Collagen (Type I, II, III) vs Glycine

Mechanism

Hydrolyzed collagen peptides are absorbed as di- and tripeptides (primarily hydroxyproline-proline and hydroxyproline-glycine) via PepT1 transporters in the small intestine. These bioactive peptides accumulate in skin, cartilage, and bone where they stimulate fibroblast proliferation and extracellular matrix synthesis by upregulating collagen gene expression (COL1A1, COL3A1). They also inhibit MMP (matrix metalloproteinase) activity that degrades existing collagen, and stimulate hyaluronic acid production by dermal fibroblasts.

Standard Dosing

10-20g hydrolyzed collagen peptides daily

Timing

Any time; often added to morning coffee or post-workout shake. For joint support, take with vitamin C 30-60 min before exercise. Type II collagen (undenatured, UC-II) taken on empty stomach.

Cycle Duration

ongoing (minimum 8-12 weeks for visible results)

Side Effects

• Mild bloating
• GI discomfort
• Unpleasant taste
• Rare: calcium elevation (if calcium-containing marine source)
• Feeling of fullness

Contraindications

• Fish/shellfish allergy (if marine-sourced)
• Phenylketonuria (collagen contains phenylalanine)
• Histamine intolerance (bone broth collagen may be high in histamine)

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Mechanism

Glycine is the simplest amino acid with profound neurological and metabolic roles. It is an inhibitory neurotransmitter acting at glycine receptors (strychnine-sensitive) in the brainstem and spinal cord, inducing a drop in core body temperature that facilitates sleep onset. It is also an obligatory co-agonist at the NMDA receptor glycine binding site, modulating excitatory neurotransmission. Metabolically, glycine is the rate-limiting amino acid for glutathione synthesis (glutathione = glycine + cysteine + glutamate), a key substrate for collagen synthesis (every 3rd amino acid), essential for creatine synthesis, bile acid conjugation, heme synthesis, and one-carbon metabolism.

Standard Dosing

3-5g daily

Timing

3g before bed for sleep (core body temperature reduction). Divided doses during day for glutathione support. Powder in water has a mildly sweet taste.

Cycle Duration

ongoing

Side Effects

• Mild drowsiness
• Soft stools at high doses
• Nausea (rare)
• Generally extremely well-tolerated

Contraindications

• Very few absolute contraindications. Caution in severe renal disease.

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