A recent meta-analysis of 25 clinical trials located in 15 countries conducted by the UK National Health Service (NHS), Institute for Health Research, indicated that vitamin D supplements reduced the risk of acute respiratory infection (ARI) from 42% to 39% overall. In those with the lowest vitamin D levels regular supplementation reduced the risk from 60% to 32%. Any specific protective effect against COVID-19 is unknown.
Jill P. Pell and Naveed Sattar of University of Glasgow, UK jointly led a study which hypothesised that blood 25 hydroxyvitamin D (25(OH)D) concentration was associated with COVID-19 risk among the UK Biobank participants. 348,598 UK Biobank participants had full data on (25(OH)D) concentration. Within this category 449 had a positive COVID-19 test. The results were published in the journal Diabetes & Metabolic Syndrome: Clinical Research & Reviews.
It was found that median 25(OH)D concentration measured at recruitment was lower in patients who subsequently had confirmed COVID-19 infection (28.7 (IQR 10.0-43.8) nmol/L) than other participants (32.7 (IQR 10.0-47.2) nmol/L. Vitamin D status did not predict COVID-19 infection after adjustment for covariates.
Logistic regression showed that black ethnicity and South Asian ethnicity were both associated with confirmed COVID-19 infection univariably, but there was no significant interaction between ethnicity and vitamin D deficiency.
The study replicated findings that COVID-19 risk was associated with ethnic minorities, men, and those overweight, but did not find association with diabetes or blood pressure.
The study was relatively low powered with only 449 COVID-19 positive individuals. A potentially severe limitation is that vitamin D levels were determined ten years prior to the COVID-19 diagnosis.
“Our study is the first to assess whether there is an association between blood 25(OH)D concentration and COVID-19 risk. We found no such link, suggesting that measurement of 25(OH)D would not be useful to assess risk in clinical practice. Furthermore, our results suggest that vitamin D is unlikely to be the underlying mechanism for the higher risk observed in black and minority ethnic individuals and vitamin D supplements are unlikely to provide an effective intervention,” concluded the authors.