If there is one thing you can rely on in this pandemic, it is: at least once a month a new article will appear in the media claiming that vitamin D helps prevent Covid-19.
The case is simple: we know that vitamin D – “sun vitamin” – is involved in immune function, so could it help us fight the virus?
Some, like Labor MP Rupa Huq, are pretty sure of the answer. She wrote on Tuesday (January 12th) an article in Evening Standard where he described vitamin D as a “miracle” that “gives us all hope to eliminate this dreaded disease.” She wrote that its benefits are “hidden” – she probably suggested, because cheap vitamin pills cannot be monetized by Big Pharma and are less glamorous than a vaccine.
Huq’s article appeared a few days after the publication of a Observer the song describing how she and David Davis, the Conservative MP, had become unlikely allies on the issue, campaigning to reduce what they consider to be vitamin D deficiency in the UK. Huq and Davis are frustrated that bodies such as Public Health England say there is not enough evidence to promote the vitamin, which Davis says could “save tens of thousands of lives” during the pandemic.
Why do do experts disagree with Huq and Davis? What does the evidence say about vitamin D and Covid-19? You might think that after almost a year of studying, we would have a pretty good idea about the answer. Away from.
Most research on Covid-19 / vitamin D is in the form of observational studies – in which researchers look at the correlation of blood vitamin D levels with the risk of taking Covid-19 or the severity of the disease. So far, there have been quite a few such studies, and researchers have done meta-analyzes to share all the data and try to draw broad conclusions.
If you simply go through these meta-analyzes, the case may seem optimistic. one The meta-analysis found that although vitamin D was not associated with the risk of taking Covid-19, severe cases were more likely to involve a deficiency. Another found that depending on how you measure it, a higher level of vitamin D is sometimes associated with a lower risk of infection and hospitalization. One-third found lower levels of vitamin D in patients with Covid-19 compared to those without the disease.
[See also: Stuart Ritchie on the “three Cs” key to preventing the spread of coronavirus]
Exciting, isn’t it? Not realy. Much of the research is of low quality, with small samples and questionable analyzes. More importantly, observational research is affected by what epidemiologists call “confusing.” For example, if older people or those with darker skin have a higher risk of vitamin D deficiency and are more at risk for severe Covid-19 for other reasons, this type of study could be incorrectly linked to of disease – even if one does not cause the other.
We need randomized trials, in which researchers give patients with Covid-19 either vitamin D or a placebo and test whether the vitamin causes a better result. Surprisingly, there are only two so far. The first was a Spanish study that found that patients with Covid-19 who were given a type of vitamin D supplement tended to do better. The ones mentioned above Observer The article said that this study “came to almost unequivocally demonstrate that low levels of vitamin D play a key role in increasing the death rate.” This is dramatically far from reality: this was a pilot study with only 76 participants, and some clear FAULTS in its design.
The second is a little bigger study from Brazil, which did not find quite convincing benefits of vitamin D supplementation for patients with severe Covid. It is not yet published in a peer-reviewed journal, but strangely it is not mentioned by vitamin D advocates.
You may be thinking: what is the disadvantage? Vitamin D is cheap. We all stay indoors during the lockout and therefore receive less sunlight. Even though vitamin D doesn’t help fight Covid-19, is it definitely a good idea to take supplements anyway? But this is a the motte-and-bailey argument – if someone makes a very specific, controversial statement, that statement is attacked and withdrawn into a much more general position – but more defensible. I wasn’t talking about general benefits of vitamin D – we were talking about benefits for Covid-19. And the honest answer at this point is that science has failed to give us any clarity: we simply do not know if it has an effect.
And there you disadvantages. There is a new, more transmissible version of the Covid-19, and we need people to be very careful not to catch it. Promoting the idea that there is a simple, dramatically effective solution – “wonderstuff”! – which stimulates our immune system and prevents disease could easily bring people into a false sense of security: “I took my vitamin D capsule, so maybe I can do without wearing a mask today.”
Many more studies with vitamin D and Covid-19 are on the way, so we’ll get a more definitive answer soon. Until then, let’s get rid of the exaggerated claims about almost magical substances and sinister conspiracies. He may feel dissatisfied, but, as in so many parts of the coronavirus debate, the only scientifically sensitive view of vitamin D is one of uncertainty.
[See also: Stuart Ritchie on Covid-19 and the problem of anti-vaxxers]