Glycine for improving slow-wave (deep) sleep

A recent study on sleep and dementia points out (once again) that sleep is essential for good health in aging. The study found that decreased sleep, such as 6 hours or less per night, during your 50s and 60s increases the risk of dementia in your later decades by 30%.

Quality sleep is foundational for healthspan

Prioritizing sleep is one of those foundational things that everyone needs to do for quality health. Yes, there are the rare mutations that decrease your need for sleep, but if you aren’t one of the 1 in 10000 people who carry the DEC2 mutation, you need to get around 7.5 or 8 hours of sleep a night.

Amount of sleep: The first step, of course, is to plan enough time for sleep. Parents of little ones know how important it is to plan for the right amount of sleep. But somehow as adults, we sometimes tend to disregard the simple math on this. When my Oura ring first told me to start getting ready for bed at 9:15, I was surprised. But since I normally get up around 5:45, Oura was just doing the simple math of subtracting 8 hours and then giving a half-hour buffer to brush my teeth and wind down to sleep.

Sleep quantity is a fairly simple metric…but everyone knows that the quality of sleep also affects how you feel the next day.

When you sleep, your brain activity goes through several stages. You will have segments of light sleep, REM sleep, and slow-wave sleep.

More slow-wave sleep is linked to better response time and accuracy in cognitive tests the next day.[ref] One of the problems with aging is that slow-wave sleep decreases and becomes more fragmented. This slow-wave sleep loss has links to cognitive decline and to higher amyloid-beta levels.[ref][ref] Animal research points to a possible benefit for Alzheimer’s prevention with solid slow-wave sleep.[ref]

How can you increase your slow-wave sleep?

Glycine before bed may help increase your sleep quality and the time spent in slow-wave sleep. Glycine is an amino acid used throughout the body in many different ways. Your body naturally produces glycine (avg. of 45g per day), and you also get some from your diet (avg. 3-5g per day). In the central nervous system, glycine acts as an inhibitory neurotransmitter via glycine receptors in certain types of neurons. Additionally, glycine and glutamate act together in the brain in certain types of excitatory neurons.[ref]

Research on glycine for sleep quality:

Let’s take a look at the studies on glycine for sleep quality:

Improves sleep quality: 3g of glycine before bed improved sleep quality, sleep efficacy, and how quickly the participants got into slow-wave sleep.[ref]

Reduces fatigue the next day: In study participants who were sleep restricted for a few nights, 3 g of glycine significantly reduced fatigue the next day. The glycine did not affect melatonin production nor the expression of core circadian clock genes.[ref]

Drops overnight body temperature: Glycine supplementation before bed also decreases core body temperature. The drop in core body temperature is one of the circadian cues for sleep.[ref]

So what is going on in the brain when you take glycine at night?

When you take glycine as a supplement, it can easily pass across the blood-brain barrier to be used in the brain.

Glycine is a co-agonist with glutamate as a neurotransmitter in certain areas of the brain. NMDA receptors in neurons are activated by glutamate and glycine when certain conditions are met. (The NMDA receptors also activate with certain psychoactive drugs, ketamine, and alcohol.)[ref]

One area of the brain that has NMDA receptors is the suprachiasmatic nucleus, the region of the hypothalamus responsible for your circadian rhythm. Animal research shows that activation of these NMDA receptors by glycine decreases body temperature at night and is sleep-promoting.[ref]

Where can you get glycine?

Collagen and gelatin are excellent dietary sources of glycine. If you drink a hot beverage, such as herbal tea, before bedtime, you could dissolve collagen or gelatin into your tea. Check the label on your collagen or gelatin to see how much glycine is in a scoop.  For example, Zint collagen from grass-fed cows has around 5g of collagen per two-tablespoon serving. It dissolves fairly easily in both cold and warm drinks.

Glycine supplements are also cheap and readily available. You can get it in a powdered form, and the taste is just mildly sweet. Add it to water or another beverage to take glycine powder before bed. Glycine is also available in 1g capsules.  Personally, I like the powdered form so that I’m not taking unneeded cellulose capsules and because it is cheaper per serving.

Our ancestors likely consumed quite a bit more glycine in their diets than we do today. Traditionally, the whole animal was used for food, with the bones and other bits being incorporated into broths and stews. Bone broth is high in glycine due to the gelatin and collagen content. Most population groups have traditional recipes that are high in glycine such as fish head soup, ham hocks, or tripe. Congealed puddings, jellied luncheon meats, and gelatin desserts were also popular.  As a kid, I remember my mom making Knox blocks with grape juice as a treat. Knox gelatin is, of course, high in glycine.

Safety data for glycine:

While glycine is an endogenous amino acid, its role as an excitatory neurotransmitter (along with glutamate) means that there is a limit to what a person should take.

In rats, the toxicity dose (LD50) is 7930 mg/kg. Thus, while it is a fairly safe amino acid to supplement with, like pretty much everything, there is a maximum dose.

Clinical trials of glycine for sleep usually use around 3g/night. Other clinical trials, though, have used doses up to 0.8g/kg in schizophrenic patients (split into 2-4 doses).  For a 150 lb adult, 0.8g/kg would be over 50g. Other clinical trials for patients with schizophrenia used 15g-30g/day. While these doses explain the safety of glycine supplementation at higher amounts, the positive effects on sleep quality are likely found in the 3-5g range.

The one negative effect that I found for glycine is that it may inhibit wound healing. The inhibition of angiogenesis by glycine slows the growth of blood vessels, which could be a negative if you have a wound. On the other hand, this may slow the growth of tumors.[ref]

More to read:

Glycine plus NAC to boost glutathione
A high dose glycine plus n-acetyl cysteine supplement increased glutathione production in older adults. This reduced oxidative stress and increased mitochondrial function.