Researchers advocate vitamin D supplementation for vulnerable COVID-19 groups

10 Apr 2020 --- Conscious that no single supplement, vitamin or food can treat or prevent COVID-19, global scientists are exploring the role that vitamin D supplementation can play in reducing the risk of respiratory infection, in general. Because vitamin D deficiency (VDD) is associated with increased risk of acute viral respiratory infection, it may offer an extra avenue of increasing resistance, with some researchers now calling for “urgent supplementation” in vulnerable groups. NutritionInsight explores to what extent recent research may present opportunities for the sunshine vitamin.

A recently published review in the Nutrients journal observes that the outbreak occurred in winter in the Northern Hemisphere. “[This is] a time when 25-hydroxyvitamin D (25(OH)D) concentrations are lowest and the number of [COVID-19] cases in the Southern Hemisphere near the end of summer are low.” Vitamin D deficiency has been found to contribute to acute respiratory distress syndrome and case-fatality rates increase with age and with chronic disease comorbidity. Both are associated with lower 25(OH)D concentration.”

Another review, published in The Irish Medical Journal, highlights that the molecular virulence mechanism dipeptidyl peptidase-4 receptor (DPP-4/CD26) binding has been identified in the closely-related COVID-MERS virus. “Human DPP-4/CD26 has recently been shown to interact with the S1 domain of the COVID-19 spike glycoprotein, indicating that it may also be an important virulence factor in COVID-19 infection,” the review highlights. “Critically in this regard, DPP4/CD26 receptor expression has been shown to be significantly reduced in vivo upon correction of VDD.” the paper reads.

The Irish researchers are calling for increased vitamin D supplementation to enhance risk groups' resistance to COVID-19. Therefore, the Irish researchers are calling for “all older adults, hospital inpatients, nursing home residents and other vulnerable groups be urgently supplemented with 20-50µg/d of vitamin D to enhance their resistance to COVID-19.” They advocate for this advice to be “quickly extended” to the general adult population.

Independent assessment of the papers
Unaffiliated with either studies, Dr. Peter Bergman, Senior Physician at the Immunodeficiency Unit of the Karolinska University Hospital, Sweden, tells NutritionInsight that “the data in these review-papers do not support a conclusion that vitamin D will work or can prevent the coronavirus epidemic.”

Ultimately, he affirms that vitamin D will most likely have no effect if given to very sick patients, as the “true” benefit will be in the preventive phase. “Vitamin D could provide some sort of immune-boosting in susceptible individuals. The key elements to prevent the coronavirus pandemic will never be vitamin D, but rather social distancing and quarantine-measures,” he warns.

However, even “the most hardcore critic could not deny” that there is a “solid rationale” to perform studies for vitamin D supplementation in risk-groups, such as elderly and obese people, as well as people with darker skin tones, he maintains. 

“[The papers] make a point that there is mechanistic evidence from in vitro experiments that vitamin D inhibits viral replication for other respiratory viruses. There is epidemiological evidence proving people with viral infections have lower serum levels of vitamin D than controls. There is also some randomized control trial (RCT) support that supplementation can prevent respiratory tract infections (RTIs) caused by other respiratory viruses, such as RS-virus, rhino-virus and influenza,” he comments. 

Dr. Bergman further encourages in vitro testing to observe if vitamin D can prevent viral replication in respiratory epithelial cells or reduce inflammation in the coronavirus-context. In his previous work, he analyzed vitamin D’s protective effect against RTIs, published in PLOS One and investigated how vitamin D supplementation can reduce disease burden in patients with frequent RTIs, published in the British Medical Journal.

“Given the many potential benefits and the few risks, my conclusion is that it would be good advice to follow the Irish paper, which I found most reasonable with regard to dosing. Since vitamin D is cheap, accessible and safe, it could be a good idea to supplement groups at risk,” he emphasizes.

Vitamin D can be found in fatty fish, cow’s milk, egg yolks and sun exposed-mushrooms.Both aforementioned COVID-19-related papers affirm that randomized clinical trials are now direly needed to confirm these hypotheses and substantiate the benefits of micronutrient supplementation against infection. Other micronutrients boasting strong evidence for immune support are vitamin C and zinc. 

Effective supplementation formats
Meeting recommended vitamin D needs may be more challenging to meet in food alone, Yasi Ansari, Registered Dietitian at the Academy of Nutrition and Dietetics, US, tells NutritionInsight. “Vitamin D can be found in fatty fish, such as tuna, salmon and sardines, cow’s milk, egg yolks, sun exposed-mushrooms, in addition to breakfast cereals and 100 percent juices that are fortified with vitamin D. 

Ansari acknowledges that the research to support vitamin D’s role in disease prevention and immune health exists. Nevertheless, she highlights the importance of discussing with a dietitian how individuals’ ability to absorb enough vitamin D may be affected by environmental factors, malabsorption issues, medication use, genetics, metabolism and overall dietary intake. 

The general public should aim to get at least the Recommended Dietary Allowances (RDAs) for vitamin D of ~600 IU per day and ~800 IU for ages 70+, according to the Dietary Guidelines for Americans. “There is research to support adults vitamin D needs to be higher than the RDAs. I recommend meeting at least the RDAs and connecting with a physician to assess deficiency risk and add a supplement if needed,” Ansari asserts.

An example of industry’s take on fortifying foods with vitamin D has recently been evidenced by PLT Health Solutions. The company has received a license from the Natural Health Products (NHP) Directorate of Health Canada to market its Earthlight Whole Food Vitamin D powder as a help to “maintain/support immune health” and “helps with immune function.”

“Although we may not be able to fully prevent or treat an illness, it is still important to focus on daily eating patterns that are nutrient-rich with foods high in vitamins C and D, in addition to healthy lifestyle practices, such as practicing food safety, washing hands, staying active, getting enough sleep and taking care of one’s mental health to help support the immune system,” Ansari concludes.

By Anni Schleicher