What is Selenium?
Selenium is an essential trace mineral that the body needs in small amounts to function properly. It is found naturally in soil and enters the food chain through plants and animals. Selenium plays a critical role in antioxidant defence, thyroid hormone metabolism, immune function, and DNA synthesis.
Health Benefits
- Antioxidant protection — selenium is a component of glutathione peroxidase, one of the body's most powerful antioxidant enzymes
- Thyroid health — essential for thyroid hormone production and metabolism; deficiency can contribute to thyroid problems
- Immune function — supports the immune response and may help protect against certain infections
- Anti-inflammatory — some research suggests selenium may help reduce inflammation in conditions like rheumatoid arthritis
- Cancer prevention — population studies suggest adequate selenium levels may lower cancer risk
- Reproductive health — important for male fertility
Dietary Sources
- Brazil nuts — the richest source (just 1–2 per day provides the daily requirement)
- Fish and shellfish (tuna, sardines, oysters)
- Meat and poultry
- Eggs
- Dairy products
- Wholegrains (selenium content depends on soil levels)
Deficiency and Toxicity
Selenium deficiency is rare in the UK but can occur in people with malabsorption conditions. Symptoms include fatigue, hair loss, and weakened immunity. Too much selenium (selenium toxicity or selenosis) from high-dose supplements can cause nausea, hair loss, nail brittleness, and neurological problems. Do not exceed the recommended daily intake from supplements (400 micrograms/day for adults).