Mediterranean Diet, Redox Biomarkers, and Body Composition in ICU Post-COVID-19 Patients

Background: Post-COVID-19 condition (PCC) remains a public health concern due to persistent metabolic and inflammatory alterations, especially among ICU survivors. Oxidative stress is involved in PCC pathophysiology, and the Mediterranean diet may be associated with redox balance. Objective: To evaluate the association between Mediterranean diet adherence (main exposure variable) and oxidative stress/redox stress biomarkers (primary outcomes) in ICU survivors with persistent symptoms after severe COVID-19. Additionally, body composition and inflammatory markers were explored as secondary outcomes related to redox status. Methods: This cross-sectional study included 123 adult ICU survivors with PCC (51 ± 13.2 years; 53% men; 75% with obesity). Protein carbonyls, TBARS, sulfhydryl groups, glutathione, CRP, albumin, and IL-6 were measured. Diet adherence during post-COVID-19 outpatient follow-up was assessed using MEDAS, and body composition by DXA. Participants were categorized by the median score, and Poisson regression models were applied. Results: The median MEDAS total score was 4 (IQR 2–5), indicating overall low adherence to the Mediterranean diet. Lower adherence was associated with higher glutathione levels (p = 0.04), with no differences in pro-oxidant markers. Higher sulfhydryl levels were associated with lower body fat, higher appendicular skeletal muscle mass, and lower CRP and IL-6. Conclusions: Low adherence was frequent and associated with antioxidant differences. Redox status was also associated with body composition and inflammatory markers.