This review highlights the importance of vitamin C for the immune system and its potential role in the prevention and treatment of infections, particularly in the context of COVID-19.
While an adequate intake of vitamin C is essential for the normal function of the immune system, research shows that supplementation with high doses of vitamin C provides little additional benefit in a well-nourished general population.
However, there are specific subgroups such as older people, diabetics and patients with severe sepsis in which vitamin C can show a stronger modulation of inflammatory processes and oxidative stress.
In the context of COVID-19, vitamin C in the form of intravenous administration is particularly promising. It could reduce inflammatory markers such as interleukin-6 (IL-6), shorten mechanical ventilation time and improve survival rates in severely ill patients with acute respiratory distress syndrome (ARDS).
However, in practice, there is a lack of clear evidence to support routine supplementation for the prevention or treatment of COVID-19. Further clinical trials are needed to confirm the efficacy and safety of vitamin C in these contexts.
Background:
Vitamin C (ascorbic acid) plays a key role in the function of the immune system. It acts as an antioxidant, protects immune cells from oxidative stress and modulates pro-inflammatory cytokines. Its potential effect in the prevention and treatment of respiratory infections such as the common cold has been studied for decades. This paper highlights the historical development of vitamin C as a preventive and therapeutic agent, with a particular focus on its potential application in COVID-19.
Physiological function:
Vitamin C is an essential vitamin that cannot be synthesized by humans. It is preferentially stored in tissues such as the brain, lungs and immune cells. A daily intake of 100-400 mg ensures optimum bioavailability. At higher doses (over 1 g/day), absorption efficiency decreases and excess is excreted in the urine. However, vitamin C levels in plasma drop dramatically during inflammation and infections, indicating increased consumption.
Effect on infections:
Previous studies have shown that vitamin C can reduce the duration and severity of colds by about 8-14%, especially in people under severe physical stress. In patients with pneumonia or severe acute respiratory distress syndrome (ARDS), vitamin C as an intravenous infusion can help modulate the inflammatory response and shorten mechanical ventilation time. Especially in intensive care units, a high dose of vitamin C (200 mg/kg per day) for 4-5 days seems to be beneficial.
COVID-19 and vitamin C:
In the context of the COVID-19 pandemic, vitamin C has been investigated as a possible adjuvant therapy for severe cases. Studies suggest that vitamin C could reduce the “cytokine storm” that leads to organ damage in COVID-19. Intravenously administered vitamin C showed positive effects in initial studies, such as the reduction of inflammatory markers (e.g. IL-6) and a potential improvement in survival rates. However, the evidence remains limited and large-scale controlled trials are needed to provide clear recommendations.
Safety profile and application:
Vitamin C is considered safe, even in high doses. Rare side effects such as stomach problems or kidney stones occur mainly with extremely high oral doses (over 2 g/day). Intravenous doses require medical supervision. Despite its increasing popularity during the COVID-19 pandemic, the routine use of vitamin C as a preventive agent for the general population remains unjustified.
Conclusion:
Vitamin C is a promising candidate for supporting the immune system, particularly in patients at increased risk of infection or severe inflammation. While research indicates positive results in critically ill patients, especially in conjunction with COVID-19, the clinical benefit for general prevention remains limited. Further studies are needed to determine the efficacy, optimal dosage and long-term safety of vitamin C in viral infections.