Selenium
The thyroid protector and antioxidant powerhouse. Essential for thyroid hormone activation, glutathione recycling, and immune defense through selenoproteins.
⚙️ Key Selenoproteins
Selenium is incorporated into proteins as selenocysteine. These selenoproteins perform critical functions:
Glutathione Peroxidases (GPx)
Neutralize hydrogen peroxide and lipid peroxides using glutathione. Critical for antioxidant defense.
Thioredoxin Reductases
Regenerate thioredoxin, maintaining cellular redox balance. Essential for DNA synthesis and repair.
Iodothyronine Deiodinases
D1, D2, D3 enzymes convert T4 to T3 (active) or rT3 (inactive). Essential for thyroid hormone activation.
Selenoprotein P
Primary selenium transport protein. Contains 10 selenocysteine residues. Also has antioxidant activity.
🦋 Selenium and Thyroid Health
The thyroid contains more selenium per gram than any other tissue. Selenium is essential for thyroid function:
T4 → T3 Conversion
Deiodinases require selenium. Without it, T4 can't be activated to T3.
Oxidative Protection
GPx protects thyroid from H₂O₂ produced during hormone synthesis.
Autoimmune Support
Selenium supplementation reduces TPO antibodies in Hashimoto's.
Important: If supplementing iodine, ensure adequate selenium first—it protects from oxidative stress.
🥗 Food Sources
Brazil Nuts (Highest)
1-2 nuts provide the entire RDA. Careful—easy to overdose.
Seafood
Tuna, halibut, sardines, shrimp. Ocean provides consistent selenium.
Organ Meats & Eggs
Liver, kidney, and eggs are good sources.
Plant selenium content varies based on soil. Some regions have selenium-deficient soils.
💊 Supplement Forms
Selenomethionine
Organic form. Builds body stores. Most like food selenium.
Sodium Selenite/Selenate
Inorganic. Directly supports selenoprotein synthesis.
Typical dose: 100-200 μg/day. Stay under 400 μg total.
⚠️ Selenium Toxicity (Selenosis)
Early Signs
- • Garlic breath odor
- • Metallic taste
- • GI upset, nausea
Progressive Signs
- • Hair loss
- • Nail brittleness
- • Neurological symptoms
Most common cause: Eating too many Brazil nuts. 6-8 nuts daily can exceed the upper limit.
Metabolic Connections
Thyroid
Deiodinases (D1, D2, D3) require selenium to convert T4 to T3
Glutathione
Glutathione peroxidase needs selenium to recycle glutathione
Iodine
Selenium protects thyroid from oxidative damage during iodine use
Vitamin C
Works synergistically as antioxidant network members
Mercury
Selenium binds mercury, providing some protection from toxicity
Zinc
Both trace minerals essential for immune function