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Scientists recommend a vitamin D intake of 4000 IU daily

4 min read

The link between vitamin D status and the incidence and severity of COVID-19 symptoms has been leading recent medical research during this pandemic.

You might be surprised to know it is not a new idea, interest in a potential role for vitamin D in the prevention or treatment of acute respiratory infections dates back to the 1930s, when cod liver oil was investigated as a way of reducing industrial absenteeism due to the common cold. 

Striking overlap between risk factors for severe COVID-19 and vitamin D deficiency

It's hard not to see the overlap between risk factors for severe COVID-19 and vitamin D deficiency, including obesity, older age, and Black or Asian ethnic origin as anything other than striking. This has led some researchers to hypothesise that vitamin D supplementation could hold promise as a significant aid in the global fight against COVID-19.

Scientists urge recommendations for vitamin D intake be increased to 4000 IU daily

Earlier this month reported on the formation of an alliance of researchers and doctors whose aim is to encourage governments to increase recommendations for vitamin D intake to 4000 IU daily. Underpinning this goal is the belief that taking vitamin D at much higher doses than the 400 IU the government currently recommends could reduce COVID-19 hospitalisations. 

Dr Gareth Davies, a member of the alliance and an independent coronovirus research scientist, suggests there is a lack of understanding of how vitamin D works within the body. Whilst it is referred to as a vitamin it is in fact a hormone essential to the functioning of both the innate and adaptive immune system. The group action therefore also involves a public awareness campaign as well as petitions and calls to MPs.

In June the UK government ordered an evidence review into vitamin D and COVID-19, the NICE report that followed concluded that there was no evidence to support taking vitamin D supplements to prevent or treat COVID-19. This caused uproar amongst nutrition and industry experts with criticism focused around the fact that it included only 5 papers ignoring a vast amount of pre-preprint studies, excluded on the basis they were yet to be peer-reviewed. It also ignored thousands of studies published on prior coronoviruses and vitamin D.

Dr Davies' response to concerns regarding overdosing is:

"People make this hormone when their skin is exposed to the sun. If there is a danger of people overdosing on this hormone then where are those people and why aren't we overdosing when we spend too much time in the sun? Coronovirus has killed one million people and governments are concerned about vitamin D overdosing!"

The NHS website it states that during autumn and winter (from October until the end of March) the sun isn't strong enough in the UK to produce vitamin D. That means we have to rely on getting it just from the food we eat; this includes oily fish, red meat, liver and egg yolks. If you're not regularly including these foods in your diet then you are at risk of not getting enough vitamin D. Taking a supplement therefore helps to keep levels of the vitamin topped up during winter months. The NHS also advises that people do not take more than 4000 IU daily as it could be harmful.

Current UK recommendations for vitamin D intake are conservative

Martin Hewison, Professor of Molecular Endocrinology at the University of Birmingham and an expert on the subject of vitamin D who is not part of the alliance, agreed the current UK recommendations for vitamin D intake are very conservative:

"400 IU/day is not meant to optimise vitamin D but it is simply a level that SACN estimated that most UK people can reach to avoid severe vitamin D deficiency."

"However, we do not know what the optimal level of vitamin D is for good immune function because these studies have simply not been carried out."

Despite this statement, Professor Hewison acknowledges the position of those recommending 4000 IU daily and puts forward two important questions that are still to be answered: Is vitamin D protecting against actual COVID-19 infection in the general population? Does vitamin D improve prognosis once you are infected? He says:

"The answer may be both but I am guessing that the requirements for vitamin D are difference for these two facets of COVID-19, Possibly you need higher levels to protect once you are infected."

It would seem uncontroversial to conclude that we should be more rigorously promoting efforts to achieve reference nutrient intakes of vitamin D. The benefits of vitamin D for bone and muscle health are well known and backed by science, but there is a chance that it might also reduce the impact of COVID-19 in populations where vitamin D deficiency is prevalent. One could say there is nothing to lose and potentially much to gain from a vitamin D intervention.

A healthy balanced diet is the best way to consume all the nutrients we need. Sometimes however this isn't possible and then supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying any supplements or herbal medicines.