Research suggests importance of vitamin D for good health in the context of COVID-19

As the coronavirus disease (COVID-19) pandemic continues to spread globally, proactive measures to reduce the risk of infection are vital since there is still no approved vaccine to block severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nor drug approved for the safe treatment of COVID-19 disease.

Vitamin D deficiency has been tied to developing severe COVID-19. Correcting deficiency vitamin D status may be a good target in the battle against the pandemic.

A researcher at the UNC Nutrition Research Institute, University of North Carolina revealed that avoiding vitamin D deficiency may help reduce the risk of severe COVID-19.

Further, older, obese, and dark-skinned people are likely to need extra vitamin D, especially during the dark months of winter and spring.

Study: Avoidance of vitamin D deficiency to slow the COVID-19 pandemic. Image Credit: Alrandir / Shutterstock
Study: Avoidance of vitamin D deficiency to slow the COVID-19 pandemic. Image Credit: Alrandir / Shutterstock

Vitamin D deficiency and COVID-19

The SARS-CoV-2 outbreak first emerged in Wuhan City, China, in late December 2019. From there, it has spread to over 191 countries and territories. At present, more than 62.6 million individuals globally have been infected, with over 1.45 million lives lost.

The current study published in the BMJ Nutrition, Prevention, and Health, highlights the factors that can influence vitamin D status and how these are related to COVID-19.

Recent studies have shown the benefit of vitamin D in fighting respiratory infections. The active vitamin D metabolite, 1,25-dihydroxyvitamin D (1,25D), is produced in immune cells and triggers the expression of several genes tied to a healthy immune response.

The metabolite is also linked to the maturation and recruitment of macrophages, increased production of cathelicidin and other antibacterial peptides, and phagocytosis promotion.

However, in some areas worldwide, especially in places at a latitude greater than 40° and includes the United Kingdom, Central and Northern Europe, Canada and the northern half of the United States, and similarly some regions in the southern hemisphere, vitamin D deficiency is a common problem during the winter and spring seasons.

People with low vitamin D status are more likely to develop respiratory infections. Hence, amid the coronavirus pandemic, health experts believe boosting vitamin D levels is crucial to avert contracting COVID-19.

Further, a recent editorial noted that countries below the latitude of 35° North and across the southern hemisphere appear to have lower COVID-19 mortality rates than countries further to the North. The study author believes that a lower capacity to produce vitamin D at higher northern latitudes impairs vitamin D status during the cold season, contributing to high mortality rates.

Key modulators of vitamin D status

Several factors can influence vitamin D status. First, dietary intake plays a significant role in determining one's vitamin D status. Only a few foods, mainly fatty coldwater fish such as sardines, herring, mackerel, and salmon, contain naturally significant amounts of vitamin D.

Some doctors recommend vitamin D3 supplementation to boost vitamin D levels in the body. From the diet, most people get no more than very modest amounts of vitamin D.

Another key modulator of vitamin D status is ultraviolet B (UVB) light exposure. Most of the vitamin D in blood comes from skin exposure to ultraviolet light with wavelengths between 280 and 313 nm, commonly called ultraviolet B (UVB).

Getting adequate exposure to the sun will help boost vitamin D levels. However, spending too much time indoors, prolonged cloud cover, severe air pollution, covering skin with garments, and sunscreen can limit vitamin D production in the skin.

Aging can also affect how much vitamin D a person has in the body. Older age can lead to a lower vitamin D status. Older adults have progressive skin thinning, decreasing the amount of the 7-dehydrocholesterol precursor available for vitamin D conversion.

People who have excess weight may also suffer from low vitamin D status. In one study, the scientists found that the resulting decreased vitamin D status is reversible when excess weight is shed.

Further, some genetic variations may also influence vitamin D status. For example, skin tone can affect the body's capacity to produce vitamin D in the skin. In a study, nearly all non-Hispanic blacks and most Mexican-Americans had vitamin D insufficiency.

"Now, in the context of the current COVID-19 pandemic, renewed attention to the very high prevalence of severe vitamin D deficiency there and elsewhere is in order," the researcher concluded in the study.

"Advanced age, obesity, dark skin tone, and risk-related genotypes, particularly in combination, are alarm signs that should prompt corrective action, typically with a moderate, individually tailored dose of supplemental vitamin D," he added.

The study author emphasizes that while vitamin D supplements' preventive potential should not be exaggerated, preventing vitamin D deficiency should be a widely shared goal. Since COVID-19 severity has also been associated with low vitamin D status, it is crucial for people who are at high-risk to monitor their vitamin D levels.

Journal reference:
Angela Betsaida B. Laguipo

Written by

Angela Betsaida B. Laguipo

Angela is a nurse by profession and a writer by heart. She graduated with honors (Cum Laude) for her Bachelor of Nursing degree at the University of Baguio, Philippines. She is currently completing her Master's Degree where she specialized in Maternal and Child Nursing and worked as a clinical instructor and educator in the School of Nursing at the University of Baguio.


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  1. John Lambiase John Lambiase United States says:

    It is all good to say do not be deficient, but what does it take to get out of deficiency.  

    This last month the UK said they would offer to supplement those who might have the highest potential to be vitamin D deficient.  Their plan is to offer 10 mcg (400 iu) of Vitamin D daily to this group of people, but the question begs to be asked.  Is that enough?  What do the vitamin D experts say?  

    The data does not only suggest much higher supplementation, it points out very explicitly,
    "As noted in the Results section, 12.5 μg/d is the approximate oral input required to maintain serum 25(OH)D at zero change, at least from starting values in the range we observed (≈70 nmol/L). I" (1)

    So according to the study, the 10 mcgs being offered by the UK to those who may be deficient, is not even enough to keep these individuals where they are.  The Study also goes on and talks about safety of high dose daily supplementation.  So if you are replete(sufficient)(≈70 nmol/L*) in vitamin D you have to take in 12.5 mcg's per day just to keep current stores up.  What does this say about those who are deficient?   That 10mcg is not helpful, and might even be harmful by giving people a false sense of security.

    *I think it is important to point out that 70-nmol/L is by no means a full replete state for the potential benefits needed for the immune system signaling at point of attack.(2)

    "Sufficiency is defined as 25OHD3 levels above 30-100 ng/ml (75-250 nmol/l). Levels of 10-30 ng/ml (25-75 nmol/l) indicate insufficiency, those below 10 ng/ml (25 nmol/l) clear-cut deficiency. Therapy is equally easy. Cholecalciferol can be applied orally, and continuous daily substitution is recommended. The therapeutic dose ranges from 4,000 to 10,000 IU (100-250 μg)/day."(2)

    But please do not take my word for it.  Read it here.

    1. Robert P Heaney, K Michael Davies, Tai C Chen, Michael F Holick, M Janet Barger-Lux, Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol, The American Journal of Clinical Nutrition, Volume 77, Issue 1, January 2003, Pages 204–210,

    2. Höck AD. Review: Vitamin D3 deficiency results in dysfunctions of immunity with severe fatigue and depression in a variety of diseases. In Vivo. 2014 Jan-Feb;28(1):133-45. PMID: 24425848.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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