This article looks at the role food plays in precision medicine and nutrition therapies targeting cancers, specifically the mechanistic role of bioactive phytochemicals and their interaction with tumour progression, metastasis, and chemo-resistance. The term precision medicine represents the advances in genomics, metabolomics, and proteomics which have made cancer treatments more targeted and ‘precise’. Lung, breast, prostate and colon cancers account for a 49.2% mortality rate amongst cancers. Relapses worsen the prognosis of patients. This review aims to provide a better understanding of metabolic variation between nutrients, metabolism, microbiota, and related genes, which may help to develop adjuvant cancer therapies for the above cancers. 35 studies from 2017-2019 were selected: 20 on polyphenols, 3 on lipids (omega 3) and 12 on bioactive plant extracts. Epigallocatechin-gallate (EGCG), a flavonoid present in green tea, is shown to inhibit tumour cell growth. Curcumin modulates gene expression and critical anti-apoptotic effectors and enhances the effect of some targeted drugs used in cancer treatment. Bioactive lipid docosahexaenoic acid (DHA) induces apoptosis and has inhibitory effects on breast cancer cells growth. Ginger is shown to have an antiproliferative impact on cancer cell growth. Grape seed extract was associated with antitumor effect in colon cancer in combination with curcumin. Bioavailability of these extracts is discussed as a barrier to clinical use. Precision nutritional therapies are seen as a new era in the treatment of cancer and precision medicine but the review concludes that more research is necessary.