title: Rationale and impact of vitamin C in clinical nutrition.
abstract: OBJECTIVE
  The impact of vitamin C on oxidative stress-related diseases is moderate because of its limited oral bioavailability and rapid clearance. Parenteral administration can increase the benefit of vitamin C supplementation as is evident in critically ill patients. The aim here is to assess recent evidence of the clinical benefit and underlying effects of parenteral vitamin C in conditions of oxidative stress.
  
  
  RESULTS
  In critically ill patients and after severe burns, the rapid restoration of depleted ascorbate levels with high-dose parenteral vitamin C may reduce circulatory shock, fluid requirements and oedema.
  
  
  CONCLUSIONS
  Oxidative stress is associated with reduced ascorbate levels. Ascorbate is particularly effective in protecting the vascular endothelium, which is especially vulnerable to oxidative stress. The restoration of ascorbate levels may have therapeutic effects in diseases involving oxidative stress. The rapid replenishment of ascorbate is of special clinical significance in critically ill patients who experience drastic reductions in ascorbate levels, which may be a causal factor in the development of circulatory shock. Supraphysiological levels of ascorbate, which can only be achieved by the parenteral and not by the oral administration of vitamin C, may facilitate the restoration of vascular function in the critically ill patient.
authors.affiliation: Institute of Physiology, Faculty of Medicine, Philipps University of Marburg, Marburg, Germany.
authors.forename: Gerard P
authors.initials: GP
authors.lastname: McGregor
authors.forename: Hans K
authors.initials: HK
authors.lastname: Biesalski
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage* / Q000378:metabolism; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics; D001682:Biological Availability; D016638:Critical Illness / Q000628:therapy*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology
chemical_list: D000975:Antioxidants; D001205:Ascorbic Acid