Anticancer Potential of Whey Proteins—A Systematic Review of Bioactivity and Functional Mechanisms

Cancer remains a primary global health concern, with treatment-related side effects and malnutrition posing significant challenges to patient care and recovery. In recent years, there has been growing interest in the therapeutic potential of functional food components, especially whey proteins (WPs), due to their notable antioxidant, immunomodulatory, and anticancer properties. This systematic review explores the effects of WPs across various cancer types and assesses their value as supportive nutritional agents. A thorough literature search was conducted in PubMed, Scopus, and Web of Science databases, identifying 24 relevant studies published between 2000 and 2024. The selection process followed PRISMA guidelines. The evidence, drawn from both laboratory and clinical research, suggests that WPs may exert anticancer effects by inhibiting tumor cell growth, promoting apoptosis, enhancing antioxidant defenses, modulating immune activity, and influencing signaling pathways such as the PI3K/Akt, mTOR, and Wnt/β-catenin pathways. Colorectal, breast, and liver cancers emerged as the most extensively studied types. Additionally, the form of WP used-whether concentrate, isolate, or hydrolysate-appeared to influence both biological activity and clinical outcomes. Clinical findings suggest that WP supplementation may support nutritional status, mitigate the adverse effects of chemotherapy, and enhance the quality of life in cancer patients. While the preclinical data are compelling, further high-quality randomized controlled trials are needed to confirm these benefits and determine optimal use in clinical practice. This review highlights WPs as promising, well-tolerated nutritional agents with potential to enhance current cancer care strategies.