How are Selen and sleep related?

Selenium is an essential trace element that functions as a component of selenoproteins, including glutathione peroxidases (antioxidant defense) and deiodinases (thyroid hormone metabolism). Thyroid hormones regulate circadian rhythms and sleep architecture. Observational studies have reported associations between low selenium status and poor sleep quality, possibly mediated by oxidative stress or melatonin synthesis. However, randomized controlled trials are limited and show inconsistent results. In selenium-replete individuals, supplementation does not appear to improve sleep and may cause toxicity (selenosis) at high doses. The EFSA has set a tolerable upper intake level (UL) of 300 µg/day for adults. Consumer blood tests for selenium are available but should not be used alone to guide sleep interventions. Overall, the evidence for a direct selenium–sleep link is mixed: mechanistic plausibility exists, but robust clinical proof is lacking.