Supplementary Antioxidants for Preventing Cancer: Beneficial or Detrimental?

Abstract

The global market for supplementary antioxidants, currently valued at approximately USD 4.88 billion, is projected to double by 2030. Despite this growing investment, the clinical efficacy and safety of these supplements in cancer prevention remain contentious. This review evaluates the evidence for key antioxidant supplements, including beta-carotene, coenzyme Q10, folic acid, glutathione, selenium, vitamin C, vitamin E, and zinc, examining their roles in cancer prevention based on randomized controlled trials, systematic reviews, and experimental studies. While dietary antioxidants consistently show protective effects, supplemental forms often fail to replicate these benefits and, in some cases, increase cancer risk. For instance, beta-carotene and vitamin E are associated with increased cancer incidence in certain populations. Conversely, limited evidence suggests potential benefits of zinc, glutathione, and coenzyme Q10, though further high-quality research is needed. This review underscores the complexity of antioxidant supplementation and emphasizes prioritizing dietary sources for cancer prevention. It calls for rigorous studies to clarify the clinical and molecular impacts of these widely used supplements.