Selenium

Selenium

Selenium is a trace element that is essential for human health. It is a component of several major metabolic pathways, including thyroid hormone metabolism, antioxidant defense systems, and immune function. Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes.

Biological Role

Selenium plays a critical role in the body by contributing to the antioxidant defense system, which protects cells from damage caused by free radicals. It is also essential for the proper functioning of the thyroid gland, as it is involved in the conversion of thyroxine (T4) to triiodothyronine (T3), the active form of thyroid hormone.

Antioxidant Function

Selenium is a key component of the enzyme glutathione peroxidase, which helps to reduce oxidative stress by neutralizing harmful peroxides. This function is crucial in protecting cells from oxidative damage, which can lead to chronic diseases such as cancer and cardiovascular disease.

Thyroid Function

The thyroid gland contains more selenium per gram of tissue than any other organ in the body. Selenium-dependent enzymes, such as iodothyronine deiodinases, are responsible for the activation and deactivation of thyroid hormones. Adequate selenium levels are necessary to maintain optimal thyroid function and metabolism.

Immune System

Selenium is important for the immune system, as it enhances the proliferation of activated T-cells and the production of antibodies. It also plays a role in the regulation of inflammation and the prevention of infections.

Dietary Sources

Selenium is found in a variety of foods. The amount of selenium in plant-based foods depends on the selenium content of the soil in which they are grown. Animal-based foods generally have more consistent selenium levels.

Rich Sources

- Brazil nuts - Seafood (e.g., tuna, halibut, sardines) - Meat (e.g., beef, chicken, turkey) - Eggs - Dairy products

Deficiency

Selenium deficiency can lead to several health problems, including Keshan disease, a type of cardiomyopathy, and Kashin-Beck disease, a type of osteoarthropathy. Symptoms of selenium deficiency may include muscle weakness, fatigue, and mental fog.

Toxicity

While selenium is essential for health, excessive intake can lead to selenium toxicity, known as selenosis. Symptoms of selenosis include gastrointestinal disturbances, hair loss, white blotchy nails, and mild nerve damage.

Recommended Intake

The recommended dietary allowance (RDA) for selenium varies by age, sex, and life stage. For adults, the RDA is 55 micrograms per day. Pregnant and lactating women have higher requirements.

See Also

• Trace elements
• Antioxidants
• Thyroid hormone
• Immune system

Trace Elements in Tissues and Biologic Systems

Aluminum	Copper	Nickel
Antimony	Fluorine	Rubidium
Barium	Iodine	Selenium
Boron	Lead	Silver
Bromine	Lithium	Strontium
Cadmium	Manganese	Tin
Chromium	Mercury	Vanadium
Cobalt	Molybdenum	Zinc

Nutrition information of Selenium

• USDA on Selenium