12. Selenium

Selenium is needed for creation of many enzymes that act as antioxidants, reducing free radical damage to your cells. It is necessary for creation of selenoproteins, which turn thyroid hormones on and off, and protect the thyroid from damage during creation of these hormones. It also plays a key role in creation of T cells, a type of white blood cell that helps prevent infections. Sources include meats, poultry, nuts, seeds, and grains.

Quick Facts
-Needed for creation of many enzymes that act as antioxidants, reducing free radical damage to your cells
-Necessary for creation of selenoproteins, which turn thyroid hormones on and off, and protect the thyroid from damage during creation of these hormones
-Key role in creation of T cells, a type of white blood cell that helps prevent infections
[79]

RDI
Males 19 – 30 yrs: 55 μg
Females 19 – 30 yrs: 55 μg
[128]

Deficiency
-Symptoms include infertility, muscle weakness, fatigue, mental fog, hair loss, and a weakened immune system [200]

Toxicity
-Upper limit is recommended as 400 μg / day [201]
-In a study where 201 people accidentally took a median dose of 41,749 μg / day. Symptoms included diarrhea (78%), fatigue (75%), hair loss (72%), joint pain (70%), nail discoloration or brittleness (61%), and nausea (58%). Some symptoms persisted for 90 days or longer [202].

Sources
Meats, poultry, nuts, seeds, grains
[79]