Vitamin D, the fat-soluble hormone produced in the body when sunlight hits the skin, is responsible not only for bone health but is also believed to help regulate the immune and neuromuscular systems. Vitamin D deficiency has been linked to breast cancer, colon cancer, prostate cancer, heart disease, depression, weight gain and other maladies.1
Research on Vitamin D has exploded in the last ten years, and not only is there a large and growing literature on Vitamin D’s role in reducing the risk of acute respiratory infections and reducing morbidity and mortality in critical care settings,2 but new research confirms a relationship between vitamin D levels and the respiratory illness believed to be caused by the novel coronavirus SARS CoV-2.3 4 5 6 7 8 9
Vitamin D levels correlated with health outcomes in COVID-19 patients
In a study10 published on May 6, researchers reviewed data from 20 European countries. Vitamin D levels are severely low in some aging populations, especially in Spain, Italy and Switzerland, whereas Vitamin D levels were higher in the Nordic countries. The study found a negative correlation between mean levels of Vitamin D and number of cases of COVID-19 and mortality from the new coronavirus.
The authors suggested that Southern European countries have lower levels of vitamin D because of decreased exposure to the sun (because people prefer the shade) and darker skin pigmentation, which decreases Vitamin D synthesis. Northern Europe’s levels are better due to the consumption of cod liver oil, vitamin supplements, and Vitamin D fortification of milk and milk products. Furthermore, they suggested that Vitamin D has a modulating effect on inflammatory cytokines, chemokines, and ACE2, which protects against lung injury.
A small, retrospective observational study11 conducted at Louisiana State University Health Sciences Center found the baseline prevalence of Vitamin D insufficiency (VDI) among ICU patients hospitalized in the intensive care unit (ICU) for any cause is 30 to 40 percent, whereas for patients in ICU units with COVID-19, 84.6 percent had VDI. This is in contrast to only 57.1 percent of the COVID-19 patients hospitalized on general floors testing positive for Vitamin D insufficiency.
Strikingly, 100 percent of ICU patients less than 75 years old had Vitamin D insufficiency. Authors of this study believe their findings also contribute to understanding the racial aspect of health disparities associated with COVID-19 hospitalization and mortality statistics. VDI is highly prevalent in dark-skinned persons: 82.1 percent of African Americans have Vitamin D insufficiency vs. 41.6 percent in the U.S. general population.
In a retrospective study12 of 212 COVID-19 patients in the Philippines published electronically on April 9, 2020, Vitamin D status was significantly associated with severity of COVID-19. In the analysis, 85.5 percent of patients with sufficient Vitamin D had mild cases while 72.8 percent of patients who were deficient in Vitamin D had severe or critical cases.
A retrospective cohort study13 of 780 cases with laboratory-confirmed infection of SARS-CoV-2 in Indonesia revealed that a majority of the death cases were older males with pre-existing conditions and Vitamin D insufficiency. Patients with Vitamin D insufficiency (between 20 and 30 ng/ml) were 12.55 times more likely to die and patients with severe Vitamin D deficiency (<20 ng/ml) were 19.12 times more likely to die than those patients with sufficient levels of Vitamin D. After controlling for age, sex, and comorbidity, Vitamin D status is strongly associated with COVID-19 mortality. When compared to COVID-19 cases with normal Vitamin D status, death was approximately 10.12 times more likely for Vitamin D deficient cases.
Cytokine Storm and COVID-19 Mortality
On Apr. 30, 2020, researchers at Northwestern University pre-published a study14 of the role of Vitamin D in suppressing cytokine storm and associated mortality in COVID-19 patients. Researcher Ali Daneshkhah, PhD, said:
Cytokine storm can severely damage lungs and lead to acute respiratory distress syndrome and death in patients. This is what seems to kill a majority of COVID-19 patients, not the destruction of the lungs by the virus itself. It is the complications from the misdirected fire from the immune system.
Vadim Backman, PhD, and lead researcher on the study, says that not only does Vitamin D enhance our innate immune system, it also prevents our immune system from becoming dangerously overactive. This means that having healthy levels of vitamin D could protect patients against severe complications, including death, from COVID-19. “Our analysis shows that it might be as high as cutting the mortality rate in half,” Backman said. “It will not prevent a patient from contracting the virus, but it may reduce complications and prevent death in those who are infected.”15
Scientists continue to research coronavirus and Vitamin D levels
A research team from the University of Granada in Spain is conducting a ten-week trial of 200 COVID-19 patients.16 The study aims to investigate whether the use of vitamin D as an immune modulator agent induces significant improvements of health status and outcomes in non-severe symptomatic patients infected with COVID-19, as well as prevents COVID-19 health deterioration. The study is expected to end on June 30, 2020.
Many Americans are deficient in Vitamin D
Vitamin D deficiency is a major public health problem worldwide in all age groups, but Vitamin D status deteriorates with age due to decreased sun exposure and the body’s reduced ability to synthesize Vitamin D through the skin. Seventy-five percent of people institutionalized in medical facilities are severely vitamin D deficient.17
A 2018 study using measurements from the National Health and Nutrition Examination Survey (NHANES) from 2001-2010 found that 28.9 percent of American adults were Vitamin D deficient (serum 25(OH)D<20ng/ml) and an additional 41.1 percent were Vitamin D insufficient (serum 25(OH)D between 20ng/ml and 30ng/ml). Adults who were obese, physically inactive, smokers, black, less educated, poor and infrequent consumers of milk had a higher prevalence of Vitamin D deficiency.18
Food sources of vitamin D
Very few foods contain Vitamin D, but fatty fish, such as salmon, tuna, mackerel and fish liver oils, are among the best sources. Beef liver, cheese, egg yolks and some mushrooms also may contain small amounts of Vitamin D.19 In the U.S., some foods like milk are fortified with Vitamin D, and both the U.S. and Canada have mandated fortification of infant formula with Vitamin D.
“The problem is that people simply aren’t eating enough of these nutrients,” says Adrian Gombart, PhD of Oregon State University, and co-author of a study20 on nutrients and the immune system:
Vitamin C has roles in several aspects of immunity, including the growth and function of immune cells and antibody production. Vitamin D receptors on immune cells also affect their function. This means that vitamin D profoundly influences your response to infections.21
Safe sun exposure to maintain Vitamin D levels
Vitamin D from the sun is free, widely available, and the most natural way to get enough Vitamin D. There are two types of ultraviolet (UV) radiation from the sun. UVA is equally present from dawn to dusk in both summer and winter, whereas UVB radiation, which is the only form of sunlight that produces Vitamin D, varies in strength depending on the height of the sun and are most intense at noon. It is thought that exposure of a third of the skin to mid-day sunlight for 10-30 minutes three times a week in the summer is sufficient for most people.22
Michael Holick, MD, professor at Boston University School of Medicine , who is the author of The Vitamin D Solution and The UV Advantage, advocates for safe sun exposure as a way to maintain good vitamin D levels. He explains that, “Exposure to early morning and late afternoon sunlight does not provide any vitamin D but does expose us to UVA radiation which can alter the immune system and increase risk for skin cancer.”23 UVB rays cannot penetrate through glass, so people who work next to sunny windows are still prone to Vitamin D deficiency.24
1 DeNoon DJ. The Truth About Vitamin D: Why You Need Vitamin D. WebMD.
2 Weisman, K. COVID-19 and Vitamin D: Could We Be Missing Something Simple? Children’s Health Defense Apr. 7, 2020.
3 Ilie PC, Stefanescu S, and Smith L. The role of vitamin D in the prevention of coronavirus disease 2019 infection and mortality. Aging Clinical and Experimental Research May 6, 2020.
4 Raharusun P, Priambada S, Budiarti C, Agung E, Budi C. Patterns of COVID-19 Mortality and Vitamin D: An Indonesian Study. SSRN Apr. 26, 2020.
5 Lau FH, Majumder R, et.al. Vitamin D Insufficiency is Prevalent in Severe COVID-19 medRxiv.org Apr. 28, 2020.
6 Grant WB, Lahore H, et.al. Evidence That Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients Mar. 30, 2020.
7 Alipio M. Vitamin D Supplementation Could Possibly Improve Clinical Outcomes of Patients Infected with Coronavirus-2019 (COVID-19), SSRN Apr. 9, 2020.
8 Calder PC, Carr AC, et.al. Optimal Nutritional Status for a Well-Functioning Immune System is an Important Factor to Protect against Viral Infections. Nutrients Apr. 23, 2020.
9 Daneshkhah A, Agrawal V, et.al. The Possible Role of Vitamin D in Suppressing Cytokine Storm and Associated Mortality in COVID-19 Patients. MedRxiv.org Apr. 30, 2020.
11 See Footnote 5.
12 Alipio M. Vitamin D Supplementation Could Possibly Improve Clinical Outcomes of Patients Infected with Coronavirus-2019 (COVID-19). SSRN Apr. 9, 2020.
13 Raharusun P, Priambada S, Budiarti C, Agung E, Budi C. Patterns of COVID-19 Mortality and Vitamin D: An Indonesian Study. SSRN Apr. 26, 2020.
14 See Footnote 9.
15 Vitamin D appears to play a role in COVID-19 mortality rates Northwestern Now May 7, 2020.
16 National Institutes of Health Library of Medicine Vitamin D on Prevention and Treatment of COVID-19 ClinicalTrials.gov.
17 Ilie PC, Stefanescu S, and Smith L. The role of vitamin D in the prevention of coronavirus disease 2019 infection and mortality. Aging Clinical and Experimental Research May 6, 2020.
18 Liu X, Baylin A, Levy P. Vitamin D Deficiency and Insufficiency Among US Adults: Prevalence, Predictors and Clinical Implications. British Journal of Nutrition April 2018; 119(8):928-936.
19 National Institutes of Health Office of Dietary Supplements Vitamin D: Fact Sheet for Health Professionals U.S. Department of Health & Human Services.
20 See Footnote 8.
21 OSU researcher: Vitamins help immune system fight COVID-19 koin.com Apr. 24, 2020.
22 How to Safely Get Vitamin D From Sunlight Healthline.com.
23 Bunn, M. Sun Exposure and Vitamin D—Why You Need to Get Naked at Noon? Markbunn.com.au.
24 See Footnote 22.