Does vitamin D protect against COVID-19?
I hope you are safe and well. You may have read claims in the media suggesting a vitamin D deficiency is linked to poorer outcomes from COVID-19, and in turn, that we should consider taking vitamin D supplements to protect ourselves. Is this all just hype, or could vitamin D really help in the fight against COVID-19?
As winter emerges in the Northern Hemisphere and cases surge to new highs in Europe and the USA, we asked 5 experts to share the facts..
Does vitamin D protect against COVID-19?
80% Uncertain via 5 experts
Otherwise known as the “Sunshine” vitamin, adequate amounts of Vitamin D is important for general health. Dr. Anthony Fauci, the US governments top immunologist recently said:
If you are deficient in Vitamin-D, that does have an impact on your susceptibility to infection
So how does Vitamin D potentially help our immunity? Professor Elina Hyppönen, nutritional epidemiologist from the University of South Australia tells us how.
Vitamin D, the immune system and respiratory infections
At least in theory, there may be something to the claims that Vitamin D helps protect against COVID. Nearly all immune cells have vitamin D receptors, showing vitamin D interacts with the immune system. The active vitamin D hormone, calcitriol, helps regulate both the innate and adaptive immune systems, our first and second lines of defence against pathogens.
And vitamin D deficiency is associated with immune dysregulation, a breakdown or change in the control of immune system processes. Many of the ways calcitriol affects the immune system are directly relevant to our ability to defend against viruses. For example, calcitriol triggers the production of cathelicidin and other defensins – natural antivirals capable of preventing the virus from replicating and entering a cell.
Calcitriol can also increase the number of a particular type of immune cell (CD8+ T cells), which play a critical role in clearing acute viral infections (such as influenza) in the lungs. Calcitriol also suppresses pro-inflammatory cytokines, molecules secreted from immune cells which, as their name suggests, promote inflammation. Some scientists have suggested vitamin D might help to alleviate the “cytokine storm” described in the most severe COVID-19 cases.
What about Vitamin D and COVID-19?
Uncertain say the experts.
There is currently no evidence that vitamin D protects against COVID-19, either in terms of initial infection or severity of disease once infected
writes Dr Claire Hastie from the University of Glasgow.
Most studies have linked vitamin D levels to COVID infections on population data - and there are some interesting links being made writes Dr Karin Amrein, a Vitamin D expert from Austria. The first appearance of COVID came from winter months in the Northern Hemisphere, while "the higher incidence in non-white populations and worse outcomes would suggest a role of vitamin D."
There are very good data that vitamin D reduces acute respiratory infections and asthma exacerbations. Recent US data from a large dataset clearly showed a higher rate of COVID-19 positivity in vitamin D deficient individuals.
writes Dr Amrein.
However Dr Claire Hastie from the University of Glasgow disagrees any link can be drawn about Vitamin D writing
Studies that suggest a link have either failed to take confounding variables into account... or they measured 25(OH)D once patients are already ill. This introduces the possibility of reverse causation, i.e. COVID-19 leading to lower vitamin D rather than low vitamin D leading to COVID-19, because vitamin D is a negative acute phase reactant. All existing evidence is limited due to its observational nature. For a definitive answer on whether there is a link we await the results of randomised controlled trials (RCTs), of which there are several underway.
Vitamin D Low Risk Strategy?
Given the potential immune benefit, some experts see supplementation as a low risk strategy, particularly during the winter. Dr. Anthony Fauci, recently said he takes Vitamin-D supplements:
If you are deficient in Vitamin-D, that does have an impact on your susceptibility to infection….So I would not mind recommending—and I do it myself—taking vitamin-D supplements.
Although there is no evidence so far that Vitamin D protects against COVID-19, other experts like Professor Reinhold Vieth from the University of Toronto agree with Dr Fauci, writing that taking Vitamin D supplements is a “no lose proposition”. However he does say that unfortunately certainty on the issue will only come in a year or two - “too late to make any difference to people”.
And for those north of 35degrees latitude, you wont likely get enough Vitamin-D naturally during winter writes Professor Vieth:
Human bodies possess a factory that makes vitamin D; it is called the skin. Winter clothing shuts down 95% of that factory (face and hands is only 5% of skin surface). Beyond that, a rule of thumb is that you need the sun to be at least 45 degrees above the horizon (a UV index of at least 3) for it to provide the skin of a white person enough ultraviolet light to make a useful amount of vitamin D….
Fortunately, vitamin D disappears slowly out of the body, so our summer gain in vitamin D helps to prevent severe deficiency during winter. The prudent thing is to keep supplementing with vitamin D all year.
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