What is Selenium?

Selenium is an essential trace element that, despite being present in small amounts in the body, plays an outstanding role in metabolism, cell protection, immune function, thyroid function, and fertility. It acts primarily as a component of important enzymes—so-called selenoproteins—which are responsible for antioxidant protection, detoxification, and hormone regulation.

Selenium was only recognized as an essential nutrient in the mid-20th century. Today, we know it is indispensable for protecting cells from oxidative stress, regulating the thyroid, and strengthening the immune system. Particularly interesting is that selenium levels in foods depend heavily on the soil—in Central Europe, soils are often low in selenium, which is why inadequate intake is relatively common.

Natural sources of selenium include Brazil nuts, fish, seafood, eggs, meat, whole grains, and mushrooms.

How does Selenium work?

Selenium exerts its effects mainly through selenoproteins, which are involved in a wide range of biological processes.

Cell protection and antioxidant effects:
Selenium is a component of the enzyme glutathione peroxidase, which neutralizes free radicals and protects cells from oxidative stress. This antioxidant effect plays a crucial role in preventing cell damage, aging processes, and inflammation.

Thyroid function:
Selenium is essential for converting the thyroid hormone thyroxine (T4) into its active form, triiodothyronine (T3). It also protects the thyroid from oxidative stress caused by hormone production. Adequate selenium intake is therefore essential for healthy metabolism, energy balance, and hormonal balance—especially in combination with iodine.

Immune system:
Selenium increases the activity of immune cells (e.g., lymphocytes and natural killer cells) and promotes antibody production. This can improve the body's defenses against viruses and bacteria and strengthen resistance to infections.

Cardiovascular system:
Through its antioxidant properties, selenium protects blood vessels from oxidative damage and thus helps maintain healthy heart function. Studies suggest that adequate selenium intake combined with vitamin E may reduce the risk of cardiovascular disease.

Fertility and reproduction:
Selenium supports the formation of healthy sperm and protects them from oxidative damage. In women, it plays a role in egg maturation and pregnancy.

Skin, hair, and nails:
Selenium helps maintain normal hair and nails, as it is involved in the formation of keratin and protects skin cells from oxidative stress.

Benefits of Selenium

  • Acts as a powerful antioxidant and protects cells from free radicals

  • Supports thyroid function and hormone production

  • Strengthens the immune system and the body's defenses

  • Promotes heart health and helps prevent vascular damage

  • Supports fertility and reproduction in men and women

  • Helps maintain healthy hair, skin, and nails

  • Works synergistically with vitamin E to protect cells

Possible Side Effects and Interactions

Selenium is essential in small amounts but can be toxic in excessive doses. The recommended daily amount for adults is approximately 55–70 µg. Taking more than 300–400 µg daily over a prolonged period can lead to selenosis—a form of poisoning that can cause hair loss, brittle nails, skin irritation, fatigue, garlic-smelling breath, or stomach problems.

People with thyroid disorders should take selenium supplements only in consultation with their doctor, especially if they are already using iodine or thyroid hormones.

The combination of selenium and vitamin E is considered particularly effective, as the two nutrients regenerate each other and provide antioxidant cell protection together.

Conclusion

Selenium is a small trace element with a big impact. It protects cells, strengthens the immune system, regulates the thyroid, and supports skin, hair, nails, and fertility. Adequate intake is essential for energy, vitality, and hormonal balance. Since many soils in Europe are low in selenium, targeted supplementation—especially in combination with vitamin E—may be beneficial for protecting the body and mind over the long term from oxidative stress and metabolic disorders.

Sources

  1. Rayman MP. (2012): Selenium and human health. Lancet, 379(9822), 1256–1268.

  2. Drutel A, Archambeaud F, Caron P. (2013): Selenium and the thyroid gland: more good news for clinicians. Clin Endocrinol (Oxf), 78(2), 155–164.

  3. Steinbrenner H, et al. (2015): Functions of selenoproteins and biomarkers of selenium status. Antioxid Redox Signal, 23(10), 814–828.

  4. Fairweather-Tait SJ, et al. (2011): Selenium in human health and disease. Antioxid Redox Signal, 14(7), 1337–1383.