Iron Bisglycinate vs Selenium (Selenomethionine)

Mechanism

Iron is essential for hemoglobin (oxygen transport), myoglobin (muscle oxygen storage), cytochrome enzymes (electron transport chain — Complexes I, II, III, IV), cytochrome P450 enzymes (drug/hormone metabolism), catalase (H2O2 decomposition), ribonucleotide reductase (DNA synthesis), and aconitase (Krebs cycle). Iron bisglycinate (Ferrochel) uses amino acid chelation to bypass the normal DMT1/ferroportin pathway, instead being absorbed intact via PepT1 transporter. This mechanism avoids the GI side effects of ionic iron (free Fe2+ generates hydroxyl radicals via Fenton reaction in the gut lumen) and is not inhibited by phytates, tannins, or calcium.

Standard Dosing

25-36mg elemental iron (as bisglycinate) daily for deficiency correction

Timing

On empty stomach or with vitamin C for absorption. Alternate day dosing (every other day) may be superior due to hepcidin cycling. Separate from calcium, zinc, tea, coffee by 2+ hours.

Cycle Duration

Until ferritin >50 ng/mL, then reassess (typically 3-6 months). Not for ongoing supplementation unless chronic blood loss.

Side Effects

• GI distress (significantly less than ferrous sulfate)
• Constipation (less common with bisglycinate)
• Dark stools
• Nausea
• Iron overload if supplemented unnecessarily

Contraindications

• Hemochromatosis
• Iron overload conditions
• Thalassemia (without documented deficiency)
• Hemolytic anemias (unless also iron deficient)
• Chronic transfusion therapy

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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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