🧬 Family & Essentiality

🌿 Plain-Language Summary

Vitamin B6 is needed by more than 100 enzymes, mainly in amino acid metabolism. Its active form, PLP, helps make neurotransmitters like serotonin, dopamine, and GABA, supports haemoglobin production, and assists in keeping homocysteine levels balanced for heart health.

⚗️ Molecular & Chemical IDs

• Pyridoxine: C₈H₁₁NO₃ (CAS 65-23-6)
• PLP: C₈H₁₀NO₆P
• Note: Plant foods often contain pyridoxine-glucosides, which have lower bioavailability

⚡ Functions

• Amino-transfer reactions in protein and amino acid metabolism
• Neurotransmitter synthesis: serotonin, dopamine, GABA
• Haem synthesis → supports red blood cell formation
• Homocysteine → cysteine (with folate & B12)
• Tryptophan → niacin conversion (with B2 support)

🍽️ Absorption & Bioavailability

🇦🇺 Australian NRVs (NHMRC)

• Adult men: 1.3–1.7 mg/day
• Adult women: 1.3–1.5 mg/day
• Pregnancy: 1.9 mg/day
• Lactation: 2.0 mg/day

UL (adults): 50 mg/day (pyridoxine)

🚨 Deficiency & Excess

Deficiency

• Microcytic anaemia (due to impaired haem synthesis)
• Peripheral neuropathy
• Seborrhoeic dermatitis (scaly red rash)
• Cheilitis, glossitis, irritability, fatigue

Toxicity Alert

Chronic high-dose B6 (>100 mg/day) can cause sensory axonopathy (nerve fibre damage, “stocking-glove” neuropathy), often irreversible.

🥗 Food Sources

• Poultry, fish, beef, liver
• Potato, banana, chickpeas, whole grains
• Cultural note: potatoes and bananas are major contributors in many diets

🧪 Testing & Monitoring

• Serum PLP <30 nmol/L suggests deficiency
• Erythrocyte transaminase activity better reflects longer-term status

🔗 Interactions

• Isoniazid, hydralazine, oral contraceptives may deplete B6
• Alcohol misuse increases requirements

📊 Evidence Snapshot

• 🔬✅ Well-established: Essential in amino acid metabolism, haem synthesis, neurotransmitters
• 🧪⚖️ Clinical: Used under supervision for deficiency states and selected conditions
• ⚠️❌ Unproven/hype: High-dose use in healthy individuals lacks supporting evidence