🔑 Core Function

• Collagen synthesis: Every third amino acid in collagen is glycine → vital for skin, bone, cartilage, and connective tissue.
• Neurotransmission: Acts as an inhibitory neurotransmitter in the spinal cord and brainstem.
• Detoxification: Conjugates toxins, bile acids, and certain drugs for excretion.
• Metabolic role: Precursor for creatine, haem, purines, and glutathione.

🧬 Family & Essentiality

🌿 Plain-Language Summary

Glycine is the body’s “tiny giant ⚪”. Although the smallest amino acid, it is indispensable for collagen (skin, joints, bones), calming neurotransmission, and detoxification. It also helps make DNA, haemoglobin, creatine, and glutathione.

⚗️ Molecular & Chemical IDs

• Abbreviation: Gly / G
• Chemical formula: C₂H₅NO₂
• Structure: Simplest amino acid; side chain is a single hydrogen atom

⚡ Functions

• Structural: Backbone of collagen and elastin.
• Neurotransmitter: Inhibitory signalling; modulates NMDA receptors.
• Detoxification: Conjugates bile acids, benzoate, and certain drugs.
• Biosynthetic precursor: For porphyrins (haem), purines (DNA/RNA), creatine, and glutathione.

🍽️ Absorption & Bioavailability

🇦🇺 Australian NRVs (NHMRC)

• No specific NRV (RDI/AI) for glycine
• Adequate protein intake ensures sufficient supply in most individuals

🥗 Food Sources

• Meat, poultry, fish (especially connective tissue cuts)
• Dairy products
• Eggs
• Soy, legumes, seeds, nuts
• Gelatin, bone broth → particularly high glycine content

Diets low in collagen-rich foods may under-supply glycine relative to body needs.

🧪 Testing & Monitoring

• Plasma amino acid profiling (specialist/research setting).
• ❌ Not a routine GP pathology test in Australia.

🔄 Interactions

• ➕ Works with cysteine and glutamate to form glutathione.
• ➕ Requires folate & vitamin B12 for one-carbon metabolism.
• ⚠️ Supplemental glycine may enhance sedative effects of CNS depressants.

📊 Evidence Snapshot

• ✅ Established: Essential for collagen stability, neurotransmission, detoxification, and biosynthesis.
• ⚖️ Emerging: Supplemental glycine studied for sleep quality, metabolic health, and inflammatory conditions — promising, but not standard therapy.