Selenium

Tier 2 — promising · Thyroid · Antioxidant · Immune

Essential for thyroid hormone conversion and antioxidant defense via glutathione peroxidase. A 2024 meta-analysis confirmed it lowers thyroid autoantibodies (TPO-Ab) in Hashimoto's disease in people who are deficient. Two Brazil nuts daily provide roughly 150–180 mcg. Excess selenium above 400 mcg per day causes toxicity: hair loss, nail brittleness, and nerve damage.

Dose: 55–200 mcg/day selenomethionine; test serum selenium first; do not exceed 400 mcg/day