Selenium: Essential Trace Mineral and Antioxidant

What is Selenium?

Selenium is an essential trace mineral that functions as a powerful antioxidant in the human body. It belongs to the class of micronutrients required in small amounts for optimal health and is commonly available as a dietary supplement. Selenium is primarily used to support immune function, thyroid health, and protect cells from oxidative damage caused by free radicals.

Uses

• Thyroid function support: Selenium is essential for the production and metabolism of thyroid hormones, particularly the conversion of T4 to the active T3 hormone.
• Immune system enhancement: Helps maintain proper immune response and may reduce the risk of infections, particularly in selenium-deficient populations.
• Antioxidant protection: Acts as a cofactor for glutathione peroxidase enzymes that protect cells from oxidative stress and DNA damage.
• Cardiovascular health: May help reduce inflammation and support heart health through its antioxidant properties.
• Cancer risk reduction: Some studies suggest selenium supplementation may help reduce the risk of certain cancers, though evidence remains mixed.

How it works

Selenium functions primarily as a component of selenoproteins, which are enzymes that have antioxidant properties. The most important of these is glutathione peroxidase, which protects cell membranes from damage by neutralizing harmful free radicals. Selenium also plays a crucial role in thyroid hormone metabolism by supporting the enzymes that convert inactive thyroid hormone (T4) to its active form (T3).

Side effects

Common side effects (with appropriate doses):

• Garlic-like breath odor
• Metallic taste in mouth
• Mild nausea
• Hair changes or brittleness
• Nail changes or brittleness
• Fatigue
• Skin rash

Serious side effects (selenium toxicity):

Submit Your Paper

• Hair loss (alopecia)
• Severe gastrointestinal upset and diarrhea
• Neurological symptoms including peripheral neuropathy
• Respiratory distress
• Heart problems or cardiac dysfunction

Warnings and precautions

• Pregnancy and breastfeeding: Generally considered safe in recommended doses, but excessive intake should be avoided as it may harm the developing fetus.
• Kidney disease: Patients with kidney problems should consult their healthcare provider before supplementation as selenium elimination may be impaired.
• Autoimmune thyroid conditions: People with autoimmune thyroid diseases should use caution and medical supervision when taking selenium supplements.
• Narrow therapeutic window: The difference between beneficial and toxic doses is relatively small, making proper dosing critical.
• Surgery: May increase bleeding risk when combined with certain medications, so supplementation should be discontinued before scheduled surgeries.

Interactions

• Warfarin and anticoagulants: May enhance anticoagulant effects, increasing bleeding risk
• Cisplatin and chemotherapy drugs: May reduce the effectiveness of certain cancer treatments
• Statins: High-dose selenium may reduce the effectiveness of cholesterol-lowering medications
• Vitamin C: Large doses of vitamin C may reduce selenium absorption
• Zinc supplements: High zinc intake may interfere with selenium absorption
• Niacin (Vitamin B3): May reduce selenium levels in the body
• Birth control pills: May decrease selenium levels, potentially requiring dosage adjustment
• Antacids: May reduce selenium absorption when taken simultaneously

Check interactions with the GMJ Interaction Checker

Evidence summary

The scientific evidence for selenium supplementation varies by indication. There is strong evidence supporting its role in thyroid function and immune system support, particularly in selenium-deficient populations. Moderate evidence exists for its antioxidant benefits and potential cardiovascular protection. However, there is limited evidence for cancer prevention, with some studies showing benefits while others show no effect or potential harm. The evidence for cognitive protection and fertility enhancement remains insufficient for definitive recommendations. For comprehensive safety information and detailed research summaries, visit supplement.ge.

Dosage

The typical adult dosage ranges from 55-200 micrograms daily, with 55 micrograms being the recommended dietary allowance for most adults. Therapeutic doses may range up to 400 micrograms daily under medical supervision, though the upper safe limit is generally considered to be 400 micrograms per day for adults. Dosages should always be determined by a healthcare provider based on individual needs, selenium status, and health conditions, as the margin between therapeutic and toxic doses is relatively narrow.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

This work is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You are free to share and adapt this content with attribution to GMJ News (news.gmj.ge).