[CHD note: With the United States largely shut down and the deaths from COVID-19 rising, we wanted to share the following information and questions with our readers.  Please share this widely on social media, particularly with health professionals on the front lines, government officials and anyone who might be interested in studying Vitamin D and coronaviruses.]

Introduction

Briefly, the literature on Vitamin D's role in immune health has exploded in the past 10 years, particularly in relation to viral infections and autoimmune disorders.  Approximately 80% of the literature is new in the past decade and much of it has been published overseas.  There are studies showing that Vitamin D sufficiency is important to reduce mortality in ventilated patients.  There is a large and growing literature on Vitamin D's role in preventing viral infections and reducing their severity.

The populations at highest risk of severe cases of COVID-19 (the elderly and those with underlying health conditions) and the timing of the outbreak (end of winter in the Northern Hemisphere when population Vitamin D levels are typically lowest) are consistent with deficient Vitamin D status being a risk factor for COVID-19.  The relatively small percentage of infections in children may reflect children's higher milk consumption since milk is fortified with Vitamins A and D.  Vitamin D is both a vitamin and a steroid hormone with hundreds of roles in our bodies.

A 2018 study based on NHANES data from 2001-2010 found that 28.9% of American adults were Vitamin D deficient (serum  25(OH)D<20ng/ml)  and an additional 41.4% of American adults were Vitamin D insufficient (serum 25(OH)D between 20ng/ml and 30ng/ml).  Americans who were black, less-educated, poor, obese, current smokers, physically inactive or infrequently consumed milk had higher prevalence of Vitamin D deficiency.  Those with intestinal disorders (Crohn's or celiac) that reduce dietary uptake of Vitamin D and those with liver or kidney diseases that may reduce the body's conversion of Vitamin D to its active form may also be at increased risk of deficiency regardless of age.  Vitamin D is a fat-soluble steroid hormone that regulates over 200 genes in the human body.

Questions that need answers

Based on the breadth of the research on Vitamin D in acute respiratory disorders and the many viral infections in which Vitamin D status plays a role, the following questions need to be answered:

Are hospitalized COVID-19 patients Vitamin D deficient (serum 25(OH)D levels < 20ng/ml) or insufficient (levels between 20ng/ml and 30ng/ml)?

Are hospitalized COVID-19 patients more Vitamin D deficient than would be expected in matched controls?

Are hospitalized COVID-19 patients who need intensive care more Vitamin D deficient?

Does giving high-dose Vitamin D to COVID-19 patients reduce their need for mechanical ventilation and/or reduce the amount of time that they require mechanical ventilation?

Does giving high-dose Vitamin D to health-care workers reduce their risk of COVID-19?

If Vitamin D deficiency is found in severe COVID-19 patients, what recommendation should be made to the general public, particularly those who are quarantined and/or fighting infections at home?

While only time and studies will give us definitive answers to these questions, Vitamin D testing is widely available, supplements are inexpensive and in a COVID-19 critical care setting we should consider anything that might reduce the number of cases, hospitalizations and deaths.  Even a 10% reduction in one of these metrics would have a major impact.

The literature supports the importance of Vitamin D sufficiency

There are studies suggesting that sufficient Vitamin D reduces the risk of acute respiratory infections.  Also, the literature supports the importance of Vitamin D sufficiency in reducing morbidity and mortality in critical care settings.  This is a sample of the literature.