L-Threonine for Health & Longevity - Quick Reference Sheet
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L-Threonine for Health & Longevity

Created on 06/15/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 4.8 – Audit

An essential amino acid from protein foods, central to the gut's protective mucus layer and a raw material for the calming molecule glycine. The strongest human evidence shows a modest drop in measured muscle stiffness in neurological conditions. Longevity and gut benefits rest on animal data. Inexpensive and well tolerated, but largely unproven in people. (Full Review)

Protocol

Dose
1–7.5 g/day
Standard range for general/neurological use, often divided
Schedule
Split 2–3×/day
Maintains availability and minimizes GI load per dose
Timing
No superior time
Evening sometimes suggested for calming/sleep rationale
Time to effect
Muscle stiffness
Weeks
Measurable muscle-tone changes emerged over treatment periods of weeks
Gut/barrier
Not established
No validated time-to-effect in humans
Longevity
Not established
No validated time-to-effect in humans

Benefits

Contraindications
  • Pregnancy and breastfeeding
  • Significant hepatic impairment (Child-Pugh Class B or C)
  • Advanced chronic kidney disease (eGFR below 30 mL/min/1.73 m²)
  • Known rare inborn errors of amino acid metabolism
    •
Key Interactions
  • CNS depressants and antispastic medications (baclofen, tizanidine, benzodiazepines such as diazepam)
  • High-dose single amino acids
  • Glycine, serine
    •

Risk & Side Effects

  • High: [risks_high]
    •
  • Medium: [risks_medium]
    •
  • Low: Gastrointestinal upset; transient, non-specific liver and muscle enzyme elevations
    •
  • Speculative: Excess-intake and amino acid imbalance concerns; iron-handling effects
    •

Monitoring

Marker Target Why
AST (aspartate aminotransferase) ~10–26 U/L Detects liver/muscle stress
ALT (alanine aminotransferase) ~10–26 U/L Liver-specific enzyme baseline
Creatine kinase (CK) ~40–180 U/L (sex-dependent) Detects muscle enzyme elevation
Ferritin ~30–150 ng/mL (avoid high-normal extremes) Relevant to the iron/ferroptosis mechanism
Plasma amino acid panel (incl. threonine) Within reference range for threonine Confirms intake and rules out gross imbalance

Cadence: General use: every 6–12 months. Higher doses: recheck enzymes within first 4–8 weeks, then as clinically indicated.

Qualitative Assessment

  • Subjective muscle stiffness or ease of movement (relevant only to those with spasticity)
  • Sleep quality and sense of calm (if pursuing the speculative glycine-related rationale)
  • Gut comfort and bowel regularity (relevant to the mucin/barrier rationale)
  • General energy and well-being
  • Tolerability — absence of nausea, stomach upset, or headache
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.