Can vitamin D reduce the risk of COVID-19?
Experts are investigating whether vitamin D deficiency is linked to severe Covid-19 symptoms. Here is a brief overview:
-
Several studies have linked vitamin D deficiency to both coronavirus infections and more severe disease progression in codid-19 disease
-
Scientists are investigating whether vitamin D supplementation could help protect against severe Covid-19 symptoms
-
Even before these studies are completed, there are good reasons to consider using a vitamin D supplement
With no coronavirus vaccine yet available, many people are turning to vitamins and other supplements to protect their immune system and help it keep Covid-19 at bay.
Even though many social media posts tout these supplements as a personal shield, experts like American virologist and director of the National Institute of Allergy and Infectious Diseases Dr. Fauci say that most of these immune-boosting supplements won't do much.
However, there is one supplement that can be beneficial to our immune system - vitamin D, also known as the sunshine vitamin. If you suffer from a vitamin D deficiency, this will affect your susceptibility to infections. For this reason, experts such as Dr. Fauci also recommend taking vitamin D supplements.
Even if these statements are often not made directly in connection with Covid-19, the general role of vitamin D in supporting the immune system and especially its benefits for people suffering from a vitamin D deficiency should not be underestimated.
Although the US Food and Drug Administration says there is no clear evidence yet that vitamin D can protect against Covid-19, there is so much evidence that scientists are intensively investigating the potential benefits of vitamin D and other supplements in relation to coronavirus.
Vitamin D deficiency is associated with COVID-19
Early research has shown that vitamin D can reduce the risk of respiratory infections (which include COVID-19) (1). The benefits varied between these studies, but vitamin D supplementation appeared to be more helpful for those suffering from vitamin D deficiency.
More recent research suggests that vitamin D deficiency may increase the risk of coronavirus infection and worsen the severity of COVID-19 disease.
Dr. Luigi Gennari, a professor in the Department of Medicine and Neuroscience at the University of Sienna in Italy, recently presented data at a meeting of the American Society for Bone and Mineral Research showing a possible relationship between low vitamin D levels and an increased risk of more severe COVID-19 courses.
The American scientist said that people who came to the intensive care unit at Santa Luca Hospital in Milan with severe COVID-19 symptoms had lower 25-hydroxyvitamin D levels and higher interleukin 6 levels (a protein produced in the body in connection with inflammation) than patients who had milder symptoms and did not come to the intensive care unit.
People who died of COVID-19 in this hospital had lower vitamin D levels on average than patients who survived.
Some studies have found, for example, that the number of COVID-19 deaths is higher in countries further away from the equator (2), where many people suffer from a vitamin deficiency due to reduced sun exposure, especially in winter (3).
Our body produces its own vitamin D when the skin is exposed to sunlight and many people can easily develop a deficiency in winter with reduced sun exposure.
While it is possible that other factors may also contribute to the higher COVID-19 case numbers in northern countries, a recent study published in JAMA Network supports the importance of vitamin D for a healthy immune system (4).
"In our study, patients with lower vitamin D levels had a higher risk of testing positive for COVID-19," said study author Dr. David Meltzer of the University of Chicago Medicine.
This trend continued even when the researchers tried to control for other factors such as age, obesity or other medical conditions that can exacerbate COVID-19 disease and are associated with low vitamin D levels.
Other studies show that patients with lower vitamin D levels who have been diagnosed with COVID-19 tend to have a poorer prognosis for disease progression.
One of these studies was recently published in the journal PLoS ONE (5). Researchers found that people who had been hospitalized for COVID-19 and were vitamin D deficient were more likely to develop severe COVID-19 symptoms or die.
However, not all research supports this link between vitamin D and COVID-19. For example, a recent study published in Diabetes & Metabolic Syndrome: Clinical Research & Reviews found no association between vitamin D levels and coronavirus disease (6).
However, Meltzer and his colleagues emphasized in their publication that the authors of the study had carried out the vitamin D levels up to 14 years before the COVID-19 tests and had not asked whether the subjects had been treated with vitamin D in the meantime. This could weaken the observations regarding the undetectable link between vitamin D and COVID-19.
Scientists are also investigating other nutrients as potential treatments for COVID-19, including zinc and vitamin C, which are known for their beneficial properties against the common cold.
In a study from Spain, scientists reported that patients with low zinc blood levels were at higher risk of death from Covid-19 (7).
Studies investigate the benefits of vitamin D
These studies are observational, meaning that scientists collected data from people over time rather than dividing subjects into different treatment groups. This makes it impossible to show a direct cause-and-effect relationship between vitamin D and COVID-19.
The latter requires randomized controlled trials, the "gold standard" of clinical trials, some of which are already being planned or conducted.
In a Spanish study, researchers administered calcifediol - an active form of vitamin D - to 50 patients hospitalized with COVID-19 (8). Another group of 26 patients received no vitamin D.
All patients were treated equally with hydroxychloroquine and azithromycin. Only one of the vitamin D-treated patients ended up in intensive care, while half of the untreated patients ended up in intensive care.
One of the authors of the study concluded: "Our pilot study has shown that the administration of high doses of vitamin D in the form of calcifediol or 25-hydroxyvitamin D can significantly reduce the need for ICU treatment for COVID-19 patients."
While this study has a few limitations - it's not particularly large and there was a slight imbalance between the groups - it's still quite impressive.
While this study used vitamin D to treat people who already had COVID-19, scientists believe that vitamin D could work just as well when it comes to preventing people from being hospitalized in the first place.
One possibility could be that while vitamin D does not prevent COVID-19, it means that people who are infected show such minimal symptoms that they are never tested and the disease goes undiagnosed.
However, further scientific research is needed to find out whether this is actually the case.
Two randomized controlled trials being conducted at the University of Chicago should provide some answers. In both studies, patients are treated with vitamin D and then observed to see if they contract COVID-19 and how severe their symptoms are.
One study focuses on healthcare workers, while the other focuses on "regular citizens" with an emphasis on people of African-American and Hispanic descent who are at increased risk for both vitamin D deficiency and COVID-19.
Scientists at the Cleveland Clinic are looking for volunteers for a study to investigate whether vitamin C or zinc - or a combination of both - can reduce the duration of COVID-19 symptoms. Patients in this study will receive the supplements after testing positive for COVID-19.
Should you use vitamin D supplements?
Even before these studies are completed, there are good reasons to consider taking a vitamin D supplement.
The vast majority of people in our latitudes are vitamin D deficient and could therefore benefit from adequate vitamin D supplementation. In America, for example, an estimated 41% of all adults are vitamin D deficient and in Central Europe the figures are no better (9).
People of darker skin color are at even higher risk, as reflected in the fact that 63% of Hispanics and 82% of African-Americans in America have low vitamin D levels.
Other factors for increased risk of vitamin D deficiency include age, limited sun exposure, obesity and certain medical conditions.
In addition, it is difficult to get vitamin D from food, as even the richest food sources only contain trace amounts of this vitamin.
Zinc can also be helpful if you are experiencing symptoms of an impending cold. In this case, some doctors recommend taking between 12 and 25 mg of zinc every two hours for as long as you experience cold symptoms, but no longer than two weeks.
As with vitamin D, it is not yet 100% known whether zinc can reduce COVID-19 symptoms.
While most people get enough zinc from food, some groups of people such as vegetarians, people with digestive tract conditions and people who abuse alcohol are at higher risk of zinc deficiency and should therefore consider taking a zinc supplement.
A recent meta-analysis of 40 scientific studies concluded that daily, long-term doses of vitamin D protect against acute respiratory infections (10).
How vitamin D helps
Vitamin D plays an important role in keeping us healthy and fighting disease in the least destructive way by regulating the immune response without provoking an immune system overreaction such as a cytokine storm, which is often associated with severe COVID-19 disease.
Vitamin D steers the immune system away from highly inflammatory pathways towards pathways that are more regulated.
Although it is best to get vitamin D from natural sources, supplements can also be effective in supporting the immune system.
Health experts also recommend having your body's vitamin D levels tested by a doctor. In times like these, it's more important than ever to know what's going on in your body. Vitamin D could help prevent COVID-19 from harming you or other people.
References:
- https://www.bmj.com/content/356/bmj.i6583
- https://nutrition.bmj.com/content/early/2020/06/14/bmjnph-2020-000110
- https://www.tandfonline.com/doi/abs/10.3402/ijch.v67i2-3.18258
- https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2770157
- https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0239799
- https://www.sciencedirect.com/science/article/pii/S1871402120301156
- https://www.eurekalert.org/pub_releases/2020-09/esoc-lzl092220.php
- https://www.sciencedirect.com/science/article/pii/S0960076020302764
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6075634/
- https://www.medrxiv.org/content/10.1101/2020.07.14.20152728v1