Inflammation plays a great role in the pathogenesis of COVID-19 as a life-threatening epidemic. This study was conducted to investigate relationship between dietary inflammatory index (DII) and severity and symptoms of COVID-19.

In total, 683 patients recovered from COVID-19 were included. Dietary intakes of participants were assessed using a validated 168-item FFQ. Outcomes of interest were including severity of disease, symptoms, hospitalization, hypoxia, need to respiratory support, severe lung infection, disease duration, hospitalization, recovery after hospitalization and respiratory support as well as serum level of CRP and ESR.

Participants at the highest quartile of DII score had higher risk of COVID-19 severity (OR: 1.80; 95% CI: 1.01, 3.20), duration of recovery (OR: 1.74; 95% CI: 1.01, 3.02), hypoxia (OR: 2.04, 95% CI: 1.08–3.83), needs to respiratory support (OR: 3.82; 95% CI: 2.08, 7.03), and long disease duration (OR: 2.63; 95% CI: 1.41, 4.89), and higher levels of CRP and ESR (P-value<0.001). Moreover, risk of COVID-19 symptoms including dyspnea, cough, fever, chills, weakness, myalgia, chest pain, headache, vertigo, sore throat, nausea and vomiting and anorexia was higher among those patients; but no such an association was found for the risk of hospitalization, severe lung infection, hospital duration, duration of respiratory support, blood pressure, pulse rate and respiratory rate.

We found that high DII was associated with greater risk of severe disease, higher levels of serum inflammatory markers and lower life satisfaction in patients with COVID-19. Further, prospective studies are required to confirm our findings.