Glycine is highlighted as an underrated supplement with significant benefits for sleep and longevity. It helps improve sleep quality by lowering core body temperature, acting on GABA pathways, and supporting REM and deep sleep. Glycine is also linked to lifespan extension, cellular cleanup through autophagy, and balancing methionine levels, which can accelerate aging if excessive. It supports metabolic health by reducing fasting blood sugar and insulin levels, enhances vascular function, and aids in collagen turnover for skin and joint health. Additionally, glycine can help preserve muscle and promote fat loss during calorie restriction. It is affordable and effective, with recommended doses ranging from 3 to 5 grams daily, or up to 20 grams if the diet is high in methionine. Glycine can be taken before bed for sleep benefits or during the day for general health benefits. It is naturally found in foods like chicken skin, fish skin, and gelatin, but supplementation can be beneficial due to common deficiencies.