Abstract

Free radical generation increases in inflammatory disorders, trauma, sepsis, and catabolic states. Reactive oxygen species (ROS) play an important role in arachidonic acid metabolism, immune cell activation, and cytokine production. However, they mediate damage to DNA, proteins, and cell membranes by oxidization and lipid peroxidation. Antioxidants are molecules capable of inhibiting the oxidation of other molecules. Enzymatic antioxidants include superoxide dismutase, glutathione peroxidase, and catalase. These antioxidants are dependent on nutrient trace elements such as selenium, copper, zinc, and manganese. Nutrient antioxidants include vitamin C, vitamin E, β-carotene, and cysteine. Critically ill patients requiring nutritional support have impaired antioxidant defenses. Many trials have been conducted on the administration of antioxidant nutrients, trace elements for antioxidant enzyme function, and oxygen radical scavengers to critically ill patients. Very low concentrations of plasma ascorbate occur in patients in shock. The vitamin C requirement for parenteral nutrition is the recommended dose of 100 mg/day, which may be insufficient. Research on the therapeutic use of high-dose vitamin C (500 mg/d?2 g/day) for antioxidant therapy is progressing. The recommended vitamin E requirement is 10 IU/d (9.1 mg/d) for adult parenteral solutions. However, whether this is sufficient to ensure antioxidant activity is controversial. Therapeutic dose of vitamins and other nutrients as antioxidants have not been determined yet, and ROS production is unavoidable. Anti-oxidative systems are critically important for human health; therefore, the imbalance between ROS and anti-oxidants should be normalized. (SMN 2011;2:11-15)

• Keywords: Reactive oxygen species (ROS), Antioxidants