Evidence check: Selen in the context of fatigue

Selenium is an essential trace element that, as part of selenoproteins, plays a key role in antioxidant defense and thyroid hormone metabolism. A deficiency can impair thyroid function, potentially leading to hypothyroidism with symptoms such as fatigue, lethargy, and poor concentration. However, clinically relevant selenium deficiency is uncommon in well-nourished populations, including Central Europe, where dietary intake is usually adequate even in low-soil regions. Evidence linking selenium supplementation to fatigue relief is mixed: individuals with confirmed deficiency may benefit, but supplementation in those with normal levels shows no consistent improvement and carries a risk of toxicity (selenosis) at high doses. Therefore, the evidence for selenium as a direct cause or treatment for fatigue is moderate at best. Blood tests (serum or whole blood) can assess selenium status, but results should be interpreted alongside other potential contributors like iron, vitamin B12, vitamin D, and sleep quality. MyBody-X offers nutrient testing that may include selenium, but these are for informational purposes and not a substitute for medical diagnosis. Persistent fatigue warrants a comprehensive medical evaluation.