Potential Anti-Inflammatory and Anti-Fatigue Effects of an Oral Food Supplement in Long COVID Patients

long coronavirus disease (COVID) syndrome leads to chronic inflammatory state onset that can have a multisystem impact and compromise organ function. moreover, long COVID syndrome is often characterized by the presence of chronic fatigue, which affects subjects' daily activities and worsens their quality of life. the aim of our double-blind, placebo-controlled randomized trial (protocol code RS 150.21, approved on 4 November 2021) was to evaluate the beneficial effects of the consumption of 2 cps/day, for two months, of an oral food supplement (OFS), based on echinacea angustifolia, rosehip, propolis, royal jelly and zinc, in long COVID patients, compared to a two-month placebo period. The OFS's vitamin C content was equal to 22.17 mg/g (8.87 mg/capsule). the OFS's total polyphenol content was 43.98 mg/g gallic acid equivalents. at the end of the in vivo study, we highlighted a significant decrease in the inflammatory parameters in the OFS period, compared to the placebo period (neutrophil-to-lymphocyte ratio, p = 0.0455; monocyte to-lymphocyte ratio, p = 0.0005; C-reactive protein, p = 0.0145). Our study also highlighted a significant increase in vitamin D serum values (p = 0.0005) and, at the same time, an improvement in patients' life quality and a reduction in fatigue, monitored by the fatigue severity scale. this study showed the OFS's beneficial effects on the inflammatory state, fatigue and quality of life in long COVID patients.