Selenium (Se) is a chemical element that plays a significant role in various biological processes. It is recognized as a trace element, meaning the body requires it in very small quantities to function properly. Its influence extends across multiple bodily systems. Understanding its nature and biological impact offers insights into maintaining overall health.
What is Selenium?
Selenium is a chemical element identified by the symbol Se. It is classified as a non-metal and exists as a solid at room temperature. This element is found throughout the Earth’s crust, soil, and water, though its concentration can vary by geographic region. Selenium can exist in different forms, including inorganic compounds like selenates and selenites, and organic forms like selenomethionine and selenocysteine. These different forms influence how the body absorbs and utilizes the element.
How Selenium Works in Your Body
Selenium functions by being incorporated into selenoproteins, which are responsible for most of its biological actions. Selenoproteins, such as glutathione peroxidases (GPx) and thioredoxin reductases (TrxR), act as antioxidants. They help protect cells from damage caused by free radicals, which are unstable molecules that can lead to oxidative stress and contribute to various chronic conditions.
Selenoproteins also have an important role in the metabolism of thyroid hormones. The thyroid gland, which has a high concentration of selenium, relies on selenoproteins to convert inactive thyroid hormone (T4) into its active form (T3), influencing metabolism, growth, and development. Selenium also contributes to a healthy immune system. It supports the function and activation of immune cells, helping the body defend against infections and regulate inflammatory responses.
Where to Find Selenium
Selenium is widely distributed in the diet. Its content in plant-based foods often reflects the selenium levels in the soil, while animal products tend to have more consistent levels. Dietary sources include Brazil nuts, which are rich in the element, along with seafood such as tuna, halibut, and sardines.
Other sources are organ meats like beef liver, lean meats such as pork and chicken, and grains like brown rice and whole wheat pasta. Dairy products and eggs also contribute to selenium intake. While supplements are available, obtaining selenium through a balanced diet is generally recommended.
Getting the Right Amount
Maintaining the correct balance of selenium intake is important due to its narrow therapeutic window; both insufficient and excessive amounts can lead to health issues. A deficiency can impair immune function, making the body more susceptible to illness. It can also affect thyroid function and, in severe cases, contribute to heart conditions or muscle weakness. Symptoms of low selenium might include fatigue, hair loss, and mental fog.
Conversely, consuming too much selenium can result in selenosis. Symptoms of toxicity include a garlic-like odor on the breath, a metallic taste in the mouth, and gastrointestinal disturbances like nausea and diarrhea. Severe signs include hair loss, brittle or discolored nails, skin rashes, and fatigue. For these reasons, it is advisable to obtain selenium from a varied diet and to consult a healthcare professional before taking supplements.