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The phytochemicals compounds found in plants are responsible for their colour, taste, and aroma of many foods. Over and above these attributes, emerging evidence suggests that they protect us from environmental and ingested carcinogens by arming antioxidant enzymes, enhancing DNA repair pathways, reducing chronic inflammation, and directly affecting the biological processes that underlie the fundamental hallmarks of cancer progression and metastasis. It is not a surprise, then, that the World Cancer Research Fund (WCRF) and other academic bodies report that individuals eating phytochemical-rich foods have a lower risk of cancer or relapse after treatments. The debate lies in whether concentrating these into nutritional supplements or topical creams can boost their health attributes without causing significant adverse effects. One notable randomised controlled trial has demonstrated benefits of a polyphenol-rich nutritional supplement for men with prostate cancer, another Randomised Controlled Trial (RCT) used a polyphenolic-rich topical balm to prevent distressing chemotherapy induced nail loss but, considering their potential benefits, there is a shortage of robust RCTs. This international evidence reviews highlights significant RCTs relating to cancer, their probable mechanisms of action and scope for future research.