A meta-analysis including 11 321 participants concludes that vitamin D supplementation can help prevent respiratory tract infections.
Respiratory tract infections are the source of over 5 million deaths each year globally, and are responsible for 10% of emergency room visits in the United States.
In recent weeks, a new coronavirus disease called COVID-19 has spread rapidly from where it was first detected in China to many other countries. The symptoms of coronavirus include coughing, fever, and shortness of breath.
Current prevention measures include frequent hand-washing, social distance, and maintaining proper cough/sneeze etiquette.
When it comes to colds and flu, vitamin C is one of the most common supplements employed to help the body ward off infection; however, previous studies have reported an association between low serum vitamin D levels with an increased susceptibility to respiratory tract infection. The vitamin D metabolite 25-hydroxyvitamin D supports the production of antimicrobial peptides in response to both viral and bacterial stimuli allowing protection against acute respiratory infection.
Researchers at the Blizzard Institute in London set out to evaluate the efficacy of vitamin D supplementation on protecting against respiratory tract infections. Their meta-analysis of 15 primary trials reported statistically significant heterogeneity between trials. Several reasons could account for this heterogeneity, such as differences in dosing between trials, which can modify the effects of vitamin D on immunity to respiratory pathogens.
Their study found that regular doses of vitamin D (daily and weekly) were effective in protecting participants from respiratory tract infections. Protective effects were not observed in participants receiving bolus doses. Finally, protective effects from vitamin D were stronger in patients that were vitamin D deficient (<25 nmol/L).
The authors concluded that:
Our results add to the body of evidence supporting the introduction of public health measures such as food fortification to improve vitamin D status, particularly in settings where profound vitamin D deficiency is common.
These results suggest that regular vitamin D supplementation may be a promising addition to our prevention methods to avoid COVID-19 infection, especially in those with a vitamin D deficiency.