Glycine: The Sleepy Amino Acid

Getting harder to catch ZZZs? Mr. Sandman not bringing you as many dreams? Hold onto your eye mask and don’t say goodnight to quality slumber just yet. It might be time to try the sleepy amino acid: glycine.

When we think of supplements that are helpful for sleep, glycine probably isn’t the first nutrient that comes to mind. And certainly, favorites like melatonin and valerian root deserve a place on your bedside table. But you might want to leave a little room for glycine. This amino acid plays nicely with other sleep supplements but also packs a powerful punch on its own. Not only that, with its many whole-body health benefits, this nutrient supports many of the functions that keep us healthy—day and night.

Here’s how it works.

What is glycine?

Though it is technically considered a non-essential amino acid, since the body produces it from other amino acids, when it comes to its health benefits, it would be hard to call glycine anything less than an “essential”! Functioning as both an amino acid and a neurotransmitter, glycine helps your body create proteins (including collagen, an anti-aging essential) that help support connective tissue health. In this regard, glycine is no different from other amino acids.

But glycine benefits go far beyond that, positively impacting metabolic health, healthy protein synthesis and skin and tissue health. It even helps fight oxidative stress. And while it dips its toes in all sorts of health benefits, perhaps one of the best roles glycine supplements play is in supporting sleep.

5 benefits of glycine supplements

Glycine is an inhibitory neurotransmitter, which simply means that it blocks messages from being passed along to next brain cell. These types of neurotransmitters are generally responsible for inducing sleep and calming the mind. Due to its location in the central nervous system (specifically the brain stem and spinal cord), glycine helps with the processing of motor and sensory information that governs movement, vision and auditory signaling. One of the very important messages glycine sends the brain is to tell it to wind down around bedtime.

Here are five specific ways glycine supplements support quality rest:  

1. Supporting overall sleep quality—While the amount of shuteye you get is undeniably important, making sure that you’re achieving optimal sleep quality is crucial, as low quality sleep can impact both your mental and your physical health. Enter glycine. In one study, 19 female subjects who had previously reported less than desirable sleep quality were given 3 g of glycine before bedtime. Using a questionnaire along with a fatigue checklist, the study found that the amino acid helped fight morning fatigue and improve overall sleep quality in the subjects compared to placebo—a benefit that you shouldn’t sleep on!   
2. Falling asleep quicker—Sleep onset latency, or SOL, is the time it takes for a person to fall asleep once all their lights are off, and is a major indicator of quality of sleep. On average, a healthy person takes between 10-20 minutes to fall asleep. But for those who may struggle with sleepiness (and those who opt to scroll on their phone once they hit the sheets), glycine can help with the amount of time it takes for sleep onset to take hold. According to one study of healthy adults who took 3 grams of glycine an hour before bed, it was found that sleep onset latency was shorter, which means less time to reach those sweet dreams!
3. Reaching deep sleep quicker—Slow-wave sleep (SWS), aka deep sleep, is traditionally known as stage 3 of sleep and is characterized by non-rapid eye movement and low-frequency brain waves (commonly known as delta waves). SWS is important to achieve as it benefits several aspects of health, and is the stage of sleep that is necessary for waking up refreshed in the morning. This is where glycine comes in. The same study that recorded SOL and how fast the subjects fell asleep also recorded a shorter duration in onset latency of slow wave sleep after ingesting 3 grams of glycine—meaning that not only will this nutrient be having you sleeping sooner, it will have you sleeping deeply sooner, too.



4. Fighting daytime sleepiness—Ever get your seven to nine hours of restful sleep, but just can’t seem to shake the daytime drowsiness, even after your second or third cup of coffee? This is where glycine comes in! It can help fight the midday (or let’s face it, sometimes mid-morning) drowsiness that we all experience. Prepare yourself to hit the snooze button no longer! During one crossover trial, 11 volunteers that reported unsatisfactory sleep as measured by the Pittsburgh Sleep Quality Index were given glycine. Daytime sleepiness was assessed over five different times of the day, and it was found that daytime sleepiness was improved in the morning, as measured by a visual analog scale. Study participants that consumed glycine the previous night also improved performance in a memory recognition task.
5. Cognitive performance—It should come to no surprise that when you’re not getting your best sleep, it can impact your brain health. Supporting healthy sleep is a great way to keep your noggin sharp for the long haul. In fact, one study saw positive results in cognitive function during periods of sleep restriction when glycine was consumed 30 minutes before bed.

How to supplement with glycine

Glycine should be taken on an empty stomach at bedtime. Depending on the dose and your specific needs, it can be taken one to three times daily (don’t worry—taking it during the day will not cause drowsiness). It may benefit those seeking improved sleep to take high dose glycine 1-3 times daily. However, keep in mind that everybody and every body is different, so it’s important to check in with yourself and your healthcare practitioner periodically if you think you need more or less of this amino acid for optimal health benefits, and also if you have any questions or concerns about long term use of glycine supplements.

Pro tip: If you want to optimize your dietary glycine intake alongside glycine supplementation, it can be found in several foods, including high protein meat and fish, spinach, bone broth, and even legumes.

Can I take melatonin and glycine together?

Melatonin is well known, and for good reason! A superstar hormone for helping support the body’s sleep wake cycles, aka circadian rhythms, melatonin is often found as a standalone supplement. But can you combine it with other supplements to maximize its benefits?

Good news! It’s unlikely that the combination of melatonin and glycine is unsafe to use. To produce melatonin, the body needs serotonin. And, there is some preclinical research showing that glycine stimulates the release of serotonin. So, if you are taking these two together, it stands to reason that it may be even easier to fall asleep and stay asleep with this combination.

That being said, it’s important to discuss any possible questions or concerns you may have with your healthcare provider about the proper dose and use when taking these two nutrients in tandem.

Other supplements you can take with glycine for sleep

Similarly to taking melatonin with glycine, there doesn’t appear to be known side effects for other sleep supplements in combination with this amino acid. Just be sure to always speak to your healthcare practitioner before introducing something new.
Here are a few supplements we like:

• Lemon balm—Lemon balm is a great option for those who want to support their sleep both without melatonin and without dairy byproducts. Lemon balm has been studied for its positive impacts on healthy sleep quality, and its benefits are enhanced by the presence of honokiol and chamomile.
• L-theanine—While it isn’t technically a sleep supplement, l-theanine, another amino acid, is known best for supporting a healthy stress response and overall well-being, as well as promoting a calm and relaxed state of mind, two essential aspects of helping you wind down in preparation for bedtime, making it complementary to glycine’s benefits.
• Bioactive milk peptides—Have you ever drank a warm glass of milk before bed to help you fall asleep? That’s the idea behind this milk protein extract that will have you sleeping in no time!
• Tryptophan—While it may only be a rumor that the tryptophan in turkey causes that mid-holiday nod off, there is still some power in this essential amino acid. L-tryptophan is known for crossing the blood-brain barrier, benefiting both serotonin and melatonin production, thus being a good option for sleep.

4 other ways to achieve healthy sleep

Sleep is one of the most important aspects of a healthy lifestyle, and fortunately there ways to make sure you’re maximizing your well-being beyond glycine supplementation. To be sure you’re giving yourself the best possible chance of high-quality shut-eye, follow these dos and don’ts.

1. DON’T be a night owl at the gym. Avoid exercise at least an hour before bed to keep your heart rate down.
2. DO put your phone away. Stay away from screens and other blue light emitting devices at least two hours before bed.
3. DO focus on healthy eating. Good options to include in your healthy diet include fresh fruits and vegetables, lean poultry and meat, protein rich foods, and healthy fats. Adding dietary supplements to your diet to address your various health needs is also important for staying healthy, whether you’re awake or asleep.
4. DO stay cool—literally! The Sleep Foundation suggests that an optimal temperature for quality sleep is approximately 65 degrees Fahrenheit. Since we tend to experience a small dip in core body temperature in the evening, keeping the thermostat low can help keep your body temperature right where you want it for bedtime. 

While there are other ways to optimize your nighttime routine, keeping these tips in mind will have you drifting off to dreamland in no time!

References

• Bannai, Makoto, et al. “New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep.” J Pharmacol Sci. January 2012. https://pubmed.ncbi.nlm.nih.gov/22293292/
• Bannai, Makoto, et al. “The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers.” Front Neurol. April 2012. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3328957/
• Gratwicke, Madeline, et al. “Nutritional Interventions to Improve Sleep in Team-Sport Athletes: A Narrative Review.” Nutrients. May 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8150598/
• Inagawa, Kentaro, et al. “Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep and Biological Rhythms. February 2006. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1479-8425.2006.00193.x
• Pacheco, Danielle. “The Best Temperature for Sleep.” Sleep Foundation. September 2022. https://www.sleepfoundation.org/bedroom-environment/best-temperature-for-sleep
• Wang, Weiwei, et al. “Glycine metabolism in animals and humans: implications for nutrition and health.” Amino Acids. April 2013. https://pubmed.ncbi.nlm.nih.gov/23615880/
• Yamadera, Wataru, et al. “Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes.” Sleep and Biological Rhythms. March 2007. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1479-8425.2007.00262.x