Boron vs Selenium (Selenomethionine)

Mechanism

Boron influences calcium, magnesium, and phosphorus metabolism, likely through effects on cell membrane function and transmembrane signaling. It reduces urinary calcium and magnesium excretion, increases serum 25(OH)D and estradiol levels, reduces SHBG (sex hormone-binding globulin) thereby increasing free testosterone, and inhibits inflammatory markers (CRP, TNF-alpha) via NF-kB modulation. Boron also inhibits serine proteases and may modulate the activity of steroid hormone hydroxylases. It plays a role in bone formation by influencing osteoblast and osteoclast activity.

Standard Dosing

3-6mg daily

Timing

With meals. Often taken with Vitamin D/K stack.

Cycle Duration

ongoing

Side Effects

• Nausea at high doses
• Diarrhea
• Skin rash (rare)
• Generally very well tolerated at standard doses

Contraindications

• Estrogen-sensitive cancers (boron increases estradiol)
• Renal impairment (boron is renally excreted)

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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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