Potassium (Citrate) vs Selenium (Selenomethionine)

Mechanism

Potassium is the principal intracellular cation, maintaining resting membrane potential (-70 to -90mV) via the Na+/K+-ATPase pump (3 Na+ out, 2 K+ in per ATP). It is essential for: cardiac rhythmicity (phase 3 repolarization of cardiac action potential), skeletal muscle contraction, nerve impulse transmission, acid-base balance (exchanged for H+ in renal tubules), blood pressure regulation (promotes natriuresis via renal sodium excretion), and insulin secretion. Citrate form provides alkalinizing anion that inhibits calcium oxalate and uric acid kidney stone formation.

Standard Dosing

99-200mg per capsule (regulatory limit in US); dietary target 3500-4700mg/day total

Timing

With meals, divided throughout the day. Slow-release forms preferred for higher doses.

Cycle Duration

ongoing

Side Effects

• GI irritation/ulceration (non-microencapsulated forms)
• Nausea
• Diarrhea
• Hyperkalemia (dangerous — cardiac arrhythmias)

Contraindications

• Hyperkalemia
• Renal insufficiency (impaired K+ excretion)
• Addison's disease (aldosterone deficiency)
• Concurrent ACE inhibitor/ARB + potassium-sparing diuretic

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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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