What is selenium?
Selenium is an essential trace element that, despite its low levels in the body, is of great importance for metabolism, cell protection, the immune system, thyroid function, and fertility. It primarily acts as a component of important enzymes - known as 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 that it is indispensable for protecting cells from oxidative stress, regulating the thyroid, and strengthening the immune system. It is particularly interesting that selenium levels in foods depend heavily on the soil - in Central Europe, these soils are often low in selenium, which is why insufficient intake is relatively common.
Natural sources of selenium include Brazil nuts, fish, seafood, eggs, meat, whole-grain products, and mushrooms.
How does selenium work?
Selenium exerts its effects primarily through selenoproteins, which are involved in a wide range of biological processes.
Cell protection and antioxidant activity:
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 the active form triiodothyronine (T3). It also protects the thyroid from oxidative stress caused by hormone production. An adequate selenium supply is therefore crucial for a healthy metabolism, energy balance, and hormonal equilibrium - especially in combination with iodine.
Immune system:
Selenium increases the activity of immune cells, such as lymphocytes and natural killer cells, and promotes antibody production. This can improve the body's defense against viruses and bacteria and strengthen resistance to infections.
Cardiovascular system:
Through its antioxidant properties, selenium protects blood vessels from oxidative damage and thereby contributes to maintaining healthy heart function. Studies suggest that adequate selenium intake in combination 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 contributes to maintaining normal hair and nails, as it is involved in keratin formation and protects skin cells from oxidative stress.
Benefits of selenium
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Acts as a powerful antioxidant and protects cells from free radicals
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Supports thyroid function and hormone production
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Strengthens the immune system and the body's defenses
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Promotes heart health and prevents vascular damage
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Supports fertility and reproduction in men and women
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Contributes to maintaining healthy hair, skin, and nails
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Works synergistically with vitamin E to protect cells
Possible side effects and interactions
Selenium is essential for life in small amounts, but can be toxic in excessive doses. The recommended daily amount is approximately 55–70 µg for adults. Intake of more than 300–400 µg per day over a prolonged period can lead to selenosis - poisoning that may manifest as hair loss, brittle nails, skin irritation, fatigue, garlic odor of the breath, or stomach problems.
People with thyroid disorders should only take selenium supplements in consultation with a doctor, especially if they already use iodine or thyroid hormones.
The combination of selenium and vitamin E is considered particularly effective, as both nutrients regenerate one another and provide antioxidant cell protection together.
Conclusion
Selenium is a small trace element with major effects. It protects cells, strengthens the body's defenses, regulates the thyroid, and supports the skin, hair, nails, and fertility. Adequate intake is crucial for energy, vitality, and hormonal balance. Since many soils in Europe are low in selenium, targeted supplementation - particularly in combination with vitamin E - may be beneficial for protecting the body and mind from oxidative stress and metabolic disorders in the long term.
Sources
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Rayman MP. (2012): Selenium and human health. Lancet, 379(9822), 1256–1268.
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Drutel A, Archambeaud F, Caron P. (2013): Selenium and the thyroid gland: more good news for clinicians. Clin Endocrinol (Oxf), 78(2), 155–164.
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Steinbrenner H, et al. (2015): Functions of selenoproteins and biomarkers of selenium status. Antioxid Redox Signal, 23(10), 814–828.
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Fairweather-Tait SJ, et al. (2011): Selenium in human health and disease. Antioxid Redox Signal, 14(7), 1337–1383.
