Vitamin D and COVID-19: What Do We Know?

In Sigma Statements by Niamh Aspell8 Comments

What's the Deal with Vitamin D & COVID?

  • Vitamin D deficiency has been proposed to play a role in risk of SARS-CoV-2 infection and/or risk or worse outcomes from COVID-19.
  • Vitamin D supplementation has also been explored as a potential adjunct treatment for those with severe COVID-19 infection.
  • Previously, vitamin D supplementation has been suggested to have some benefit against acute respiratory infections generally.

But what can we conclude based on current evidence?

This Sigma Statement will attempt to summarize the available evidence regarding how the risk of COVID-19 infection and mortality is potentially impacted by:

  1. Vitamin D status
  2. Vitamin D genotypes
  3. Vitamin D supplementation

In this Sigma Statment:

  1. Introduction: COVID and preventative measures
  2. Comparision to other coronaviruses
  3. Clinical vulnerability and COVID-19
  4. Vitamin D physiology
  5. Vitamin D status and risk factors for vitamin D deficiency
  6. Mechanistic evidence for vitamin D and COVID-19
  7. Observational studies of vitamin D status and COVID-19
  8. Mendelian Randomisation studies
  9. Vitamin D supplement use and COVID-19
  10. Concluding thoughts: Pragmatic Steps
  11. Summary of Key Points

Introduction: COVID & Preventative Measures

Coronavirus disease (COVID-19) is a respiratory and systemic disorder caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) or novel Coronavirus (nCoV). Much is still unknown about SARS viruses, but SARS-CoV-2 spreads faster and farther than the 2003 SARS-CoV-1 virus. This is likely because of how easily it is transmitted from person to person, even from asymptomatic carriers of the virus.

At present (January 2022), there is no scientifically approved curative treatment for the virus; as a result, prevention remains to be the best strategy to combat infection. To this point a set of preventative measures recommended by the WHO to prevent infection and slow transmission endorsed worldwide by most governments and public health agencies, with varying levels of compliance by the general population. Such measures include:

  • vaccination
  • physical distancing
  • mask wearing
  • practicing good hygiene
  • if unwell, to self-isolate until recovered

Beyond this, additional preventative and therapeutic measures have been explored, to reduce the risk of infection but also to reduce the severity of symptoms in those who do contract the virus. Vitamin D deficiency has been proposed to play a role in coronavirus infection (e.g. here and here). In addition, vitamin D supplementation has been explored as a potential adjunct treatment for those with severe COVID-19 infection, i.e., requiring hospitalisation, intensive care unit (ICU) admission and/or those requiring oxygen support.

In the decade preceding the coronavirus pandemic, a meta-analysis of randomised controlled trials (RCTs) reported protective effects of vitamin D supplementation against acute respiratory infections (ARIs). However, the effects are modest and there is a lack of homogeneity (the similarity of the results of studies included) across studies.

This Sigma Statement aims to summarize the available evidence regarding how the risk of COVID-19 infection and mortality is potentially impacted by vitamin D status, vitamin D genotypes, and vitamin D supplementation.

Comparison to Other Coronaviruses

Coronaviruses are a family of enveloped RNA viruses broadly distributed in humans and animals that cause acute and chronic diseases. SARS-CoV-2 is the seventh human coronavirus to be identified. Of the six coronavirus species previously known to cause human diseases, four typically cause common cold symptoms. However, the other two , namely SARS- and MERS- (Middle East respiratory syndrome) coronavirus, can cause fatal respiratory disease.

With this latest coronavirus, SARS-CoV-2, infection can remain asymptomatic or cause modest symptoms. Severely sick patients require hospital admission and about 20 % of hospitalized patients will develop Acute Respiratory Distress Syndrome (ARDS) and require intensive care unit (ICU) treatment. A certain percentage of cases will also be fatal, with estimates of both the case fatality rate and crude mortality rate varying by location, time, and other factors. Currently case fatality rate estimates vary by country from 0.35 - 2.75%, with a world wide average of 1.8%. However, as put by Our World in Data, it is important to note that the case fatality rate "is the ratio between the number of confirmed deaths from the disease and the number of confirmed cases, not total cases. That means that it is not the same as – and, in fast-moving situations like COVID-19, probably not even very close to – the true risk for an infected person."

Clinical Vulnerability and COVID-19

Since the beginning of the pandemic in early 2020, governments worldwide have responded with public health measures to protect the most vulnerable in society. Initially this focused on clinical vulnerabilities, as early data indicated that older adults, particularly those with poor health status or with dependencies and requiring institutional care, to be most vulnerable to COVID-19 death. As the pandemic continued into the first wave (February to August 2020), more data was generated to describe the profile of those most likely to experience severe COVID-19 infection, requiring hospitalisation, and potentially ICU care, and ultimately increasing risk of mortality. Those defined as ‘clinically extremely vulnerable’ to the virus included:

  • people with respiratory conditions (severe asthma, COPD, bronchiectasis, and cystic fibrosis)
  • compromised immune systems (such as those receiving treatment for cancer)
  • older adults
  • those with Class 3 obesity (defined as a body mass index of >40 kg/m2)

In addition to clinical vulnerability, it is now well established that those with lower socio-economic status are also at increased risk of COVID-19 infection and poorer outcomes. The risk factors for both severe coronavirus infection and vitamin D deficiency have many similarities, which has led researchers to investigate a potential relationship.

Vitamin D Physiology

Vitamin D is a precursor of the active form 1,25(OH)2D (calcitriol) and is present in two forms:

  1. Vitamin D3 (cholecalciferol)
  2. Vitamin D2 (ergocalciferol)

The main source in humans is via action of solar ultraviolet-B (UVB) radiation (270nm-300nm) on skin, converting 7-dehydrocholesterol (provitamin D3) into pre-vitamin D3, which is then rapidly converted to vitamin D3 as illustrated in the image below.

Image from: Keane et al., 2018, Nutrients 10(4):496

Vitamin D2 is produced via UVB radiation on plant sources such as mushrooms and yeast. Natural dietary sources of vitamin D3 are few, and include fish liver oils, oily fish, egg yolks and some fortified foods (e.g., some dairy and breakfast cereals) and supplements.

Irrespective of how it is acquired, vitamin D offers limited function until it has been activated, a process which requires two hydroxylation steps, as illustrated in the image above, namely:

  1. First, in the liver several enzymes but primarily vitamin D3 25-hydroxylase (CYP2RA), which converts it to the inactive precursor, 25-hydroxy vitamin D [25(OH)D]. This 25(OH)D is the prominent circulating form in humans and so it is the form that is measured to determine vitamin D status.

  2. The second hydroxylation step occurs in the tubular cells of the kidney, where the inactive 25(OH)D is converted to the biologically active metabolite 1, 25-dihydroxy vitamin D3 [1,25(OH)2D3], via the action of the enzyme 25vitamin D3-1α- hydroxylase (CYP27B1).

The active form of vitamin D, 1,25(OH)2D3, plays many important roles around the body, including modulating calcium and phosphate homeostasis. It is also present in many tissues including the kidneys, brain, immune cells, cardiovascular systems and pancreatic islets. Due to its ability to be synthesised endogenously, vitamin D is widely accepted to be a steroid hormone, as opposed to a vitamin by its classic definition.

Vitamin D Status and Risk Factors for Vitamin D Deficiency

Serum 25(OH)D is accepted as the most accurate measure of vitamin D status, however, there is less agreement on how to define 'deficiency' in the general population. Indeed, different groups provide different cut off points:

  • The Institute of Medicine (IOM) advocate serum 25(OH)D concentrations ≥50nmol/L for bone health and consider levels <30 nmol/L to be deficient. The term ‘vitamin D insufficiency’ is used to describe serum levels of ≥30-50 nmol/L.
  • In contrast, the Endocrine Society recommends serum 25(OH)D levels ≥ 75nmol/L to maximise an effect on bone and muscle metabolism. They deem vitamin D deficiency to be a 25(OH)D below 50 nmol/L (20 ng/ml), and vitamin D insufficiency as a 25(OH)D of  50–74 nmol/L (21–29 ng/ml).

Suboptimal levels of vitamin D are much more common than clinical toxicity, which is rare.

Several factors influence vitamin D status including:

  • skin pigmentation
  • use of sunscreen or concealing clothing
  • season
  • latitude
  • being older or institutionalised
  • obesity
  • malabsorption
  • renal and liver disease
  • medication use

In general, UVB radiation on skin is the main source of vitamin D for humans. In countries north of the equator (40-60°N), vitamin D UVB doses are inadequate for 6 months of the year (October- March). The efficiency of UVB vitamin D production is reduced by as much as 50% in older adults compared to younger adults. This is due skin thinness, decreased skin integrity, and a reduction in transdermal cholesterol, that occures with advancing age. Additionally, there are also behavioural and social changes seen with advancing age that further limit vitamin D production, namely:

  • Less time spent outdoors due to ill health or limited mobility (institutionalised or homebound)
  • medication use (loop diuretics, statins, glucocorticoids)
  • changes in body composition (increase in fat and decrease in muscle)
  • sun avoidance (melanoma risk)
  • reduced skin exposure (clothing and colder temperatures)

The striking overlap between risk factors for severe COVID-19 and vitamin D deficiency (i.e. older age, institulisatised adults, and those of black or Asian ethnic origin) has resulted in many researchers to hypothesise that vitamin D supplementation could provide opportunity as a preventative or therapeutic option for COVID-19.

Mechanistic Evidence for Vitamin D and COVID-19

From a mechanistic angle there is logic in exploring the potential for vitamin D metabolites to support innate antiviral effector mechanisms, in both:

  1. the early viraemic stages in SARS-COV-2
  2. later increased inflammatory phases of COVID-19

Vitamin D metabolites have long been known to support innate antiviral mechanisms (see here and here), including induction of antimicrobial peptides and autophagy. Of particular interest, vitamin D has important antiviral properties, including the induction of cathelicidin and b2-defensins synthesis, both of which have significant antibiotic and antiviral effects.

Chen and colleagues compared the clinical and immunological characteristics between moderate and severe COVID-19. They found that respiratory distress on admission is associated with unfavourable outcomes. Severe COVID-19 is associated with:

  • increased cytokine levels (IL-6, IL-10, and TNF-α)
  • lymphopenia (in CD4+ and CD8+ T cells)
  • decreased IFN-γ expression in CD4+ T cells

Overall, this study characterized the ‘cytokine storm’ in severe COVID-19 and provided insights into immunotherapeutics and vaccine design. Recently, Adrian Martineau showed that airway diseases are associated with dysregulated vitamin D metabolism, raising the possibility that vitamin D deficiency may occur as a result of pulmonary inflammation.

Observational Studies of Vitamin D Status and COVID-19

Circulating levels of 25(OH)D and incidence and severity of COVID-19 have been explored by numerous investigators. Increased vitamin D levels have been proposed to protect against COVID-19 based on in vitro, observational, and ecological studies. Two ecological studies have reported inverse correlations between national estimates of vitamin D status and COVID-19 incidence and mortality in Europe. Mariani et al., utilised publicly available estimates of national prevalence of vitamin D deficiency (<50 mmol/l) across 46 countries and reported an association with risk of being infected with COVID-19, severity of the disease, and risk of death.

Another study in a single centre in the US, included 489 COVID-19 patients who had a measurement of 25(OH)D within 1 year of receiving a COVID-19 positive test. Vitamin D status was estimated based on ‘most likely deficient’ since previous analysis and COVID-19 testing. The study was one of a few that controlled for important confounders, such as sex, BMI, medical history, and race. "Likely deficient" vitamin D status was associated with increased COVID-19 risk (OR 1.77), in those who had not commenced vitamin D treatment since their previous diagnosis of deficiency (as reported on the hospital electronic system).

A study in Israel reported independent associations between low 25(OH)D levels (measured prior to the COVID-19 pandemic) and subsequent incidence and severity of COVID-19. This investigation is limited by the use of historic 25(OH)D measurements, which might not reflect circulating concentrations at the time of exposure to SARS-COV-2. On the other hand, a study in a northern Italy hospital found no association between vitamin D and COVID-19.

In a review article, researchers in Italy concluded that poor vitamin D status appears to be linked to an increased risk of SARS-CoV-2 infection, but age, sex, and comorbidities seem to play a more important role in COVID-19 severity and mortality. A different group of Italian researchers published an observational study of 324 patients with COVID-19 that found taking vitamin D supplements was not linked to risk of hospitalization but vitamin D deficiency was associated with a higher risk of dying if hospitalized.

Current evidence is encouraging but conflicting. As described above, vitamin D levels are associated with numerous confounding variables, and the associations may not be causal. Therefore to minimize bias due to confounding when considering this relationship, Mendelian Randomization (MR) studies may offer an important insight.

Mendelian Randomisation Studies: Vitamin D and COVID

Guillaume Butler-Laporte and collegues utilised a genome-wide association study (GWAS) of 443,734 participants of European ancestry (including 401,460 from the UK Biobank). The researchers did not observe evidence to support an association between 25(OH)D levels and COVID-19 susceptibility, severity, or hospitalization. Hence, vitamin D supplementation as a means of protecting against worsened COVID-19 outcomes was not supported by genetic evidence.

Similar was reported by Cui et al., who demonstrated that genetically lower serum 25(OH)D concentrations were not causally associated with COVID-19 susceptibility, severity or hospitalized traits.

In another study researchers conducted a regression analysis (a statistical method that basically shows the relationship between variables and the outcome of interest) to identify associations between vitamin D factors and COVID-19 (risk of infection, hospitalisation and death) in 417,342 participants from UK Biobank. Additionally, the authors performed a MR study to look for evidence of a causal effect. The main MR analysis did not show that genetically-predicted vitamin D levels are causally associated with COVID-19 risk (OR = 0.77, 95% CI 0.55–1.11, P = 0.160). Interestingly, the authors found no strong association between vitamin D levels and COVID-19 risk or severity after adjustment for confounders, results that are in accordance with other recently published evidence.

It is important to note that the vitamin D UK biobank samples were collected over a decade ago, and technique used (the DiaSorin immunoassay) is deemed inferior to other techniques, such as Liquid Chromatography with tandem Mass Spectrometry (LC-MS/MS). Furthermore, as the authors acknowledged, not all participants were tested for present (or past) COVID-19 infection; and so as it's possible that some of the participants who were in the control group could have actually been previously asymptomatic infected individuals, this introduces a source of bias.

Vitamin D Supplement Use and COVID-19

In a study investigating frail older in-patients with COVID-19, regular vitamin D supplement use in the year prior to a COVID-19 diagnosis was associated with less severe disease and better survival than taking no vitamin D or receiving supplementation shortly after diagnosis. Below is a figure from that study, showing Kaplan–Meier estimates of the cumulative probability of COVID-19 participants’ survival according to vitamin D interventions.

  • Arm 1: regular vitamin D supplementation
  • Arm 2: vitamin D supplementation initiated after COVID-19 diagnosis
  • Arm 3: no vitamin D supplementation

From: Annweiler et al., Nutrients 2020, 12(11), 3377

Another study investigated the potential benefits of delivering a single high dose of vitamin D3 (200, 000 IU) in patients with moderate to severe COVID-19. The investigators determined that bolus doses of vitamin D did not significantly reduce hospital length of stay, as shown in the figure below.

From: Murai et al., JAMA. 2021;325(11):1053-1060
Copyright © 2021, American Medical Association

To date, RCTs administering bolus doses of vitamin D and various outcomes, continually fail to demonstrate beneficial effects. A pilot RCT of 76 in-patients with COVID-19 in Spain found that treatment with high-dose vitamin D (in combination with standard care of hydroxychloroquine and azithromycin), significantly reduced the risk of ICU admission. This was a parallel pilot randomized open label, double-masked clinical study aiming to assess whether vitamin D3  can reduce the need for admission to ICU, and related death. Serum 25(OH)D concentrations at baseline or during treatment are not available, and how baseline vitamin D status modifies these results is unknown. The ongoing multicenter (15 sites) RCT using vitamin D3 will be carried out with the number of patients recalculated from the data provided by the original pilot findings.

Treatment trials may be challenging to detect a signal for vitamin D supplementation in severe COVID-19 for two reasons:

  1. Patients tend to present to hospital in the hyperinflammatory stage of disease, so it might be too late to gain benefit from antiviral effects induced by vitamin D supplementation.
  2. It is hard to show effects of micronutrients above pharmacology agents, such as dexamethasone, which has potent anti-inflammatory actions and now represents the same standard of care in severe disease.

As shown in many vitamin D supplementation trials, for various outcomes, response and improved outcomes is most observed in those with low baseline 25(OH)D concentrations.

Precarious advice about very high and potentially harmful vitamin D supplementation, which lacks an evidence base, has been circulating during the pandemic and scientific communications should take effort to address such misinformation. This is described in more detail in this piece by Prof. Susan Lanham-New and collegues.

Concluding Thoughts: Pragmatic Steps

Whilst the evidence for vitamin D supplementation in the prevention of SARS-COV-2 infection or severity of outcomes in patients is lacking, many efforts have been made to better understand how vitamin D strategies could be utilised to offset some of the clinical consequences. Irrespective of the strength of evidence, or the COVID-19 pandemic, vitamin D deficiency continues to be a public health issue, particularly of older adults, institutionalised elderly, persons with obesity, and black and Asian ethnic groups. The low costs of vitamin D and its general safety, support arguments for population-level supplementation, perhaps for targeting groups at high risk for vitamin D deficiency and/or COVID-19.

In October 2020, 2.7 million people in England (those on the COVID-19 clinically extremely vulnerable list) were offered free daily vitamin D supplements containing 10 microgram (400IU) for the winter months by the UK government. This vulnerable group are encouraged to ‘opt-in’ as they are likely to have been indoors more than usual, as recommended by protective COVID-19 health measures, so might not have been able to obtain enough vitamin D from sunlight. The existing government advice in the UK, and many European countries is for everyone to take a vitamin D supplement during the winter months. Many population-based studies continue to report low vitamin D supplement use. Vitamin D fortification policies are still under (long and extended) debate.

Summary of Key Points

  1. The active form of vitamin D, 1,25(OH)2D3, plays many important roles around the body.

  2. There is an overlap between risk factors for severe COVID-19 and vitamin D deficiency.

  3. There are plausible mechanisms on which to suspect vitamin D metabolites could exert antiviral effects in the early stages of being exposed to SARS-COV-2, and/or during later phases of actual COVID-19 disease state.

  4. In relation to observational studies, there is encouraging data but overall the evidence is still conflicting.

  5. Mendelian randomization studies have thus far shown that genetically lower vitamin D status is not causally associated with COVID-19 susceptibility, severity or hospitalization.

  6. Trials of vitamin D supplementation have shown mixed results. But such treatment trials may be challenging to detect a signal for vitamin D supplementation in severe COVID-19 for a number of reasons. In general, as is the case for other health outcomes, it is likely that response and improved outcomes will be most observed in those with low baseline 25(OH)D levels.

  7. Vitamin D deficiency continues to be a public health issue, particularly of older adults, institutionalised elderly, persons with obesity, and black and Asian ethnic groups.

  8. Currently, the evidence for vitamin D supplementation as an intervention doesn't have clear and robust evidence to support it. However, despite the evidence strength, given the low costs of vitamin D and its general safety, good arguments could be made for population-level supplementation, particularly targeting groups at high risk for vitamin D deficiency and/or COVID-19.

About this Statement


  1. Hi Dr Aspell, I just read the statement and I have a few corrections/questions/comments.

    1. Asymptomatic carriers definition. You state that “An asymptomatic carrier is an individual who has not completed a laboratory test but unknowingly has coronavirus but shows no symptoms during the complete course of infection”. That it’s not the definition of an asymptomatic carrier. The testing of that person or their knowledge of their infection is irrelevant to their status as an asymptomatic carrier. You can know you have covid, confirmed by the lab, show no symptoms and you will still be an asymptomatic carrier.

    2. In the Comparison to Other Coronaviruses part, it says “about 20 % of hospitalized patients will develop Acute Respiratory Distress Syndrome (ARDS)”. But the study linked says “Calculation of weighted averages (…) indicate that among hospitalized COVID-19 patients, approximately 1/3 (33%) develop ARDS”. In addition, that study was published early 2020, before Delta. The incidence of ARDS is hard to establish and depending on the study it ranges from 3% to 60%.

    What I find a bit off especially considering the caliber of the statements Sigma Nutrition puts out is some of the studies presented here especially when linked without context or critical analysis, especially two of them:

    3. In the Observational Studies of Vitamin D Status and COVID-19 part the “Borsche et al” meta-analysis is linked in the sentence “Increased vitamin D levels have been proposed to protect against COVID-19 based on in vitro, observational, and ecological studies.” This paper is in my honest opinion absolute garbage. It’s a “systematic review/meta-analysis”, that doesn’t even mention how they excluded or included articles made by three “independent researchers” that have never published a paper before and none of them are biologists/doctors/epidemiologists or anything remotely connected to biomedical research. They conclude I kid you not that a vitamin D concentration of 50ng/ml means there is a theoretical point of zero mortality (????). A paper like this should never be linked without proper context (or even linked at all).

    4. In the Vitamin D Supplement Use and COVID-19 part the Spanish Castillo et al paper is mentioned. It is described by the authors as an open-label double-masked trial, which to me makes no sense and the methods don’t really explain how it can be both open-label and double-blind. The methods imply that the doctors – who were the ones in charge of sending a patient to ICU – knew who was getting the treatment and who wasn’t. That’s not a blinded study. In addition, the decision to send a patient to the ICU was decided by a “selection committee” in part due to the presence of co-morbidities (supposedly explained better in the Supplementary Material, but there is no Supplementary Material distributed with the paper either). There was a significant imbalance in some of the comorbidities (high blood pressure and diabetes, both extremely linked to covid outcomes), which renders the study results quite meaningless.

    I do not entirely disagree with the conclusions, I just think some of the studies presented are extremely biased and very poorly done, without those facts being presented in this statement.

    1. And my apologies if this sounded rude, I did in no way mean it like that. As someone that works at a hospital and sees the harm covid misinformation does day in and day out I just have a very low tolerance to it. Some of the studies linked here have been used by quacks to push non valid treatments or even say that vitamin D cures covid. The main leader of the Córdoba study linked went on the news saying his Vitamin D treatment has saved thousands of lives. So you can understand my absolute hate for that study.

    2. Thank you, Anna, for your detailed review and feedback. You have raised many important points and I have provided some clarifications.

      1. Of course, the text has been updated to reflect that testing is irrelevant.

      2. Yes, I agree, the incidence rates for ARDS vary and will depend on many factors including age, co-morbidities, male sex, socio-economic status other clinical parameters, to name a few. Additionally, considering the time period of retrospective analysis; variants, vaccination status and previous exposure to the virus, all contribute in the likelihood of progression to ARDS. For that reason, it is of course complex to accurately predict the likelihood for the general population, on average 20%, has been reported in several publications, not only the 2020 paper cited. The most important point we both want to get across, is that, it is highly prevalent in progression to critical illness, in the general population, increasing in those with certain risk factors.

      3. Yes, I agree, given the rapid review protocols and open access fee waivers, a lot of evidence that has been published since the start of the pandemic, in another circumstance may be discredited. There is merit in the papers attempt at condensing the information, at the time of publication, with the volume of evidence, whether weak or poor. I believe the statements conclusion provides enough clarity that the overall opinion is, there is very little evidence for vitamin D and COVID-19. That it is another attempt for vitamin D researchers to stake a claim on high-agenda policy topics, when really we should be focusing on overcoming vitamin D deficiency and that vitamin D supplementation campaigns are largely ineffective.

      4. I disagree, a substantial amount of published research findings for COVID-19, particularly those investigating potential health or lifestyle interventions, have reporting issues. We know this to be the case given the immediate need to inform the scientific community of advances during the pandemic. We need to be open-minded to the evidence we have to date, most of it is weak, and poorly designed, as I conclude, but importunely given the nature of the pandemic, researcher didn’t have much time or opportunity to design gold standard studies, with many making use of retrospective data to the best of their ability. Either way we can see trends evolving. Possibly there is reporting errors, whether it is referred to as a “selection committee”, and triage protocols differed across Spain during the pandemic, or whether it is consultant or clinically led, I think we can take from the paper, that appropriately qualified staff made informed decisions, to the best of their ability, with patients most severely affected by COVID-19, i.e. those with any COVID-19 clinical vulnerability (such as, high blood pressure, diabetes etc). This is a major issue when investigating vitamin D and COVID-19, which is clearly outlined in the statement. The paper was also included as there is a small pool of clinical evidence.

      I am glad you found some of the information useful and I really appreciate that you have taken the time to engage with the statement. Hopefully, that clarifies some points.

      1. Thank you Niamh for the clarifications, really appreciate it.

        Regarding point 4. I agree with you that perfect studies during a pandemic are not possible and reporting errors will happen. I do want to reiterate that this study and the people linked to it are quite problematic. One of the main authors published another vitamin D / covid study and it was retracted due to massive issues on their description of the methodology, the analysis, and question over ethical approval just to name a few. It was a preprint in The Lancet that concluded a 60% reduction in mortality and an 80% reduction in ICU admissions after vitamin D supplementation. This study has been used not just to promote vitamin D as a treatment but also loved by antivaxers and promoters of non-medical indicated cures for covid (like hydroxychloroquine, something they also used in the study).

        That lead author has been on the news talking about how this treatment has saved thousands of lives ( I have seen first hand the damage that studies like this have done in Spain (where the researchers are) and the impact they can have on our fight against the pandemic. Hope you can understand my frustration with studies like this.

  2. Fantastic statement. Thank you. Is there any link between Vit K and D to aid absorption?

    1. Author

      Thank you, Declan.

      Absorption of vitamin D is dependent on a number of important factors, but mainly, sunlight (UVB) exposure, age, body weight, liver and kidney function and gut health. Whereas, vitamin K and vitamin D work together to support calcium metabolism. Some bone health supplements may include a vitamin D and vitamin K complex, as there is evidence that vitamin D supports vitamin K production – therefore optimising calcium levels. I am not aware of any evidence that vitamin K aids the absorption of vitamin D.

  3. Thank you for this article Niahm, very balanced and well pieced. I would also like to quote and ask a few questions as to your information laid out, thanks in advance:

    ‘To this point a set of preventative measures recommended by the WHO to prevent infection and slow transmission endorsed worldwide by most governments and public health agencies, with varying levels of compliance by the general population. Such measures include:…’

    Thank you for putting this part in, I think it holds an incredibly important point for anyone who frequents the site or listens to the podcast. Given the vast majority of readers are interested in lifestyle medicine as it pertains to nutrition, physical activity, higher levels of quality sleep et al. I find it incredibly short-sighted of the government(s) to continually not mention the importance of these situations – I think we could equally make a case for the importance of social wellbeing too and the impact that lockdowns have had on us (particularly where I am, here in Victoria, Australia – I can’t speak for all Australian’s or even all Victorian’s but many suffered enormous psychosocial issues and your link to socioeconomic factors there was very important as it relates to this).

    ‘However, as put by Our World in Data, it is important to note that the case fatality rate “is the ratio between the number of confirmed deaths from the disease and the number of confirmed cases, not total cases. That means that it is not the same as – and, in fast-moving situations like COVID-19, probably not even very close to – the true risk for an infected person.”

    The data point itself makes sense but I would imagine this is confounded inversely as well. The true risk of infection may well be a point of note as you clearly mention, but it should equally be mentioned that there is the likely association of deaths with COVID-19 as contrasted with deaths from COVID-19. To some extent, the very same variables can impact or distort the numbers associated with hospitalisation visits and ICU requirements.

    I agree mostly with your article and your personal conclusions. I have some questions – as Anna does about those two papers – but I am not as concerned about them as she is. I also have some questions about other less favourable papers as well but I think your statement overall holds a strong point without being overtly biased in any one direction. The weight of evidence I have looked at carefully points to it being pretty important to remain sufficient, that’s for sure. And given how many folks are not sufficient, supplementation with, at the price and relative safety that vitamin D is, isn’t a bad idea – especially in the more vulnerable.

    1. Author

      Thank you, Troy.

      These are important points. Yes, whilst in the early stages of the pandemic, rapid response measures were required, there was minimal tailoring of government responses to other forms of vulnerability, or protective measures. This improved to varying degrees, overtime, and across countries and regions but a lot was excluded from consideration. With the many lessons learnt and demonstrated successes of bottom-up approaches, as opposed to top-down governance, we can hope that future pandemic preparedness strategies will incorporate a wider view of physical health and social needs, in addition to the direct effects of the risk in question.

      In regards to the reporting of impact data, such as cases, deaths etc., I agree I think more effort is required in ensuring transparency and standardisation in data collection and reporting, this is heavily dependent on the reporting agency, and the governing bodies. There has been much effort in the EU in regulating the use of public health data, especially given the volume of data generated by the pandemic, a lot is still to be overcome, in terms of misleading reporting and public trust but we can hope that some positive changes can arise, considering the spotlight the pandemic has given to longstanding issues.

      Again, thank you for reading and engaging in the article, it is great to read your feedback.

Leave a Comment