Selenium is the "star" trace element for combating free radicals. It is often found in food supplements for antioxidant action, combined with vitamins C and E.
Therefore, selenium is mainly known for its antioxidant role (it helps protect cells against oxidative stress), but its action doesn't stop there: it is involved in normal immune system function and helps thyroid function.
This trace element, stored in the liver and kidneys, is essential for healthy body function. Selenium is not produced by the body, so it must be provided in the daily diet.

Roles

Here are some of the main roles of selenium :

Protective role against oxidative stress (antioxidant).
It helps the immune system and therefore helps the body's defences against infection.
It helps maintain nails and hair and is also involved in hormone metabolism.

Daily requirements

Daily requirements in RNI (Reference Nutrient Intakes) for selenium are around 20 to 80 micrograms depending on the person (based on age and activity).

RNI (Reference Nutrient Intakes) table for selenium :

Age / Condition	RNI for Selenium
Children aged 1 to 3 years old	20 µg
Children aged 4 to 12 years old	30 à 45 µg
Adolescents 13 to 19 years old	50 µg
Men	60 µg
Women	50 µg
Pregnant women (> 3rd trimester)	60 µg
Breast-feeding women	60 µg
Elderly people	60 à 80 µg