A week ago a friend sent a news report from May 6, Evidence Supports a Causal Model for Vitamin D in COVID-19 Outcomes. The investigators found a worldwide association between COVID-19 deaths, latitude north of the 30th parallel and presumed vitamin D deficiency. They concluded, “a high level of confidence in a causal beneficial role for Vitamin D is justified”.
The same day the Chieftain headlined a similar report from May 18, Vitamin D levels appear to play a role in COVID-19 mortality rates, with the provocative subheading, Patients with severe deficiency are twice as likely to experience major complications. The authors reported an association between estimates of vitamin D levels in different countries to measurements of inflammation, and to COVID-mortality rates. They concluded, “we see a possible role of Vitamin D in reducing complications attributed to unregulated inflammation and cytokine storm.”
A third study published May 6, The role of vitamin D in the prevention of coronavirus disease 2019 infection and mortality examined the correlation between average vitamin D levels in 20 european countries to morbidity and mortality. They “found significant crude relationships between vitamin D levels and ... mortality caused by this infection”.
There are additional investigations similar to the three above. Are you taking vitamin D yet?
The key is to remember that correlations and associations (above) do not prove causality. For example, there is a strong correlation between the per capita consumption of mozzarella cheese and doctoral degrees awarded in civil engineering (www.tylervigen.com/spurious-correlations). But it is unlikely that force feeding mozzarella to your child will turn her into a civil engineer.
Here are the counterarguments to the studies above.
A May 1st review from the Center for Evidence Based Medicine, Vitamin D: A rapid review of the evidence for treatment or prevention in COVID-19, concluded, “There was no (human) evidence related to vitamin D deficiency predisposing to COVID-19, nor were there studies of supplementation for preventing or treating COVID-19”.
A late May consensus report from 22 European and US scientists BMJ Nutrition, Prevention & Health, Vitamin D and SARS-CoV-2 virus/COVID-19 disease, states, “It is absolutely essential that advice given to the public is evidence-based, accurate and timely; anything less would mislead and has the potential to cause harm.” After reviewing the literature, they conclude, “As a key micronutrient, vitamin D should be given particular focus—not as a ‘magic bullet’ to beat COVID-19, as the scientific evidence base is severely lacking at this time—but rather as part of a healthy lifestyle strategy to ensure that populations are nutritionally in the best possible place”.
What is my take-away from all of this?
First, the frequent appearance of the latest “scientific reports” in news sources, irrespective of quality, does a disservice to science and to the public. Reports of associations between two variables, such as COVID-19 and Vitamin D, if published, should emphasize the study limitations. These reports are most useful to generate hypotheses that can be appropriately tested.
Second, a pithy aphorism worth remembering is, “Absence of evidence is not evidence of absence”. Vitamin D deficiency is common, it is critical for good health and it may yet be shown to have a pivotal role in prevention or treatment of patients with COVID-19 infection.
A search in www.Clinicaltrials.gov identified 24 proposed or ongoing worldwide clinical trials of vitamin D, alone or in combination, for prevention and management of COVID-19 infection. Well designed randomized clinical trials should receive emphasis and not be confused with preliminary reports and association studies that often only confuse.
Finally, medical disinformation is rampant. In my ideal world, high schools would provide all students the critical thinking skills needed to help make informed decisions and to assist them in discussing these issues with their medical care professionals.
Ron Polk lives in rural Lostine and is the editor of Mountain Medicine.