Dietary supplements in integrative oncology.

Dietary supplement use is highly prevalent among adults and particularly common among individuals with cancer. Despite this prevalence, oncology providers have ambivalence about endorsing dietary supplements due to important questions regarding safety, interactions, and quality assurance. In the United States and globally, the dietary supplement market has expanded substantially under a regulatory framework established by the Dietary Supplement Health and Education Act (DSHEA), yet the absence of premarket approval contributes to uncertainty and unfamiliarity among oncology providers. Constraints on treatment claims indirectly discourage large-scale clinical research, resulting in an evidence base that is dominated by epidemiologic studies, biomarker investigations, animal models, and trials conducted largely outside the conventional drug development paradigm. Within this context, integrative oncology has focused on selected agents with emerging data, including vitamin D, medicinal mushrooms, milk thistle, and melatonin. These supplements represent the most common categories and are among the most frequently used by individuals diagnosed with cancer. Collectively, these data indicate that selected dietary supplements may contribute to cancer prevention, treatment response, survival, and supportive care outcomes when integrated thoughtfully with standard therapies. This integration must be guided by rigorous quality assurance, individualized risk-benefit assessment, and ongoing research to clarify optimal adjunctive use.