Olivia Hagen
Graduate Student in Dietetics, Coordinated Program
When coronavirus disease 2019 (COVID-19) turned the world upside down, people were scrambling for any natural solution to keep themselves healthy. Acute respiratory syndrome coronavirus 2 (SARS-CoV-2) leads to COVID-19, and as of October 2022, over 625 million cases have been reported globally. Social media became a sandstorm of health knowledge, claiming supplements and natural remedies were the answer to staying safe from COVID-19 infection. Many people latched onto claims that vitamin D deficiency increased risk for incidence and severity of infection. Whether you’ve heard to spend more time in the sunshine or buy a bottle of supplements, it is no secret that vitamin D, an essential fat-soluble vitamin, is all the rage these days.
While vitamin D is best known for its important role in maintaining bone health, there is a plethora of emerging evidence of this vitamin’s role in immune health, specifically in reducing the risk of acute respiratory tract infections. It did not take long for scientists to dive deep into research on vitamin D’s impact on COVID-19.
One study utilized 8297 subjects from the UK Biobank with COVID-19 test results from 22 testing centers from March 16th, 2020 to June 29th, 2020. Subjects with complete and thorough data on vitamin D supplement use and blood serum vitamin D levels were accepted into the study. Utilizing a questionnaire, participants were interrogated about regular supplement usage and ingredients. The questionnaire also obtained information on each subject’s demographics, social history, dietary patterns, and history of illness, such as presence of hypertension (high blood pressure), diabetes, and cancer.
Researchers used serum vitamin D measurements to categorize each participant as either having a vitamin D deficiency (<25 nmol/L), insufficiency (25-50 nmol/L), or sufficiency (>50 nmol/L). The UK Biobank provided COVID-19 test results, primarily from nose/throat swabs, to measure the primary outcome of the study. Researchers performed statistical analyses to evaluate the association between vitamin D supplement use and the risk of COVID-19.
Results indicate that regardless of lifestyle, disease state, economic status, and category of serum vitamin D levels, continued use of vitamin D supplements is associated with a lower risk of COVID-19 infection.
There are several mechanisms by which the inverse relationship between vitamin D intake and COVID-19 risk is justified. For one, viruses break down the bridges connecting cells, or cell junctions. Vitamin D, however, works to maintain the structure of these junctions. Thus, it is not surprising that vitamin D status impacts the virus’s ability to impair cell “bridge” integrity. Vitamin D also possesses the ability to improve innate immunity, which is the body’s first line of defense against harmful pathogens. This fact paired with vitamin D’s ability to reduce inflammatory immune responses is thought to explain how this powerful vitamin can inhibit COVID-19 from total invasion of the body. One study found that a deficiency in vitamin D increased risk of lung fibrosis, or when the lungs become damaged and scarred through something called the renin-angiotensin system (RAS). SARS-CoV-2 has shown to inhibit RAS from working properly, leading to acute respiratory distress syndrome. Because vitamin D works to help balance RAS, it is a fair assumption that this is another mechanism by which this fat-soluble vitamin fights COVID-19.
While this research found an inverse association between supplemental vitamin D use and COVID-19 infection risk, this study had several limitations to consider. Many people who obtain COVID-19 tests are potentially more inclined to use supplements. Also, these tests were administered in hospitals to patients displaying COVID-19 symptoms. These factors can lead to a potential selection bias, which implies that this data may not be representative of the entire UK or global population. Also, supplement usage is associated with a healthier lifestyle, which may also lower COVID-19 risk.
In conclusion, this study found a promising association of vitamin D supplement use with a decreased risk of COVID-19. This study aligns with other studies that have similar findings of vitamin D’s protective nature against COVID-19. That being said, readers should be cautious to interpret vitamin D as the only factor to reduce infection risk. Obtaining the advantageous and widely available COVID-19 vaccination, along with living healthy lifestyle, consuming a balanced diet rich in nutrient-dense fruits and vegetables, and partaking in regular physical activity will improve overall health and help individuals globally remain healthy throughout this pandemic.