Vitamin D & COVID-19

Vitamin D & COVID-19

Is it necessary and does the Government recommendation of 400iu/day go far enough?

It’s long been known that vitamin D is linked with healthy immune function. Those of us with low levels of vitamin D are more likely to suffer from infections and viruses, and poor vitamin D status increases the likelihood of developing autoimmune diseases. As the COVID-19 pandemic has unfolded, it has emerged that there is a connection between vitamin D status and our ability to fight off the virus and reduce complications from the disease.


Early on, some of the studies showing a positive association between vitamin D intake and management of COVID-19 that made headlines were not deemed robust enough to be judged conclusive, but as the pandemic has unfolded and more data has been gathered, there is now enough of a body of evidence to conclude that vitamin D does benefit patients and reduces risk amongst the general population. Some of the results are quite remarkable - in one recently reported study led at the University of Cantabria, researchers found that 82% of coronavirus patients out of 216 tested had a vitamin D deficiency, compared to a control group where 47% of people who didn't have the virus were deficient.

Based on historic understanding of the importance of vitamin D to immune function and now the emergence of further clinical study in COVID-19 patients, the Government - having already advised in the autumn that everyone should be taking vitamin D throughout the winter months -  went on to announce that it would be providing free vitamin D to the elderly and vulnerable as part of their strategy in the fight against COVID-19.

What is vitamin D and why do we need to consider supplementation?

Vitamin D isn’t actually a vitamin - in fact, it’s actually a hormone that is critical to immune function. Having adequate levels, allows the innate immune system to function at its best. Our immune cells have ‘receptors’ for vitamin D, which means vitamin D can communicate with cells of the immune system and pass on messages. Vitamin D is thought to help boost immunity where needed, but also regulate the immune system. This means it could also help prevent over-activation that can lead to problems such as allergies and autoimmune disease, such as rheumatoid arthritis, psoriasis and MS. Additionally, It also helps produce anti-bacterial chemicals in the body to help keep germs at bay.

It’s often referred to as the ‘sunshine vitamin’, as the human body creates it in response to exposure to sunlight. Deficiency is common in the UK, as we don’t get much sun exposure, especially throughout the Winter months. Additionally, some people are naturally more prone to vitamin D deficiency, including those with certain health conditions, people who don’t spend much time outdoors, those who usually wear clothes that cover a lot of the skin (all of us in winter!), night-shift workers, and people with darker skin tones. The common use of sunblock - important in the prevention of skin cancer and ageing - may have compounded the issue of widespread deficiency.

We now know that complications of coronavirus can occur as a result of an uncontrolled inflammatory response known as a ‘cytokine storm’ - hence the effectiveness of the anti-inflammatory steroid drug, Dexamethosone. One of the reason’s it’s thought that having optimal vitamin D levels is so crucial, is that it increases levels of immune cells circulating in the blood, and can help to prevent uncontrolled inflammation - the very thing that leads to serious deterioration in COVID patients.

What sort of doses are we talking about? Is the RDA of 400iu enough?

In contrast to the RDA value of 400iu recommended by the NHS, many researchers have long advised that a dose of around 2000iu taken daily is an optimal amount for a healthy adult to take regularly. When it comes to optimising our defenses against COVID-19, researchers suggest between 2000iu and 4000iu might be best, but we don’t have conclusive data yet. In some studies of the effect of vitamin D supplementation on patients already admitted into hospital with complications, ultra-high doses of tens of thousands of IU were used in treatment - not something that should ever be done without medical supervision, or long term.

Dr Gareth Davies, (PhD Medical Physics, Imperial College, London), member of a group of researchers and doctors forming an international alliance aimed at encouraging governments to increase recommendations for vitamin D intake to 4,000 IU/day, to help beat COVID-19, has been vocal in the media about the need for the current 400iu recommendation to be significantly increased.

The recommended amount of 400iu is based on the EU Nutrient Reference Value (NRV), formerly known as the Recommended Daily Allowance (RDA), but these reference values are the amounts needed to prevent a deficiency, not to optimise health. Dr Davies disagrees with the current NHS recommendations of 400iu/day, stating that it doesn’t offer immune protection against infection and disease - something that many other researchers specialising in vitamin D have long believed, even before COVID.

Historically, experts have argued that 1000-4000iu is an optimal daily amount for most adults, with the majority of the research concluding that 2000iu is an ideal dose for most adults to take without risk of complications associated with excess vitamin D intake - namely a condition called hypercalcaemia, a condition where excess calcium circulating in the blood can cause damage to organs.

It’s worth noting that the EFSA (European Food Safety Authority) guidelines for the Tolerable Upper Intake level of Vitamin D for adults is 4000iu, so it may be prudent to stick to 2000iu per day on an ongoing basis, until wider information and more research comes through on doses required to help support the body fight COVID-19 infection and reduce risk of complications.

As well as dosing, the form of supplemental vitamin D counts. There are two types commercially available - D3 and D2. Vitamin D3 is a higher quality and much more absorbable form, so always check the ingredients list of any multivitamin or immune complex you take, to make sure you’re using the best.

Finally, Vitamin D supplementation takes time to take effect. If you were hoping to start taking vitamin D with the idea of it optimising your immune function straight away, you’ll be disappointed. It takes 2 to 3 months for blood levels of vitamin D to fully stabilise after boosting intake, so if you’re not already supplementing, the sooner you start, the better.

Inessa Advanced Daily Multivitamin contains 2000iu of highly absorbable vegan vitamin D3 per tablet, along with optimal doses of zinc and selenium, all of which play a role in supporting immune function.

If you enjoyed reading this article, you might like The science behind Inessa Multivitamins

Post author

Aliza Marogy

Nutritional Therapist, ND & Founder of Inessa