Study design and participants
We conducted a double-blinded, parallel-group randomized placebo-controlled trial on critically ill patients between June 2018 and August 2019. Critically ill patients were recruited from general ICUs of Emam Reza hospital, Mashhad, northeast of Iran. We obtained patient or surrogate consent in case the patient was unconscious. The inclusion criteria were as follows: age >18 years, and being diagnosed with critical illnesses. The exclusion criteria were as follows: patients with renal or liver disease, patients undergoing dialysis, cancer patients undergoing chemotherapy, pregnant or lactating patients. Patients using antioxidant or anti-inflammatory supplements or multivitamin supplement were also excluded. The study protocol was approved by the Research Ethics Committee of Mashhad University of Medical Sciences (registration code: IR.MUMS.fm.REC.1396.671) and was registered in the Iranian Registry of Clinical Trials (registration code: IRCT 20151108024938N2).