Evidence check: Selen in the context of longevity

Selenium is an essential trace element that, as a component of selenoproteins (e.g., glutathione peroxidases), plays a key role in antioxidant defense and thyroid function. In the context of longevity, selenium is often linked to reduced oxidative stress and slower cellular aging. However, the evidence is nuanced: observational studies show a U‑shaped relationship between selenium levels and mortality – both deficiency and excess (e.g., from uncontrolled supplementation) can be harmful. Randomized controlled trials on selenium alone for life extension do not provide clear evidence. The effect strongly depends on baseline status, genetic variants (e.g., in SELENOP), and dietary source. For healthy adults with adequate intake (e.g., from nuts, fish, eggs), additional supplementation likely offers no benefit and carries risks (selenosis). Therefore, individual status assessment (blood/serum) before supplementation is recommended. Overall, the evidence for selenium as a longevity supplement is moderate and predominantly mechanistic/observational.