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Exploring Immune System Benefits of Vitamin D

Vitamin D and COVID-19: Exploring Immune System Benefits of a Vital Nutrient

June 24, 2022
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As scientists, there is nothing we can say with absolute certainty. However, what is safe to assume is that uncertainty around the state of the COVID-19 pandemic will remain for some time to come.

The latest report from the World Health Organization (WHO) indicates that confirmed COVID-19 cases globally are declining. However, public health experts still caution that as testing strategies evolve and countries loosen restrictions like mask mandates, those figures could rise again. Against this backdrop—and as much of the world enters the spring and summer months—it is an ideal moment to rethink and refocus on health and wellness.

While known commonly as an anti-inflammatory, an antioxidant, and for its neuroprotective properties, vitamin D is also garnering attention for supporting immune health. In the blog below, we explore a few of the more common questions around vitamin D and its contributions to human health—including what link it may have in preventing or treating the effects of COVID-19.

What role does vitamin D play in human health?

Vitamin D regulates mineral metabolism, bone growth, and the innate and adaptive immune system.1,2 Because of its role in the immune system, vitamin D can inhibit viral replication and stimulate other immune responses to combat infections.3 Studies have shown that vitamin D plays a role in preventing respiratory infections.4-7 Therefore, it is being speculated that taking vitamin D as a supplement may aid in the prevention or treatment of severe COVID-19.

How do you build immunity against COVID-19?

When discussing potential immunity to any invading pathogen in the body, including SARS-CoV-2, one must understand that two immune responses can occur in the body: innate response and adaptive response.

The innate response represents our body’s first line of defense against pathogens (like bacteria and viruses). This immune response includes barriers (like our skin, tears, mucus, etc.) and various cells and molecules (macrophages) that are meant to respond rapidly to changes in our bodies.

The adaptive immune response (B cell humoral immunity and T cell cellular immunity) target and kill specific cells infected by viruses and produces antibodies to ward off any future infections. Our immunity essentially comes from this immune response.8

Our adaptive immune system can be triggered actively (acquired and vaccine-mediated)1 and/or passively (in utero and/or at birth).9  This same immune response is thought to occur in individuals previously infected with SARS-CoV-2 or individuals who have received the vaccine. For this reason, vaccination is critical to building immunity against COVID-19. In addition to getting vaccinated, it is very important to maintain a healthy lifestyle to strengthen our immune system.

According to the WHO, “while no foods or dietary supplements can prevent or cure COVID-19 infection, healthy diets are important for supporting immune systems.”10 Therefore, it is crucial to incorporate good nutrition because it can reduce the likelihood of developing other health problems, including obesity, heart disease, diabetes, and certain forms of cancer – all of which contribute to co-morbidities in many COVID-19 related complications.

Could taking vitamin D help to prevent or treat COVID-19?

There is insufficient evidence to recommend vitamin D treatment for COVID-19.11 More research is needed to determine the efficacy of vitamin D as a treatment or preventative measure for severe COVID-19. It is also important to keep in mind that vitamin D toxicity is also a possibility.12 As a result, instead of a single dose, efficacy studies should include daily low doses.

Does vitamin D deficiency make COVID worse?

A deficiency in vitamin D has been linked to an increased risk of contracting influenza and respiratory viruses. Studies have shown low serum vitamin D levels among hospitalized COVID-19 patients have also been linked to increased disease severity and poorer clinical outcomes.13-16

A low level of serum vitamin D measured during the acute COVID-19 infection, on the other hand, could be a result of chronic inflammation rather than an underlying cause. Therefore, we are yet to understand if it is true that vitamin D levels drop during active SARS-CoV-2 infection, or that having low vitamin D levels makes the disease worse.

Some studies have suggested that low vitamin D levels upon admission are a predictor of poorer COVID-19 disease outcomes.17,18 Furthermore, a more recent study found a link between low vitamin D levels before COVID-19 infection and increased disease severity and mortality during hospitalization.13 Overall, more research is needed to determine what role, if any, vitamin D supplement and vitamin D deficiency may play in preventing and treating COVID-19.


Maite Sabalza, PhD and Chibuike Ezeibe, MD of EUROIMMUN US, a PerkinElmer Company


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