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SCORE
Selenium
Thyroid · Antioxidant · Immune
Tier 2 — Promising
What it is
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.
Efficacy
3/5
Safety
3/5
Research
3/5
Onset
2/5
Cost
4/5
Drug-int.
4/5
Dose
55–200 mcg/day selenomethionine; test serum selenium first; do not exceed 400 mcg/day
Time of day & tips
Take with food at any time of day. Do not exceed 200 mcg/day without testing. High-dose vitamin C can reduce selenium absorption — space 2 hours apart if using both.
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