Vitamin C administration during malaria infection may have detrimental effects in malaria. Results from an experimental study has shown that concurrent administration of artemisinin and ascorbic acid( vitamin c) compromised the rates of parasite clearance in Plasmodium berghei malaria infection in mice. The effect was more pronounced at higher doses of ascorbic acid which itself could inhibit growth of malaria parasite. Please read the attached document for more details. Hope this helps and good luck
It is an interesting question. There is actually not clear-cut evidence in human about this. Nevertheless, ascorbic acid has chelating and reducing properties which greatly enhances the absorption of (non-heme) iron from dietary intake. The interaction between iron and malaria is very complex and to my knowledge enhanced iron absorption or supplementation has shown conflicting results in different studies in malaria and malaria susceptibility. Effects in animal models, as mentioned in the other reply, are extremely difficult to extrapolate to human and human data are to my knowledge largely lacking, but it is probable that high-dose vitamin C supplementation could actually have a negative effect on parasite clearance - however the effect on mortality in severe malaria might be the opposite as anemia can be one of the driving factors in this.