BackgroundThe coronavirus disease 2019 (COVID-19) pandemic has been shown to affect nutritional recommendations. Some functional foods have been demonstrated to be useful in the treatment of people with COVID-19. However, little is known about the impact of combining functional foods on disease control. This study aimed to investigate the effects of functional foods mixture on serum levels of inflammatory cytokines and biochemical findings in patients with COVID-19.MethodsA randomized double-blind controlled trial was conducted in Baqiyatallah Al-Azam hospital in Tehran, Iran. Sixty patients were randomly assigned to receive either a soup containing functional foods (n= 30) or a usual soup (control group) (n= 30). Participants’ sociodemographic information was gathered using a general questionnaire. Blood levels of inflammatory markers and biochemical findings were assessed using standard protocols.ResultsThe results showed that soup containing functional foods was more effective in controlling serum levels of D-dimer, blood urea nitrogen, and creatinine than the control group (P< 0.05). Also, more significant improvement was found in the intervention group vs control group in terms of interleukin (IL)-1β, IL-6, IL-17, IL-10, and tumor necrose factor-α (P< 0.05). In contrast, the control intervention more efficiently controlled potassium levels and reduced quantitative C-reactive protein than the intervention group (P< 0.05).ConclusionsThis study indicates a soup containing functional foods could alleviate biomarkers of inflammation in patients with COVID-19. However, its effectiveness on biochemical findings remained inconclusive which warranted further research.Trial registrationIRCT, IRCT20180201038585N11. Registered 23 August 2021,https://www.irct.ir/trial/57338