Glycine vs Taurine

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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Mechanism

Taurine is a sulfonic acid amino acid (not incorporated into proteins) with diverse physiological roles. It is the most abundant free amino acid in excitable tissues (heart, brain, retina, muscle). Mechanisms: GABA-A receptor agonism (inhibitory neurotransmission), glycine receptor agonism, osmoregulation (cell volume regulation via taurine transporter TauT), bile acid conjugation (taurocholate formation for fat digestion), calcium handling in cardiomyocytes (modulates RyR2/SERCA2a), mitochondrial protein synthesis (taurine modification of mitochondrial tRNA), and potent antioxidant (directly scavenges HOCl, stabilizes membranes). Recently identified as a longevity-associated molecule — taurine levels decline with age and supplementation extends lifespan in mice.

Standard Dosing

1000-3000mg daily

Timing

Flexible. Evening preferred for sleep/relaxation benefits. Pre-workout for cardiac and exercise performance benefits.

Cycle Duration

ongoing

Side Effects

• Generally extremely well-tolerated
• Mild GI discomfort
• Drowsiness at high doses
• Rare: hypothermia in preclinical data

Contraindications

• Bipolar disorder on lithium (monitor levels)
• Severe renal impairment
• Caution with severe renal impairment

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