Selenium

What It Is

Selenium is an essential trace mineral required by the human body in small amounts for various physiological functions. It is naturally found in foods such as Brazil nuts, seafood, eggs, whole grains, and organ meats. Selenium is also available as a dietary supplement, either alone or in combination with vitamins and other minerals.

In the body, selenium is a critical component of several enzymes and proteins known as selenoproteins, which play key roles in metabolism, DNA synthesis, reproduction, and protection against oxidative damage.

How It Works

Selenium exerts its effects primarily through its incorporation into selenoproteins, which have antioxidant and regulatory functions. The most notable of these include glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases.

1. Antioxidant Defense: Selenium-containing enzymes help neutralize free radicals and reactive oxygen species that can damage cells and tissues. This antioxidant effect helps reduce oxidative stress, which contributes to aging and various chronic diseases.
2. Thyroid Function: Selenium is necessary for the conversion of the thyroid hormone thyroxine (T4) into its active form triiodothyronine (T3). It supports thyroid gland function and protects it from oxidative damage.
3. Immune Support: Selenium enhances immune response by promoting the proliferation of immune cells and helping regulate inflammation. It also influences how the body responds to infections.
4. DNA Synthesis and Repair: Through its role in certain enzymes, selenium contributes to maintaining the integrity of genetic material and assists in repairing damaged DNA.

Why It’s Important

1. Protection Against Disease: Adequate selenium intake is linked to a lower risk of certain chronic conditions such as cardiovascular disease, some cancers, and cognitive decline. Its antioxidant role helps prevent cell damage associated with these diseases.
2. Immune System Health: Selenium supports the immune system’s ability to fight infections. Deficiency has been associated with increased susceptibility to viral infections and inflammatory disorders.
3. Thyroid Health: The thyroid gland contains more selenium per gram of tissue than any other organ in the body. Selenium deficiency can contribute to thyroid dysfunction, such as hypothyroidism or autoimmune thyroid diseases like Hashimoto’s thyroiditis.
4. Reproductive Health: Selenium plays a role in sperm motility and overall male fertility. In women, adequate selenium levels contribute to proper ovarian function and pregnancy outcomes.

Considerations

1. Deficiency Risks: Selenium deficiency can occur in areas where soil selenium content is low, leading to reduced levels in locally grown foods. Deficiency symptoms may include fatigue, muscle weakness, compromised immunity, and in severe cases, conditions such as Keshan disease (a heart disorder) or Kashin-Beck disease (a bone and joint disorder).
2. Toxicity and Overconsumption: While selenium is essential, too much can be harmful. Chronic overconsumption can cause selenosis, characterized by hair and nail brittleness, gastrointestinal disturbances, a garlic-like odor on the breath, and in severe cases, nervous system abnormalities. The upper safe intake limit for adults is around 400 micrograms per day.
3. Interactions: Selenium interacts with other nutrients, such as vitamin E, in enhancing antioxidant defenses. However, supplementation should be approached cautiously, especially for those already receiving adequate amounts from their diet.
4. Individual Variability: The need for selenium may vary depending on age, health status, and specific conditions (e.g., thyroid disorders, chronic infections, or inflammatory diseases). Consultation with a healthcare provider before supplementation is recommended.