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Leonid Kim MD - GLYCINE: The Cheapest Anti-Aging Supplement That Actually Works

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Author: Leonid Kim MD
Categories: Health
Tags: health
Views: 2 · Last viewed: 2026-10-16 15:01 UTC

Short Summary

Main recommendation: Take glycine, about 3 g 30 to 60 minutes before bed, mainly for sleep; if there are metabolic issues, consider GlyNAC (glycine plus N-acetylcysteine) instead. The speaker frames glycine as a key building block of glutathione, the body's main antioxidant, and notes that supporting evidence for sleep is strongest while GlyNAC data are small and short-term.

Key Points

  • Glycine supports glutathione synthesis, along with glutamate and cysteine; glycine and cysteine are often the rate-limiting factors.
  • The sleep evidence is strongest: glycine may reduce sleep onset latency and improve next-day alertness and cognition.
  • The proposed sleep mechanism involves lowering core body temperature via vasodilation (through NMDA receptor activity in the suprachiasmatic nucleus) and quieting orexin-driven wake signals.
  • A 2022 review suggested glycine may help components of metabolic syndrome, since glycine levels are often lower in obesity, insulin resistance, and metabolic disorders.
  • GlyNAC is proposed because cysteine is unstable and often in short supply; NAC supplies it in a usable form. A 16-week older-adult trial reported gains in muscle strength, gait speed, and cognition, but the studies were small and short.

Details Worth Noting

  • Concrete instructions: For glycine alone, the most studied dose is 3 g taken about 30 to 60 minutes before sleep; it dissolves easily in water and is usually well tolerated. For GlyNAC, published human studies used 100 mg/kg of glycine and 100 mg/kg of NAC per day (about 7 g each for a 70 kg person), split into two doses, and people commonly start around 3 g per day and increase gradually. Choose glycine alone if young and healthy; consider GlyNAC if there is insulin resistance, diabetes, pre-diabetes, PCOS, fatty liver, high blood pressure, high cholesterol, chronic inflammation, or an autoimmune condition. Talk to a doctor before changing supplements.
  • Schizophrenia studies used up to 800 mg/kg/day of glycine (mean about 61 g daily, range 40 to 90 g), which the speaker considers small, short-term, and not safe to extrapolate; he does not recommend mega-dosing until more human safety data exist.
  • Dr. Kim notes that the schizophrenia high-dose studies (up to 800 mg/kg/day) appeared fairly well tolerated with no major safety issues, though there are case reports of neurobehavioral changes and sensory overload, and animal models raised possible cardiovascular and neurological toxicity concerns; he cautions against extrapolating these small, short-term studies.
  • NAC alone can cause nausea and diarrhea, and caution is advised with a history of asthma or allergies.
  • The speaker says glycine is conditionally essential in metabolic disorders because the body may not produce enough.

Bottom Line

Glycine is a low-cost, well-tolerated option with the strongest evidence for sleep, while GlyNAC is a more speculative option for metabolic or inflammatory conditions that needs larger, longer studies; medical guidance is advised before use.