🧬 Family & Essentiality

🌿 Plain-Language Summary

Vitamin B7 (biotin) is a coenzyme that helps your body process fats, carbohydrates, and proteins. It acts in critical carboxylase enzymes that support energy production, fatty acid synthesis, and amino acid breakdown. Deficiency is uncommon but can be serious in specific situations, such as inherited biotinidase deficiency, high raw egg white consumption, or long-term anticonvulsant use.

⚗️ Molecular & Chemical IDs

• Biotin: C₁₀H₁₆N₂O₃S (CAS 58-85-5)
• Properties: Heat-stable; avidin in raw egg white binds biotin and prevents absorption

⚡ Functions

• Coenzyme for acetyl-CoA carboxylase → fatty acid synthesis
• Coenzyme for pyruvate carboxylase → gluconeogenesis
• Coenzyme for propionyl-CoA carboxylase → odd-chain fatty acid & amino acid metabolism
• Supports normal cell growth, energy balance, and metabolic flexibility

🍽️ Absorption & Bioavailability

Gut microbiota also contribute small amounts of biotin.

🇦🇺 Australian NRVs (NHMRC — Adequate Intake)

• Adults: 30 µg/day
• Pregnancy: 30 µg/day
• Lactation: 35 µg/day

UL (Upper Level): Not established

🚨 Deficiency & Excess

Deficiency

• Hair loss, brittle nails, and periorificial skin rash (around eyes, nose, mouth)
• Conjunctivitis, lethargy, irritability
• Infants: low muscle tone (“floppy infant”), developmental delay if severe
• Newborn screening (AU): Biotinidase deficiency (~1:60,000) is screened at 48–72h after birth; early treatment prevents disability

Excess

No known toxicity from food. High-dose supplements (often marketed for hair/nails) can interfere with lab tests if taken in large amounts.

🥗 Food Sources

• Eggs (cooked), liver (occasional; avoid excess in pregnancy due to vitamin A)
• Nuts, seeds, legumes, whole grains
• Some vegetables, mushrooms

🧪 Testing & Monitoring

• Serum biotin reflects recent intake; urinary biotin/metabolites may provide additional info
• Lab interference: Biotin >5–10 mg/day can skew sandwich immunoassays (TSH, troponin, hormones). Pause supplements ≥72h before testing (confirm with lab)

🔗 Interactions

• Anticonvulsants can reduce biotin status
• Alcohol misuse and malabsorption ↑ deficiency risk

📊 Evidence Snapshot

• 🔬✅ Well-established: Coenzyme roles in carboxylase-dependent metabolism
• 🧪⚖️ Clinical: Supplementation for deficiency, pregnancy/lactation adequacy, biotinidase deficiency
• ⚠️❌ Unproven/hype: High-dose hair/nail claims in otherwise well-nourished individuals