Selenium for Cognitive Function

Research suggests that higher selenium status is associated with better cognitive performance across several observational studies, including cross-sectional analyses of older U.S. adults drawn from NHANES data, where higher dietary and blood selenium levels were linked to improved scores on multiple cognitive tests, with some evidence that these associations may be particularly relevant for individuals with hypertension or those simultaneously exposed to heavy metals like cadmium and lead. Animal and preclinical work adds a plausible biological basis for these findings, pointing to selenium's role in antioxidant defense through selenoproteins and pathways such as Nrf2/GPX4, which may help protect neurons from oxidative stress and injury. However, the evidence is not uniformly positive — a Mendelian randomization study, which uses genetic data to test for causal relationships and is generally considered more resistant to confounding than observational research, found that genetically higher selenium levels were modestly associated with increased Alzheimer's disease risk, directly challenging the interpretation of the observational findings. The overall body of evidence is composed largely of cross-sectional studies, which cannot establish cause and effect, and the mixed signals from genetic causal inference methods mean that whether selenium meaningfully protects cognitive function in humans remains an open question warranting further investigation, particularly from well-designed longitudinal and interventional trials.