Is Vitamin C Beneficial to Patients with CAP?

Community-acquired pneumonia (CAP) is one of the most common causes of morbidity and mortality in elderly and children. Vitamin C is known as a physiological antioxidant, regulating innate immune system in the lung. Vitamin C has been used to prevent and treat CAP. However, the use of vitamin C for preventing and treating CAP has been a subject of controversy. We aim to review the most significant findings about vitamin C supplementation in patients with pneumonia based on literature from the PubMed. First, we reviewed recent advances about the role of oxidative stress in CAP. Oxidative stress is a crucial component of the host defense system and inflammatory response. However, excessive oxidative stress can cause a systemic inflammatory response leading to tissue damage. The degree of oxidative stress has been associated with the severity of CAP. Vitamin C is beneficial to the host defense system by regulating the innate immunity in the lungs. We also discuss the prophylactic use of vitamin C for pneumonia. Vitamin C supplementation decreased the pneumonia risk in patients with vitamin C deficiency. However, it is not beneficial for prophylactic use of vitamin C to prevent pneumonia in the well-nourished population. Finally, we summarize the effect of vitamin C on mechanical ventilation used during respiratory failure. Administration of vitamin C decreases the duration of mechanical ventilation by decreasing oxidative stress.