Polyphenols—naturally occurring compounds found in foods like fruits, vegetables, tea, and wine—have been studied for their potential to reduce side effects of cancer treatment, such as chemotherapy- or radiotherapy-induced toxicity. Scientific interest in polyphenols arises from their antioxidant, anti-inflammatory, and immunomodulatory properties. Compounds such as curcumin (from turmeric), epigallocatechin gallate (EGCG, from green tea), and resveratrol (from grapes) have been the subjects of clinical and preclinical research.

Several randomized controlled trials and systematic reviews suggest that certain polyphenols may help mitigate specific side effects. For example, oral mucositis (painful inflammation of the mouth lining) is a common complication in cancer patients receiving chemotherapy or radiation. Studies on polyphenol-rich preparations (e.g., green tea, curcumin mouthwash) have shown statistically significant reductions in mucositis severity and duration compared to controls. Some evidence also supports the use of polyphenols in reducing gastrointestinal toxicity and fatigue, though results are more variable and not universally conclusive.

The overall quality of evidence remains moderate, with heterogeneity in study design and polyphenol formulations. However, there is a growing body of clinical research supporting adjunctive use of polyphenols to reduce certain treatment-related side effects, though their use should always be supervised by healthcare professionals due to potential interactions with cancer therapies.