tract infections (ARTI). From reviewing available evidence SACN concluded that overall, there may be some benefit from daily low dose (400-1000U) of vitamin D in reducing the risk of ARTI but any potential benefit would be small. They also recommended that it is unknown if reported benefits would be equal in populations from black, Asian and minority ethnic groups and those with BMI over 25kg/m2, as data was not available for these populations. They advised that this topic shall remain under urgent review (2). NICE agree that this should be regularly reviewed and reiterate that there is not enough evidence to recommend a vitamin D supplement solely for preventing COVID 19 (1).

The ZOE Study

The COVID symptom study was started by scientists and doctors at hospitals and Universities including Harvard and Kings College London with research being led by Prof. Tim Spector. The research aims to better understand COVID, its symptoms and understand more about the COVID vaccine. Over 4.5million people have already contributed to the research.

By downloading the app you can contribute to the study, whether you’ve had COVID-19 or not by giving details of any previous tests, vaccines and any associated symptoms. The website also includes lots of in depth evidence based information around COVID-19, treatment, vaccines and emerging research.

The website also includes lots of information about vitamin D and COVID-19.  It is important to note this is an observational study using self-reported information and although it has highlighted some associations between taking some nutritional supplements and lower risk of COVID-19, this is weak quality evidence and therefore there are currently no new recommendations for taking any supplements, including vitamin D to protect from COVID-19. Experts associated with the ZOE study recommend to continue following current recommendations for vitamin D from Public Health England for healthy bones, muscles and teeth.

Food sources of Vitamin D

Although it is difficult to get all the vitamin D we need from food, good food sources include oily fish (salmon, mackerel, sardines), red meat, liver, mushrooms, egg yolks and foods which have been fortified with vitamin D (some spreads, cereals, dairy products).

In conclusion

There has been no further convincing evidence for using vitamin D to prevent or treat COVID-19. There is a small amount of evidence to suggest that taking a daily low dose of vitamin D (400-1000IU) may reduce risk of ARTI. NICE, SACN and ZOE study recommend to continue to take 400IU of vitamin D from October through to March to support healthy bones, muscles and teeth, overall immune system and reduce risk of vitamin D deficiency.


  1. National Institute for Health and Care Excellence (2020) ‘COVID-19 rapid guideline: vitamin D. Available at: https://www.nice.org.uk/guidance/ng187/resources/covid19-rapid-guideline-vitamin-d-pdf-66142026720709
  2. Scientific Advisory Committee on Nutrition (2020) ‘Update of rapid review: Vitamin D and acute respiratory infections’ Available at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/945179/SACN_December2020_VitaminD_AcuteRespiratoryTractInfections.pdf
  3. COVID ZOE Symptom Study (2021) ‘Does Vitamin D protect against COVID-19’. Available at: https://covid.joinzoe.com/post/does-vitamin-d-protect-against-covid-19#:~:text=Last%20year%2C%20ZOE%20and%20King%E2%80%99s%20College%20London%20did,provide%20conclusive%20results%20in%20favour%20of%20vitamin%20D.%C2%A0