Selenium

Selenium is a crucial nutrient for the conversion of T4 to T3, a process necessary for proper thyroid function. Ray Peat argued that selenium is the most crucial nutrient for this conversion, and that the brain, kidneys, and skin have the equipment to convert T4 to T3, but need selenium to do so 2.

Selenium also plays a role in the production of energy, as it is necessary for the functioning of the mitochondrial enzyme cytochrome c oxidase, which is the last step in the production of oxidative energy 1. Additionally, selenium has been shown to have antioxidant properties, activating the thyroid and preventing random, harmful oxidative damage 6.

Adequate selenium levels have been linked to improved thyroid function, and deficiencies in selenium have been associated with a range of health problems, including fatigue, low progesterone, and low testosterone 1. Foods rich in selenium include seafood, such as oysters and shrimp, as well as mushrooms 2.

Exercise has been shown to increase brain selenium levels, which may contribute to its brain-boosting effects 4. However, high doses of selenium can be toxic, and the optimal dosage for humans is still a matter of debate 4.

In contrast to estrogen, which can produce reductive stress to the cell, selenium works with the thyroid to keep the cell in its resting, oxidized state 6. Progesterone also opposes the effects of estrogen, working with the thyroid to maintain a healthy balance 6.

Overall, selenium is a critical nutrient for thyroid function, energy production, and overall health, and deficiencies in selenium can have serious consequences 2.