Selenium
Selenium (Se)
Moderate
Selenium is a trace mineral that functions primarily through selenoproteins—antioxidant enzymes including glutathione peroxidases. It is essential for thyroid hormone metabolism, immune function, and protection against oxidative stress. Brazil nuts are an especially rich natural source.
How It Works
Selenium functions through selenoproteins:
- Glutathione Peroxidases (GPx): Family of antioxidant enzymes that neutralize hydrogen peroxide and lipid peroxides using glutathione.
- Thioredoxin Reductases: Regenerate thioredoxin, an important cellular antioxidant.
- Iodothyronine Deiodinases: Convert T4 to active T3 thyroid hormone. Selenium deficiency impairs thyroid function.
- Selenoprotein P: Transport protein that delivers selenium to tissues; also has antioxidant properties.
- Immune Function: Supports T-cell and natural killer cell function.
Natural Food Sources
| Food | Amount per Serving |
|---|---|
| Brazil nuts | 544 mcg per 1 oz (6-8 nuts) |
| Yellowfin tuna | 92 mcg per 3 oz |
| Yellowfin tuna | 47 mcg per 3 oz |
| Halibut | 45 mcg per 3 oz |
| Sardines | 18 mcg per 3 oz |
| Beef (ground) | 31 mcg per 3 oz |
| Turkey | 15 mcg per large egg |
Safety Information
Contraindications
- Do not exceed 400 mcg daily – selenosis (toxicity) can occur
- Skin cancer history - some studies suggest high selenium may increase squamous cell carcinoma risk
Potential Side Effects
- Garlic-like breath odor at high intakes (uncommon)
- Selenosis (>400 mcg): hair loss, nail brittleness, fatigue, irritability, neurological symptoms (rare)
- Selenosis (hair loss, nail brittleness, fatigue, irritability, neurological symptoms) at chronic high doses (uncommon)
Disclaimer: The information provided is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare provider before starting any supplement regimen.