Collagen is the most abundant structural protein in the human body, providing strength and elasticity to skin, bones, and connective tissues. While it has become widely known as a popular supplement for promoting joint health and a youthful complexion, a specific claim has emerged regarding its potential to enhance sleep quality. This theory suggests that ingesting collagen before bed may lead to more restorative rest, a benefit rooted in the protein’s unique amino acid composition.
The Key Mechanism: Glycine’s Influence on Sleep
The sleep-promoting effects associated with collagen are primarily due to the high concentration of one specific amino acid it contains: glycine. Collagen is composed of approximately one-third glycine, making it an extremely rich dietary source. Once ingested and absorbed, this amino acid plays a significant role in calming the central nervous system.
Glycine functions as an inhibitory neurotransmitter in the brain, meaning it reduces neuronal activity and helps quiet the mind in preparation for sleep. This calming effect is achieved by modulating receptors in the suprachiasmatic nucleus (SCN), the brain’s internal master clock that regulates the sleep-wake cycle. The ingestion of glycine allows it to cross the blood-brain barrier, directly influencing these neurological pathways.
A specific mechanism involves the body’s thermoregulation system, a process that must occur to initiate sleep. Glycine works to increase blood flow to the extremities (vasodilation), which facilitates the dissipation of heat from the core of the body. This subtle decrease in core body temperature is a natural physiological requirement for sleep onset. By supporting this cooling process, glycine signals to the body that it is time to transition into a restful state.
Scientific Evidence Supporting the Claim
Research has consistently focused on the effects of isolated glycine, as opposed to the full collagen protein, when investigating sleep benefits. In human studies, consuming a dose of pure glycine before bedtime has been shown to improve subjective sleep quality, even in individuals who report having persistently poor sleep. Participants noted that they felt more rested and refreshed the morning after taking the supplement.
Objective measures have also demonstrated that glycine can shorten sleep onset latency, which is the amount of time it takes to fall asleep. Furthermore, the intake of glycine has been associated with a significant reduction in daytime sleepiness and fatigue experienced the following day. These findings suggest that the amino acid supports a more restorative sleep state without the grogginess often linked to traditional sleep medications.
A more recent line of inquiry has examined the use of glycine-rich collagen peptides specifically. One randomized, crossover study involving physically active men with self-reported sleep complaints used 15 grams of collagen peptides, which provided approximately 3.5 grams of glycine. The results showed that collagen supplementation reduced both objective and subjective awakenings, suggesting a reduction in sleep fragmentation.
However, the same collagen study did not find improvements in other metrics like total sleep duration or overall sleep efficiency. This highlights a distinction where the benefit may lie more in maintaining continuous sleep rather than hastening the initial fall asleep time. It is important to note that much of the existing data, particularly for collagen peptides, comes from small-scale trials, but the strong evidence for reducing sleep fragmentation is a key finding that supports collagen’s use for sleep quality.
Supplementation Guidelines for Sleep Support
For individuals interested in trying collagen or glycine to support better sleep, timing and dosage are the most important practical considerations. The primary goal is to ensure the glycine is circulating in the bloodstream and reaching its peak concentration around the time you wish to fall asleep. This suggests taking the supplement approximately 30 to 60 minutes before your scheduled bedtime.
The effective dose observed in most human studies using pure glycine is 3 grams. Since collagen peptides are approximately one-third glycine, a comparable dose when using a collagen supplement is typically 15 grams. This higher collagen dose ensures the delivery of the 3 to 4 grams of functional glycine required to trigger the thermoregulatory and neurotransmitter effects.
Choosing between pure glycine powder and a full collagen peptide supplement depends on personal preference and desired secondary benefits. While pure glycine is a more direct and concentrated approach for sleep, the 15-gram collagen dose provides a wider spectrum of amino acids that may support skin, joint, and gut health. Consuming the supplement dissolved in a warm beverage, like water or caffeine-free tea, can also promote a relaxed state as part of a calming nightly ritual.