Manganese vs Selenium (Selenomethionine)

Mechanism

Manganese is a cofactor for manganese superoxide dismutase (MnSOD/SOD2, the primary mitochondrial antioxidant enzyme), arginase (urea cycle), pyruvate carboxylase (gluconeogenesis), glutamine synthetase (ammonia detoxification in brain), and glycosyltransferases (proteoglycan/GAG synthesis for cartilage and bone). It activates several kinases and phosphatases involved in cell signaling. Manganese is essential for bone formation, cartilage integrity, and reproductive function.

Standard Dosing

2-5mg daily

Timing

With food. Often included in multimineral formulas.

Cycle Duration

ongoing (typically via multi-mineral or bone support formula)

Side Effects

• Generally well tolerated at standard doses
• Neurotoxicity at chronic high exposure (manganism — Parkinson-like syndrome)
• GI upset
• Headache

Contraindications

• Liver disease (Mn is hepatically cleared — accumulation risk)
• Iron deficiency (upregulated DMT1 increases Mn brain accumulation)
• Chronic occupational Mn exposure

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Mechanism

Selenium is incorporated as selenocysteine (the 21st amino acid) into 25 selenoproteins. Key enzymes: glutathione peroxidases (GPx1-4, reduce hydrogen peroxide and lipid hydroperoxides), thioredoxin reductases (TrxR1-3, maintain cellular redox balance), iodothyronine deiodinases (DIO1-3, convert T4 to T3 and regulate thyroid hormone metabolism), selenoprotein P (selenium transport and brain antioxidant), and selenoprotein W (muscle antioxidant). Selenium is essential for thyroid function, immune defense, reproductive health, and cancer chemoprevention.

Standard Dosing

200 mcg selenomethionine daily

Timing

With meals. Can be taken any time of day.

Cycle Duration

ongoing

Side Effects

• Garlic breath/body odor (selenosis)
• GI upset
• Hair loss and nail brittleness (toxicity)
• Fatigue
• Peripheral neuropathy (chronic excess)
• Potential type 2 diabetes risk at high doses (SELECT trial observation)

Contraindications

• Selenium excess (>400 mcg/day — narrow therapeutic window)
• Non-melanoma skin cancer history (SELECT trial concern)

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