Selenium is an essential trace mineral that plays a vital role in human health. Although the body only requires small amounts, selenium is involved in numerous biological processes that help maintain normal cellular function.
Selenium is a key component of several specialised proteins known as selenoproteins, which support antioxidant defence, immune function and thyroid hormone metabolism.
One of selenium's most important roles is its involvement in the enzyme glutathione peroxidase, a key part of the body's natural antioxidant system.
Why Is Selenium Important?
Selenium contributes to several important functions within the body, including:
🛡️ Supporting antioxidant defences
🦠 Supporting normal immune function
🦋 Supporting normal thyroid hormone metabolism
🧬 Helping protect cells from oxidative damage
⚡ Supporting normal cellular function and metabolism
❤️ Supporting antioxidant processes that help maintain normal cellular function
Although required in only small amounts, selenium plays a significant role in maintaining overall health and wellbeing.
Selenium and Antioxidant Defence
Every day, the body produces unstable molecules known as free radicals as a natural by-product of metabolism.
While free radicals are a normal part of human physiology, excessive levels may contribute to oxidative stress, which can damage cells and tissues over time.
Factors that may increase oxidative stress include:
🚬 Smoking
☀️ Excessive UV exposure
🍟 Poor dietary habits
😴 Inadequate sleep
🦠 Illness and inflammation
Selenium helps form the enzyme:
🛡️ Glutathione Peroxidase
This important antioxidant enzyme helps neutralise free radicals and supports the body's natural defence systems against oxidative damage.
Selenium and Thyroid Health
🦋 The thyroid gland contains one of the highest concentrations of selenium in the body.
Selenium-dependent enzymes help convert the thyroid hormone thyroxine (T4) into its active form, triiodothyronine (T3).
Adequate selenium intake supports normal thyroid hormone metabolism and healthy thyroid function.
Selenium and Long-Term Health
Low selenium status has been associated with an increased risk of certain chronic diseases, although cause-and-effect relationships are not always clear.
Researchers continue to investigate selenium's role in:
❤️ Long-term health and wellbeing
🧬 Cellular protection and cancer research
🦠 Immune system health
🧠 Healthy ageing
However, selenium is only one of many factors that influence long-term health outcomes, alongside genetics, lifestyle and overall dietary patterns.
Dietary Sources of Selenium
The selenium content of plant foods depends largely on the amount of selenium present in the soil where they are grown.
Good dietary sources include:
🥩 Meat
🐟 Fish and seafood
🥚 Eggs
🌰 Brazil nuts
Plant-based sources may also include:
🥦 Vegetables
🍎 Fruits
🌾 Wholegrains and cereals
However, selenium levels in plant foods can vary considerably depending on soil conditions.
Brazil Nuts
🌰 Brazil nuts are among the richest natural sources of selenium.
Just one or two Brazil nuts may provide a substantial proportion of an adult's daily selenium requirement.
Because selenium concentrations can vary significantly between nuts, regular consumption of large quantities is generally not recommended.
How Much Selenium Do We Need?
The UK Reference Nutrient Intake (RNI) is:
👨 Men: 75 micrograms (µg) per day
👩 Women: 60 micrograms (µg) per day
Most people can achieve these levels through a varied and balanced diet.
Can You Have Too Much Selenium?
Although selenium is essential for health, excessive intake can be harmful.
Long-term intakes significantly above recommended levels may increase the risk of selenosis (selenium toxicity).
Symptoms may include:
⚠️ Hair loss
⚠️ Brittle or abnormal nails
⚠️ Gastrointestinal upset
⚠️ Fatigue
⚠️ A metallic taste in the mouth
⚠️ Garlic-like breath odour
Excessive selenium intake is far more likely to occur through high-dose supplementation than from food alone.
Selenium is an essential trace mineral that contributes to antioxidant defence, immune function and normal thyroid hormone metabolism.
Through its role in several selenium-dependent enzymes, including glutathione peroxidase, selenium helps protect cells from oxidative damage and supports normal physiological function throughout the body.
A balanced diet containing foods such as fish, meat, eggs and Brazil nuts can help maintain healthy selenium levels and support overall wellbeing.
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Educational purposes only. This article is intended for general health education and should not be used to diagnose, treat or cure any medical condition. If you have concerns about your nutritional status, thyroid health or selenium intake, speak with your GP, registered dietitian or another qualified healthcare professional.