Glycine and Sleep: How Collagen Might Help You Rest Better
Your body signals sleep onset through temperature. As core body temperature drops, your nervous system shifts from active to restful. Glycine is the amino acid that makes that temperature drop happen. Without it, your body temperature stays elevated. Deep sleep doesn't come.
Reviewed by Pedro Rodrigues, Agronomist · 
What is glycine and why you need it
Glycine is the smallest amino acid. Your body can synthesise it from other amino acids, but typically not in quantities sufficient for optimal function. Most people need to get glycine from food.
Glycine makes up roughly 30% of collagen.1 Collagen is the connective tissue in your skin, bones, tendons, ligaments, and the gelatinous parts of animals. When you eat bone broth, skin, joints, or gelatinous cuts of meat, you're eating collagen. Your digestive system breaks it down into amino acids, including glycine.
Glycine is unique among amino acids. It's not just a building block. It has specific effects on the nervous system and on body temperature regulation. These effects are what make it crucial for sleep.
How glycine lowers body temperature
Glycine promotes vasodilation, the widening of blood vessels.3 This is particularly pronounced in the extremities, hands and feet. When blood vessels in your hands and feet widen, blood flow increases to those areas. Your body radiates more heat from the periphery. Your core temperature drops.
This temperature drop is one of the primary signals for sleep onset. Your hypothalamus (the part of your brain that controls sleep-wake cycles) detects the falling core temperature and initiates sleep. If your core temperature stays elevated, this signal never arrives. You struggle to fall asleep or fall asleep shallowly.
Research shows that glycine supplementation before bed reduces the time it takes to fall asleep and increases sleep quality, particularly deep sleep stages (non-REM sleep).2 The effect is measurable. People report falling asleep faster and waking fewer times during the night.
Glycine allows your body temperature to drop. Temperature drop allows deep sleep to happen. No temperature drop, no deep sleep.
Glycine and the nervous system
Beyond its effects on temperature, glycine has direct nervous system effects. It binds to glycine receptors, particularly in the spinal cord and brainstem, reducing excitation. It's one of the few amino acids that actively calms the nervous system.
Glycine is also a precursor to glutathione, your body's master antioxidant.4 During sleep, your brain undergoes significant detoxification. Glycine supports this process. Better detoxification during sleep means better cognitive function and mood the next day.
Additionally, glycine is involved in the synthesis of creatine, which is crucial for energy production in cells, including neurons. Better neuronal energy means better sleep quality and better cognitive recovery during sleep.
From collagen to glycine
Collagen-rich foods are the natural source of glycine. Bone broth is the obvious one. A single serving (roughly 250 mL) contains 1-2 grams of glycine. Drink it daily and you'll get consistent glycine intake.
But bone broth isn't the only source. Skin from chicken, fish or pork carries collagen. Gelatinous cuts of beef, lamb, or pork (chuck, shank, brisket) contain it. Tendons, ligaments, connective tissue. These parts of the animal are glycine-rich.
If you eat nose-to-tail, including the gelatinous parts, drinking bone broth daily, you're getting substantial glycine. If you eat only muscle meat and avoid the collagenous parts, you're probably deficient.
Supplemental glycine powder is available and works. 3-5 grams before bed improves sleep quality. But food is better. Your body recognises whole food patterns and responds more robustly than to isolated amino acids.
How much you need
Research suggests 3-5 grams of glycine daily for sleep benefits.2 A single serving of bone broth provides roughly 1-2 grams. If you're eating collagenous animal foods regularly, you might be hitting 2-3 grams from food alone.
If you're also supplementing, 3 grams from a supplement plus 2 grams from food gets you to optimal levels. If you prefer to do it all through food, aim to include bone broth daily and eat a portion of collagenous animal food (braised meat, skin, etc.) most days.
More isn't necessarily better. Beyond 5-10 grams, glycine's sleep-promoting effects plateau. Very high intakes (above 15 grams) can cause mild digestive upset. Aim for the 3-5 gram range for sleep benefit.
The practical approach
Start with bone broth. A single serving (250 mL) in the morning or an hour before bed provides glycine along with minerals and other amino acids that support sleep. Do this daily for a week and notice sleep changes. The warmth also supports the parasympathetic shift toward sleep.
Add collagenous animal foods to meals. Braised beef short ribs. Chicken thighs with skin. Fish head soup. Oxtail stew. These foods taste good and provide glycine in food matrix rather than as an isolated supplement. The synergistic effects of the full nutrient package (glycine plus minerals plus other amino acids) often exceed what glycine supplementation alone provides.
If you want to be more precise, supplement 3 grams of glycine powder before bed. Mix it with warm water or bone broth. The effect is usually noticeable within 3-5 days. Consistency matters more than precision. Glycine benefits accumulate over time.
If you're currently sleeping poorly, don't expect one night of good nutrition to fix it. Your body needs consistent signalling. Sleep depth improves measurably within a week of consistent glycine intake, but reaches full effect within 4-6 weeks as your nervous system adapts and your core temperature regulation stabilises.
Glycine from whole foods is more reliable than from supplements alone, but glycine supplementation works. Use whichever approach fits your life.
Individual variation and timing
Some people notice sleep improvements within one night of glycine supplementation. Others need a week of consistent intake. This variance is normal and depends on how depleted your baseline glycine status is and how sensitive your nervous system is to amino acid shifts.
Timing matters. Glycine works best when taken 30 minutes to an hour before bed. This allows time for absorption and for the temperature-lowering effect to manifest as you're attempting sleep. If you take it immediately before bed, you might miss the window.
Glycine works synergistically
Glycine works best when paired with other sleep-supporting nutrients. Magnesium relaxes muscles and supports nervous system function. B6 supports neurotransmitter synthesis. Adequate carbohydrates in the evening (white rice, fruit, honey) stabilise blood sugar and support the shift toward parasympathetic dominance. Tryptophan-rich foods (turkey, eggs, cheese) provide the precursor for serotonin synthesis.
Glycine alone is helpful. Glycine plus magnesium plus these other nutrients is transformative. Think of it as layers: glycine lowers temperature, magnesium allows tension release, B vitamins allow neurotransmitter synthesis, carbohydrates signal safety. Together, they create the biochemistry of deep sleep.
The bottom line
Sleep depth is partly a matter of body chemistry. Your core temperature has to drop. Your nervous system has to relax. Glycine is the amino acid that enables both. You can't force deep sleep. But you can feed your body what it needs to fall into it naturally. Bone broth, collagenous meats, and glycine supplementation are the tools. Use them consistently, and your sleep will deepen.
References
- 1. Ricard-Blum S. The Collagen Family. Cold Spring Harbor Perspectives in Biology, 2011. PMC3003457.
- 2. Bannai M, Kawai N. New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep. Journal of Pharmacological Sciences, 2012. PMID 22293292.
- 3. Kawai N et al. The Sleep-Promoting and Hypothermic Effects of Glycine are Mediated by NMDA Receptors in the Suprachiasmatic Nucleus. Neuropsychopharmacology, 2015. PMC4397399.
- 4. Wang W, Wu Z et al. Glycine metabolism in animals and humans: implications for nutrition and health. Amino Acids, 2013. PMID 23615880.
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