Selenium is a trace mineral the body needs only in tiny amounts, yet its influence is far-reaching. It forms the active core of selenoproteins — specialised enzymes that defend cells from oxidative damage and govern how the thyroid works. Brazil nuts are famously rich in it, so much so that a couple a day can meet daily needs, while fish, eggs, poultry and wholegrains contribute steadily. Soil content varies widely between regions, so dietary intake can too. Both too little and too much carry risks, making selenium a nutrient best kept within a sensible range.
What is Selenium?
Selenium is a trace mineral that plays a critical role in antioxidant defence, thyroid hormone metabolism, and protecting cells from oxidative stress. While many general diets overlook it, maintaining optimal levels of Selenium is frequently tracked by people working to optimize their Antioxidant & thyroid status.
Top Foods High in Selenium
A data-driven breakdown of the foods with the highest concentration of Selenium per 100 g.
| Food | Selenium | % DV |
|---|---|---|
| Flaxseed | 135.9 µg | 247.1% |
| Tuna (canned, light) | 70.6 µg | 128.4% |
| Sardines | 52.7 µg | 95.8% |
| Mussels | 44.8 µg | 81.5% |
| Mackerel | 44.1 µg | 80.2% |
| Sesame Seeds | 34.4 µg | 62.5% |
| Wholewheat Pasta | 34.2 µg | 62.2% |
| Cod | 33.1 µg | 60.2% |
| Eggs | 30.7 µg | 55.8% |
| Oats | 28.9 µg | 52.5% |
| Cheddar Cheese | 28.3 µg | 51.5% |
| Couscous | 27.5 µg | 50% |
| Rainbow Trout | 23.6 µg | 42.9% |
| Pistachios | 23.12 µg | 42% |
| Millet | 23.1 µg | 42% |
How Selenium Impacts Antioxidant & thyroid status
Research links diets rich in Selenium to changes in Antioxidant & thyroid status. Optimizing intake of these foods can support healthy Antioxidant & thyroid status levels via serving as the catalytic core of glutathione peroxidase, which neutralises harmful peroxides, and of the deiodinase enzymes that convert thyroid hormone into its active form.
Written by the Nutrition Encyclopedia team · medically reviewed by Dr. Sunaina Tariq, MBBS
Last updated 22 June 2026
How we source & verify data · Medical disclaimer
Nutrition values are approximations compiled from public food-composition databases (USDA FoodData Central) and are provided for educational purposes only — not medical advice.
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