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On his blog, Dr. Joseph Mercola explains the link between Vitamin D and COVID-19. He writes that “there is simply no question that vitamin D optimization is a crucial component of COVID-19 prevention and treatment.” He continues:
In addition to the many studies published during 2020 and 2021, since December 2021, four large systematic meta-analyses1,2 have been published, looking at either vitamin D levels, supplementation or both.
In all cases, the data consistently show that low vitamin D levels raises your risk of COVID while higher baseline levels and/or supplementation lowers all risks by 1.5 to three times.
Therapeutic Role of Vitamin D in COVID
In the first of these four meta-analyses, “Prognostic and Therapeutic Role of Vitamin D in COVID-19: Systematic Review and Meta-Analysis,”3 published December 11, 2021, the researchers sought to determine “the association between vitamin D deficiency/insufficiency and susceptibility to COVID-19, its severity, mortality and role of vitamin D in its treatment.”
A total of 72 observational studies, covering 1,976,099 patients, met the criteria for inclusion. Compared to those with sufficient vitamin D, the odds of developing COVID-19 among those with deficient or insufficient vitamin D levels were 1.46 times higher.
Their risk of severe disease was also 1.9 times higher, and their risk of death 2.07 times higher. One potential drawback was that all studies ranked “high” for risk of bias. The studies also differed in their definitions of severe illness and vitamin D deficiency/insufficiency, making absolute comparisons difficult. That said, the authors concluded:4
“Multiple observational studies involving nearly two million adults suggest vitamin D deficiency/insufficiency increases susceptibility to COVID-19 and severe COVID-19, although with a high risk of bias and heterogeneity. Association with mortality was less robust.”
Vitamin D Status and Clinical Outcomes
In the second study, “Vitamin D Status and SARS-CoV-2 Infection and COVID-19 Clinical Outcomes,”5 published December 22, 2021, the researchers assessed “whether vitamin D status is associated with the COVID-19 severity, defined as ARDS requiring admission to intensive care unit (ICU) or mortality (primary endpoints) and with the susceptibility to SARS-CoV-2 and COVID-19-related hospitalization (secondary endpoints).”
Here, they included 54 observational studies (1,403,715 patients) that measured the association between vitamin D status and risk of COVID infection, hospitalization, ICU admission and death during hospitalization. The measures for vitamin D status were as follows:
- Insufficiency — less than 75 nmol/L (30 ng/mL)
- Deficiency — less than 50 nmol/L (20 ng/mL)
- Severe deficiency — less than 25 nmol/L (10 ng/mL)
Seventeen studies reported the association between vitamin D status and SARS-CoV-2 infection; nine reported the association with COVID-19 related hospitalization, 27 reported COVID-19-related ICU admission, and 35 reported COVID-19 related mortality. In summary, the odds of ICU admission based on vitamin D status were as follows:
- Severe deficiency — 2.63 times higher
- Deficiency — 2.16 times higher
- Insufficiency — 2.83 times higher
Those with severe deficiency were also 1.68 times more likely to test positive; those with deficiency were 1.83 times more likely to test positive; and those with insufficiency were 1.49 times more likely to test positive. In conclusion, the authors stated:6
“Patients with low vitamin D levels present an increased risk of ARDS requiring admission to intensive care unit (ICU) or mortality due to SARS-CoV-2 infection and a higher susceptibility to SARS-CoV-2 infection and related hospitalization.”
The Effect of Vitamin D Supplementation
The third study, “The Effect of Vitamin D Supplementation on Mortality and Intensive Care Unit Admission of COVID-19 Patients. A Systematic Review, Meta-Analysis and Meta-Regression,”7 was published in May 2022.
Six studies, involving 860 patients, had data on ICU admission. Of those 860 patients, 369 received vitamin D supplementation and 491 did not, and the effect of vitamin D supplementation was found to be quite significant — 12.19% of patients who received vitamin D required ICU admission, compared to 26.27% of those who did not get vitamin D.
The data in all six studies strongly favored vitamin D. The ideal dose, however, remains uncertain, as no linear relationship between dose and odds ratio of ICU admission was observed.
Vitamin D and SARS-CoV-2 Infection, Severity and Mortality
The fourth and most recent study, “Vitamin D and SARS-CoV-2 Infection, Severity and Mortality: A Systematic Review and Meta-Analysis,”8 was published July 6, 2022, in PLOS ONE.
Here, they looked at COVID-19 in relation both to baseline vitamin D status and supplementation. Thirty-eight studies — including two randomized controlled trials — were included that had risk estimates for at least one endpoint (risk of infection, severity and/or mortality). In all, data on vitamin D status was available for 205,565 patients and 2,022 who were given vitamin D supplementation. According to the authors:9
“Random effects models showed that supplementation was associated with a significant lower risk of both COVID-19 severe disease (SRR 0.38, 95% CI 0.20-0.72, 6 studies) and mortality (SRR 0.35, 95% CI 0.17-0.70, 8 studies).
There were no statistically significant dose differences between studies: summary estimates with regular doses remain statistically significant, suggesting that higher doses are not necessary. For patients on vitamin D supplementation, a greater reduction in mortality risk emerged in older individuals and at higher latitudes.
Regarding the quality of studies, assessed using the New Castle-Ottawa quality scale, the analysis revealed in most cases no statistically significant differences between low, medium or high quality studies.
We found significant associations of vitamin D supplementation with COVID-19, encompassing risks of disease worsening and mortality, especially in seasons characterized by 25OHD deficiency and with not severe patients.”
Why Randomized Controlled Trials Are Not Required
As noted by in a Twitter thread by Karl Pfleger, Ph.D., the data clearly show vitamin D is strongly correlated with all COVID-19 risks, and we do not actually need randomized controlled trials to draw this conclusion:10
“Most underlying studies are observational, but at the very least knowledge of whether someone supplements D or of their D status is strongly predictive of their COVID risks/outcomes. As I’ve noted previously, RCTs are not required for this conclusion to be sound & unquestionable. This establishes a risk factor & most other well known COVID risks factors are also based entirely on observational data.
The data showing age, above-normal-weight, & comorbidities are significant risk factors is also based entirely on correlation. No RCTs establish these as risk factors but no one questions that they are. VDD [vitamin D deficiency] should be thought of as another comorbidity, just like diabetes.”
Indeed, at this point, the importance of vitamin D in the fight against COVID ought to be common knowledge everywhere, especially in health care circles. Yet the surgeon general of Florida, Joseph Ladapo, is the only public health official who is actually recommending vitamin D optimization for COVID.11
This is crazy, as the effects of vitamin D were evident very early on in the pandemic. I launched an information campaign about vitamin D back in June 2020, which included the release of a downloadable scientific report that detailed the science behind vitamin D. This report, as well as a two-minute COVID risk quiz is available on StopCovidCold.com.
In December 2020, more than 100 doctors, scientists, Ph.D.’s and leading authorities from 33 countries also signed an open letter12 to the governments and health officials of the world, calling for the use of vitamin D against COVID. Since then, the list of signatories has grown to 220.
The letter recommended taking enough vitamin D to achieve a blood level of at least 30 ng/mL (75 nmol/L), urged testing of all hospitalized COVID-19 patients and adding vitamin D to the treatment protocol for any patient whose level was below 30 ng/mL.
Not only did health agencies roundly ignore this sound advice, but they also publicly tried to discredit the notion that vitamin D could have any benefit at all, and attacked anyone sharing the good news about vitamin D.
As just one example, in the summer of 2020, the Center for Science in the Public Interest (CSPI), a self-proclaimed consumer advocacy group bankrolled by the Rockefeller Foundation, among others, launched a campaign against Mercola.com. The CSPI falsely accused me of “profiteering from the pandemic” by selling nutritional supplements, including vitamin D, while sharing scientific truth about its benefits.
The campaign culminated in a warning letter from the U.S. Food and Drug Administration, in which they warned me to stop talking about vitamin D. I reviewed this censorship attempt in “Why Is Info on COVID and Vitamin D Deficiency Suppressed?”
The fact of the matter is, data show vitamin D supplementation lowers your risk of a positive test, speeds viral clearance, slows the spread of infection, and lowers your risk of severe infection, hospitalization and death, as summarized in “Vitamin D Deficiency and COVID-19 Severity” and many other articles.
Read more from Mercola here.
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