The effect of adherence to high-quality dietary pattern on COVID-19 outcomes: A systematic review and meta-analysis

Objective Dietary quality and patterns may influence SARS-CoV-2 infection and outcomes, but scientific data and evidence to support such a role are lacking. Therefore, this meta-analysis aims to elucidate the effect of pre-pandemic diet quality on the risk of COVID-19 infection and hospitalization. Methods PubMed/MEDLINE, CENTRAL, Scopus, and EMBASE were systematically searched for articles published up to 1st September 2022. A systematic review and meta-analysis were performed to calculate each outcome's risk ratio (RR) and 95% confidence interval (CI). Results Five studies including 4,023,663 individuals (3,149,784 high-quality diet individuals and 873,881 controls) were included in the present meta-analysis. The effectiveness of high-quality dietary pattern against SARS-CoV-2 infection and hospitalization was 28% (95% CI 19-36%) and 62% (95% CI 25-80%); respectively. Subgroup analysis based on different levels of diet quality showed no difference between middle and high levels of diet quality in reducing the risk of COVID-19 infection. Interestingly, subgroup analysis based on the different types of high-quality diets and the risk of COVID-19 infection revealed that the effectiveness of plant-based diet against SARS-CoV-2 infection was 50% (95% CI 30-65%); while the effectiveness of Mediterranean diet against SARS-CoV-2 infection was 22% (95% CI 12-31%). Conclusion Adherence to a high-quality dietary pattern is associated with a lower risk of COVID-19 infection and hospitalization. More studies are required to confirm these findings, and future studies should determine the biological mechanisms underlying the association between diet quality and risk of COVID-19 infection.