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.
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.