What role does Selen play in fatigue?

Selenium is an essential trace mineral required for the synthesis of selenoproteins, which play key roles in antioxidant defense (e.g., glutathione peroxidases) and thyroid hormone metabolism (iodothyronine deiodinases). Selenium deficiency can impair conversion of T4 to active T3, potentially contributing to fatigue, low energy, and brain fog. Additionally, increased oxidative stress and weakened immune function may exacerbate tiredness. However, evidence for a direct causal link between selenium supplementation and fatigue reduction in healthy individuals is limited. Benefits are most clearly seen in people with diagnosed deficiency or specific conditions (e.g., Hashimoto's thyroiditis). In well-nourished individuals, extra selenium does not improve energy and may be toxic in excess. Therefore, blood testing (e.g., serum selenium) is recommended before supplementation. Overall evidence is moderate – human studies exist but lack strong RCTs for general fatigue relief.