Vitamin C is water-soluble, and probably the most famous of all the vitamins. Even before its discovery in 1932, physicians recognised that there must be a compound in citrus fruits preventing scurvy, a disease that killed as many as 2 million sailors between 1500 and 1800. Later researchers discovered that man, other primates and the guinea pig depend on external sources to cover their Vitamin C requirements. Most other animals are able to synthesise Vitamin C from glucose and galactose in their body. The most prominent role of Vitamin C is its immune stimulating effect, which is important for the defence against infections such as common colds. It also acts as an inhibitor of histamine, a compound that is released during allergic reactions. As a powerful antioxidant it can neutralise harmful free radicals and aids in neutralising pollutants and toxins.

Suh SY, Bae WK, Ahn HY, Choi SE, Jung GC, Yeom CH. Intravenous Vitamin C administration reduces fatigue in office workers: a double-blind randomized controlled trial. 1. Nutr J. 2012 Jan 20;11:7.

BACKGROUND: Studies of the efficacy of Vitamin C treatment for fatigue have yielded inconsistent results. One of the reasons for this inconsistency could be the difference in delivery routes. Therefore, we planned a clinical trial with intravenous Vitamin C administration. METHODS: We evaluated the effect of intravenous Vitamin C on fatigue in office workers. A group of 141 healthy volunteers, aged 20 to 49 years participated in this randomized, double-blind, controlled clinical trial. The trial group received 10 grams of Vitamin C with normal saline intravenously, while the placebo group received normal saline only. Since Vitamin C is a well-known antioxidant, oxidative stress was measured. Fatigue score, oxidative stress, and plasma Vitamin C levels were measured before intervention, and again two hours and one day after intervention. Adverse events were monitored. RESULTS: The fatigue scores measured at two hours after intervention and one day after intervention were significantly different between the two groups (p = 0.004); fatigue scores decreased in the Vitamin C group after two hours and remained lower for one day. Trial also led to higher plasma Vitamin C levels and lower oxidative stress compared to the placebo group (p < 0.001, p < 0.001, respectively). When data analysis was refined by dividing each group into high-baseline and low-baseline subgroups, it was observed that fatigue was reduced in the lower baseline Vitamin C level group after two hours and after one day (p = 0.004). The same did not hold for the higher baseline group (p = 0.206). CONCLUSION: Thus, intravenous Vitamin C reduced fatigue at two hours, and the effect persisted for one day. There were no significant differences in adverse events between two groups. High dose intravenous Vitamin C proved to be safe and effective against fatigue in this study. TRIAL REGISTRATION: The clinical trial registration of this trial is http://ClinicalTrials.govNCT00633581.