Selenium for Cancer Risk Reduction

Research suggests that selenium's relationship with cancer risk is complex and highly dependent on baseline selenium status, with multiple reviews and observational studies indicating that the nutrient may play a role in reducing risk for certain cancers — particularly prostate and lung cancer — but that more selenium is not necessarily better. Studies indicate a U-shaped dose-response relationship in which both deficient and excess selenium levels appear counterproductive, a pattern observed in animal models and reflected in human data, and a large randomized controlled trial called SELECT found no cancer-prevention benefit from selenium supplementation and even suggested possible harm in men who already had adequate selenium levels. Mechanistic reviews propose that selenium metabolites may help eliminate DNA-damaged cells and support antioxidant defenses, while observational data from the PLCO screening trial found that food-sourced selenium — as part of a broader antioxidant dietary pattern — was associated with lower lung cancer risk, whereas supplemental selenium was not. Overall, the evidence is mixed across review articles, observational studies, and animal research, with major trial data dampening earlier optimism, and researchers increasingly emphasize that individual baseline selenium status and the specific form of selenium consumed may be critical variables that older studies and trials failed to account for.