Vitamin C is synthesized by almost all animals. However, for humans, it is a vitamin that needs constant replenishment in the diet. While its role as an anti-oxidant and for preventing scurvy have been known for a long time, novel functions and unrecognized associations continue to be identified for this enigmatic molecule. In the past decade, new details have emerged regarding differences in its uptake by oral and intravenous modes. While vitamin C deficiency remains largely unknown and poorly addressed in many segments of the population, novel pharmacological roles for high-dose, intravenous vitamin C in many disease states have now been postulated and investigated. This has shifted its role in health and disease from the long-perceived notion as merely a vitamin and an anti-oxidant to a pleiotropic molecule with a broad anti-inflammatory, epigenetic, and anti-cancer profile.

This Special Issue comprises original research papers and reviews on vitamin C metabolism and function that relate to the following topics: understanding its role in the modulation of inflammation and immunity, therapeutic applications and safety of pharmacological ascorbate in disease, and the emerging role of vitamin C as a pleiotropic modulator of critical care illness and cancer.