Selenium
With meals
Selenium is an essential trace mineral found naturally in Brazil nuts, seafood, and organ meats. It serves as a critical cofactor for selenoproteins, a family of enzymes involved in antioxidant defense, thyroid hormone regulation, and immune signaling. While most people obtain adequate selenium through diet, soil depletion in certain regions can lead to suboptimal intake.
Research Evidence
Reduces oxidative stress via glutathione peroxidase activity
StrongPotential mood and cognitive benefits in deficient individuals
LimitedSupports innate and adaptive immune responses
ModerateMay reduce prostate cancer risk in selenium-deficient populations
LimitedMay lower thyroid antibody levels in Hashimoto's thyroiditis
ModerateSupports thyroid hormone conversion (T4 to T3)
StrongExpert Evidence
8 references from 3 experts
“One of the best ways to support the thyroid system and metabolism in general is to make sure you're getting enough selenium. Brazil nuts, one or two or three of those per day, you'll have more than enough selenium.”
How to Lose Fat with Science-Based Tools
17:475 references in 3 episodes from 2021–2025
2025
2024
2021
2014
Safety & Cautions
Side Effects
- Garlic-like breath odor at high doses
- Nausea or GI discomfort
- Hair and nail brittleness with chronic excess
- Selenosis (toxicity) from prolonged intake above 400 mcg/day
Selenium has a relatively narrow therapeutic window compared to other minerals, so staying within recommended doses is important. It is generally well-tolerated at 100–200 mcg/day, but long-term megadosing can lead to toxicity symptoms including fatigue, irritability, and peripheral neuropathy.
Pairs Well With