Glycine is a conditionally essential amino acid that improves sleep quality and lowers core body temperature

Japanese researchers (Bannai and Kawai) conducted a series of double-blind placebo-controlled studies demonstrating that 3 g of glycine taken before bed reduced time to sleep onset, increased slow-wave sleep duration, reduced daytime sleepiness, and improved self-reported sleep quality and next-day cognitive performance. The mechanism involves glycine's action on brainstem neurons that mediate peripheral vasodilation — increasing blood flow to the hands and feet, which facilitates the core body temperature drop required for sleep initiation.

Practical Use

• 3 g glycine in water 30–60 minutes before sleep — the studied dose
• Powder form is cheapest; capsules are convenient but require multiple capsules for 3 g
• No known adverse effects at this dose; higher doses may cause mild GI discomfort
• Synergises with magnesium glycinate — glycine bound to magnesium provides both simultaneously
• Bone broth, gelatine, and collagen peptides are dietary glycine sources