10/31/2025
Vitamin B12 acts as a cofactor (helper molecule) for several essential enzymes.
Without it, major cellular reactions slow down or malfunction — especially those involving DNA synthesis, methylation, and energy metabolism.
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🧬 1. DNA Synthesis & Cell Division
• B12 is required for thymidine synthesis, a building block of DNA.
• Works alongside folate (vitamin B9) — they are tightly linked.
• When B12 is low, folate becomes “trapped” in an unusable form (the methyl trap), leading to impaired DNA replication.
👉 Affects rapidly dividing cells most — like red blood cells, gut lining, skin, and hair.
Result of deficiency: megaloblastic anemia, fatigue, poor wound healing.
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⚡️ 2. Energy Production (Mitochondrial Function)
B12 is required for fat and amino acid metabolism, converting nutrients into usable energy.
Key enzyme:
Methylmalonyl-CoA mutase
• Converts methylmalonyl-CoA → succinyl-CoA (an important Krebs cycle intermediate).
• Without B12, methylmalonic acid (MMA) builds up and mitochondria can’t efficiently produce ATP.
👉 Result of deficiency: fatigue, weakness, exercise intolerance, and sometimes myelin damage.
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🧠 3. Methylation Cycle & Neurotransmitter Production
B12 (as methylcobalamin) is a cofactor for:
Methionine synthase, which converts:
Homocysteine → Methionine → S-adenosylmethionine (SAMe)
SAMe is the body’s universal methyl donor used in:
• Neurotransmitter synthesis (dopamine, serotonin, norepinephrine)
• Detoxification (phase II methylation)
• DNA methylation (epigenetic regulation)
• Hormone balance and liver metabolism
👉 Result of deficiency: depression, anxiety, cognitive decline, poor detox, and elevated homocysteine.
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🧠 4. Myelin Synthesis and Nerve Function
• B12 is essential for myelin sheath formation (protective coating around nerves).
• Helps convert methylmalonyl-CoA to succinyl-CoA, a step in producing myelin lipids.
👉 Result of deficiency: tingling, numbness, neuropathy, balance problems, memory issues.
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❤️ 5. Homocysteine Regulation & Cardiovascular Health
• B12, folate, and B6 help metabolize homocysteine (a pro-inflammatory amino acid).
• Without enough B12, homocysteine rises, damaging blood vessels and increasing cardiovascular risk.
👉 Result of deficiency: elevated homocysteine, inflammation, and vascular damage.
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🧫 6. Red Blood Cell Formation
• B12 is critical in the bone marrow for maturation of red blood cells.
• Without it, RBCs become large and fragile (megaloblasts).
👉 Result: anemia, low oxygen delivery, fatigue, shortness of breath.
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🌿 7. Detoxification & Liver Function
• Through methylation and SAMe, B12 supports phase II liver detox pathways.
• Important for estrogen metabolism, histamine clearance, and glutathione synthesis.
👉 Result of deficiency: sluggish detox, hormonal imbalance, histamine intolerance.