抗氧化劑在某些情況下防止癌症發生，有時也增加癌症發生。臨床研究表明補充抗氧化劑增加肺癌和前列腺癌的發生和死亡。請看

作者最後的討論，也提到了補充葉酸增加乳腺癌的發生和發展 （與此研究揭示的通路相關）。

ROS can cause oncogenic mutations and activate oncogenic pathways, raising the possibility that treatment with antioxidants could suppress the initiation or progression of some cancers^{28, 35}. Antioxidants or antioxidant enzymes suppress cancer initiation in some contexts^{36, 37, 38} while increasing cancer initiation in other contexts^{15, 16, 17, 39}. Increasing dietary antioxidants has generally not reduced cancer incidence in clinical trials⁴⁰. Dietary supplementation with antioxidants actually increased incidence and death from lung and prostate cancer^{41, 42, 43}. Dietary supplementation with folate promotes the development and progression of breast cancer^{44, 45}. Our results suggest that antioxidants promote disease progression, at least in melanoma, by promoting metastasis.