A look into the link between Vitamin D and Covid-19 mortality

The ongoing pandemic has seen great strides taken to better understand the nature of Covid-19. Though this has been the case from when the severity of virus became clear, it now forms an increasingly clear part of government policy. Whereas initial responses focused on the need to halt and contain, greater familiarity has informed International efforts to find steady solutions outside of self-imposed lockdowns.

Plans to coordinate a response began with attempts to consider the conditions under which the virus thrives. This included other factors which may play a role in its acceleration, prevention, and its skewed effect on certain communities in comparison to others (given yesterday’s reluctant development, this has become all the more clearer). The significance of socioeconomic factors has rightly been covered, but new research suggesting that vitamin D may be of consequence when considering lower mortality rates associated with the virus has begun to gain traction.

Anglia Ruskin Study

This is laid out in a new Anglia Ruskin study which suggests that there may be some association between Vitamin D and low Covid death rates.

The study from the Cambridge based university was led by Dr Lee Smith and was collaborated on with Mr Petre Cristian Llie, a lead urologist at Queen Elizabeth Hospital King' s Lynn. It included cases across 20 European countries and has since been published in the journal Aging Clinical and Experimental Research.

The paper notes that previous studies had observed an association between low levels of vitamin D and 'susceptibility to acute respiratory tract infections.' As is stated on the Anglian Ruskin website, this is because Vitamin D modulates the response of white blood cells. In doing this, it prevents the white blood cells from releasing too many inflammatory cytokines. The Covid-19 virus is known to cause an excess of pro-inflammatory cytokines which can among other things, damage the organs and lead to death.

In reporting on the study, Anglia Ruskin use both Italy and Spain as examples of where this effect can be seen. It discusses the disparity in vitamin D levels between people in Southern and Northern Europe and has highlighted how this may be a factor when viewing the harsh effect of the virus in southern countries such as Spain and Italy. By comparison, they consider how Scandinavian nations in the north of Europe are among the countries with the lowest numbers of Covid-19 cases and mortality rates. These are countries where there is "possibly less sun avoidance" and "greater consumption of cod liver oil and vitamin D supplements." They note that a contributing factor to comparatively lower Vitamin D levels elsewhere may be because "people in southern Europe avoid strong sun, while skin pigmentation also reduces natural vitamin D synthesis." But as the authors admit themselves when comparing the cases of Italy and Spain to northern Europe, this correlation does not prove any definitive causation between vitamin D and the severity of covid-19 cases. Nor too should it be mistaken for some sort of answer to covid prevention.

Significance for Afro-Caribbean and South Asian backgrounds

The latter explanation regarding pigmentation is of particular importance to people from Afro-Caribbean and South Asian backgrounds. Vitamin D is made in the skin by the action of sunlight and this is the main source of vitamin D for most people. Nicola M. Lowe and Issak Bhojani’s 2017 paper provides a more comprehensive breakdown describing it as occurring "through the synthesis of this prehormone (vitamin D) in the skin during exposure to ultraviolet B (UVB) radiation."

They once more add to this, stating:

“Achieving optimal vitamin D status is therefore largely dependent upon adequate exposure of the skin to sunlight, however, the length of exposure required varies with latitude and season, and is also dependent upon skin pigmentation, with darker skin requiring greater exposure than fair skin due to the protective effects of melanin against UVB radiation.”

This means that people from African, South Asian and Caribbean backgrounds need to consider supplementing their vitamin D intake all year round, as we may not be able produce enough in the English sun.

An understanding of this link could prove significant. Better knowledge of the factors which may influence the virus will inevitably lead to more effective policy measures. Even more importantly, it will leave the public better informed and more willing to follow the necessary precautions as they are advised.

How the theory holds up with the science

Professor Susan Lanham-New, offered further insight into the topic. When discussing the role of Vitamin D on the Guardian's science weekly she emphasised how the rationale behind suggestions that vitamin D deficiency was correlated with more severe Covid-19 infections was impacted by two important factors: the vitamin D receptor and vitamin D metabolic enzymes in immune cells.

This forms part of the basis in the association between low vitamin D and the increase in upper respiratory tract infections which translate to more severe spells of Covid-19. The professor however applied caution when coming down on any definitive conclusion. Instead, she stressed that whilst these indicate that 'the mechanisms' for this theory are there, the science is still yet to fully catch up.

She states:

“The British medical journal paper that I’ve led on with 21 co-authors was to try and pull together all the current scientific evidence as we have it, and we’re now working on a second paper because things are moving so quickly. As it currently stands we see no difference in vitamin D status between covid-19 cases and negative controls. However, there are other studies such as a very important study from Indonesia which showed much lower vitamin D status in those who had severity of covid-19. What we don’t yet have, is any vitamin D randomized control trails so I think the message that we need to get out is that we must avoid a deficiency in our population but those calls for high doses of vitamin D are on the basis of mechanisms rather than strong scientific data.”

The call for more rigorous scientific study so as to guard against excessive vitamin D intake has been mirrored elsewhere. Nikki Hancocks of Nutraingridients covered the fears shared by many scientists that reports indicating that high doses of vitamin D could treat the virus are not only based on speculation but may be harmful to public health. These worries include any views that vitamin D could somehow represent a ‘magic bullet’ in the fight against the virus.

Common sense approach

Despite the research suggesting it could play a factor, any definitive conclusion is still some way away. Given this, Professor Susan Lanham-New’s emphasis on avoiding vitamin D deficiency as opposed to storming the shelves for all things vitamin D may strike the right balance. Aside from this, the already existing advice from PHE should also be consulted. The updated advice recommends that people should take 10 micrograms of vitamin D a day to keep your bones and muscles healthy. This is because people may not be getting enough vitamin D from sunlight as many are indoors for most of the day due to lockdown measures.

What are the recommended sources?

Even though it may be hard for us to get our full daily vitamin D intake from food alone, a well balanced diet is still greatly beneficial in ensuring we are closer to being vitamin D sufficient. These include oily fish – such as salmon, sardines, herring and mackerel, red meat, liver, egg yolks, fortified foods – such as most fat spreads and some breakfast cereals.

Mayowa Ayodele

For further updates regarding recommended vitamin D intake and sources, click here and visit the NHS website.