Apples and Korean green chili peppers are rich in phytochemicals and recognized for their diverse bioactive properties. Given the potential to enhance these beneficial compounds, this study investigated the effects of mineral supplementation during cultivation on the antioxidant and antiproliferative activities of extracts from both crops. Mineral-enriched cultivation significantly increased the total phenolic and flavonoid contents in both crops, which was accompanied by enhanced DPPH and ABTS radical scavenging activities. Moreover, the mineral-supplemented extracts of Korean green chili pepper activated the Nrf2 signaling pathway and upregulated downstream antioxidant enzymes, including heme oxygenase-1 (HO-1), γ-glutamylcysteine ligase (GCL), and glutathione peroxidase (GPx). Notably, the mineral-supplemented Korean green chili pepper extract significantly suppressed the proliferation of human colorectal cancer cells. These findings suggest that mineral supplementation during cultivation may improve the functional quality of apples and Korean green chili peppers, supporting their potential application in cancer prevention and complementary therapeutic strategies.