Vitamin C (ascorbate) has been investigated for its potential to reduce the side effects of chemotherapy, and its use is primarily supported by scientific inquiry rather than tradition. Preclinical studies and some early-phase clinical trials have suggested that high-dose intravenous vitamin C may help reduce certain chemotherapy-induced toxicities, such as fatigue, nausea, and oxidative stress. The proposed mechanisms include vitamin C’s antioxidant properties, which may protect normal cells from the oxidative damage induced by chemotherapy agents, and its potential to modulate inflammation.

However, the overall quality of evidence is low to moderate. Most studies are small, non-randomized, or lack appropriate controls. Systematic reviews and meta-analyses conclude that while vitamin C is generally safe and well-tolerated, the evidence is insufficient to support its routine use for mitigating chemotherapy side effects. Additionally, concerns have been raised that antioxidants might reduce the efficacy of chemotherapy by protecting cancer cells, though this has not been conclusively demonstrated in clinical settings.

Guidelines from major oncology organizations do not currently recommend vitamin C supplementation as standard supportive care during chemotherapy, except within clinical trials. In summary, there is some emerging scientific evidence for vitamin C’s supportive use during chemotherapy, but large, high-quality randomized controlled trials are needed to establish clear benefit and safety.