Learn all about Selenium
What is Selenium?
Strengthen antioxidant defenses & thyroid function with essential selenium. Supports DNA repair & immune surveillance. Protect your cells!
Benefits of Selenium
- Supports antioxidant defence systems by forming essential components of glutathione peroxidase and other selenium-containing enzymes (selenoenzymes) that protect cells from damage[ref]
- Essential for proper thyroid function by helping convert the main thyroid hormone (T4) into the more active form (T3) using special selenium-containing enzymes (deiodinases)[ref]
"Selenium exemplifies the delicate balance required in micronutrient nutrition - the margin between deficiency and toxicity is narrower than for many nutrients, emphasising the importance of informed supplementation. While overt deficiency is rare in developed countries, suboptimal status may be more common than appreciated, particularly in regions with low soil selenium. The research on selenium's role in thyroid autoimmunity is particularly compelling, with supplementation showing benefits in Hashimoto's thyroiditis. However, the anticancer effects observed in some studies haven't been consistently reproduced, highlighting the complexity of selenium's biological roles. For most individuals, a diet rich in varied whole foods typically provides adequate selenium, but targeted supplementation may benefit specific populations, particularly when soil conditions or dietary restrictions limit natural intake."
- Dr. Margaret Rayman, Professor of Nutritional Medicine at the University of Surrey and leading selenium researcher (source)
How to use Selenium
Dosage
Adult Reference Nutrient Intake (RNI) is 60-75mcg daily for men and 60mcg daily for women; therapeutic dosages typically range from 100-200mcg daily; should not exceed 400mcg daily from all sources
Timing
Most effectively absorbed when taken with food, particularly meals containing some fat; can be taken any time of day with consistent timing
Notes
Selenium exists in multiple forms in supplements, with selenomethionine and selenium-enriched yeast typically having higher absorption than inorganic forms like sodium selenite; vegetarians and those living in selenium-poor soil regions may benefit most from supplementation
Who should take Selenium?
- Individuals living in regions with low selenium soil content (parts of Europe, New Zealand, and northeastern China)
- Those with compromised thyroid function, particularly autoimmune thyroiditis/Hashimoto's
- People with higher levels of cell damage due to environmental factors or chronic conditions
- Older adults with problems absorbing nutrients or higher signs of inflammation
How does Selenium work?
Selenium functions primarily through becoming part of special proteins (selenoproteins). The human body utilises selenium in approximately 25 selenoproteins, many of which help chemical reactions. The most well-characterised are the glutathione peroxidases, which neutralise harmful substances... preventing cell damage from harmful molecules (reactive oxygen species). Other selenium enzymes (Thioredoxin reductases) help keep cells balanced and control many body processes. In thyroid function, selenium is essential for enzymes (iodothyronine deiodinases) that activate or inactivate thyroid hormones... Another protein (Selenoprotein P) carries selenium in the blood and acts as an antioxidant on cell surfaces. Through these diverse selenoproteins, selenium influences inflammatory processes, making DNA, fertility, and protection against heavy metal toxicity, particularly mercury. The molecular form of selenium affects its absorption, bioavailability, and incorporation into these functional proteins.
Frequently asked questions
Natural sources of Selenium
Selenium content in foods varies dramatically based on the selenium concentration in the soil where plants are grown or where animals graze. Brazil nuts stand out as the richest dietary source, with a single nut potentially providing 68-91mcg, though content varies widely. Seafood, particularly yellowfin tuna, halibut, sardines, and oysters, offer consistent amounts ranging from 40-60mcg per 85g serving. Organ meats like kidney and liver contain significant selenium, reflecting animals' tendency to store the mineral. Among common proteins, turkey, chicken, beef, and lamb provide moderate amounts. Plant sources include whole grains (particularly those grown in selenium-rich soils), sunflower seeds, mushrooms (especially crimini and shiitake), and some legumes. In the UK, where soils are generally lower in selenium, imported foods from selenium-rich regions like North America contribute significantly to intake. Processing and cooking minimally affect selenium content, though boiling may leach some into cooking water.
Potential side effects & risks
Warnings
Not recommended in high doses during pregnancy without medical supervision; individuals with certain rare genetic conditions affecting making selenium proteins should exercise caution; diabetics should consult healthcare providers as selenium may influence glucose metabolism; those with existing thyroid conditions should coordinate supplementation with other treatments
Side effects
At doses within recommended ranges, side effects are rare; exceeding 400mcg daily may lead to selenosis (selenium toxicity) symptoms including hair loss, brittle nails, garlic breath odour, digestive distress, and skin rashes; very high doses can cause more serious neurological symptoms
Interactions
May increase bleeding risk when combined with anticoagulants; can potentially reduce efficacy of statin medications; may interact with certain chemotherapy drugs; can interfere with absorption of some antibiotics if taken simultaneously