Glycine and sleep: how this amino acid may help you fall asleep

Glycine is the smallest and simplest amino acid. Unlike other nutrients commonly associated with sleep, such as magnesium or melatonin, glycine remains relatively little known to the general public, even though it plays a central role in many bodily functions.

The body naturally produces glycine, notably from other amino acids. It is also found in food, particularly collagen-rich foods such as bone broth, gelatine, meat and fish, especially the skin and cuts rich in connective tissue. It is involved in collagen formation and the production of glutathione, an important antioxidant, and acts as an inhibitory neurotransmitter in the central nervous system[1][2].

It is this last point that has attracted researchers’ interest because of its role in sleep. Glycine acts as an inhibitory neurotransmitter in the central nervous system, meaning it helps calm neuronal activity rather than stimulate it.

Several studies have examined the effects of taking glycine before bed, particularly in people who report that their sleep is not restorative. The available findings suggest several possible mechanisms.

The best-documented effect concerns body temperature. Falling asleep naturally is accompanied by a slight drop in core body temperature, a physiological signal that prepares the body for sleep. Animal studies have helped identify the mechanism involved: by acting on certain receptors in the nervous system, glycine may promote the widening of peripheral blood vessels and thereby accompany this drop in temperature[3]. Human studies examining perceived sleep quality point in the same direction[4].

Another possibility involves serotonin: in animal studies, administering glycine increases the release of this neurotransmitter in certain areas of the brain. Serotonin is involved, among other things, in regulating mood and sleep-wake cycles[5]. In humans, the available trials mainly show a shorter time to enter slow-wave sleep, the phase considered the most restorative part of the night, without changing the proportion of the night spent in that phase[6].

In studies involving volunteers whose sleep was partially restricted, taking glycine before bed was associated with an improvement in perceived sleep quality and greater alertness the following day[7].

Good sleep can never be taken for granted, and certain stages of life may make it harder for some women.

During pregnancy

Sleep can be disrupted during pregnancy, even from the first few weeks. Hormonal changes, particularly rising progesterone levels, alter sleep-wake cycles and can lead to daytime sleepiness alongside more frequent waking at night. Physical discomfort may also increase as the trimesters pass. This can mean difficulty finding a comfortable position, lower back tension, a more frequent need to urinate or acid reflux when lying down.

Expectant mothers may also feel some anxiety about giving birth or the arrangements ahead, adding to these physical disruptions. As with postpartum and perimenopause, it is often staying asleep, rather than falling asleep, that becomes more difficult.

For new mums

The first few months after a baby arrives almost always bring broken sleep. Night-time breastfeeds, the baby waking and the need to be available at any time of night can profoundly disrupt usual sleep patterns. When this sleep debt builds up over weeks or even months, it can make falling asleep harder, even during the few opportunities to rest. The reason is simple: the body stays alert, ready to respond to the slightest signal.

During perimenopause and menopause

At this stage, hormonal fluctuations, particularly the gradual decline in oestrogen, can disrupt sleep. Night-time hot flushes, sweating, frequent waking in the middle of the night and difficulty getting back to sleep are commonly reported symptoms. Interrupted sleep can affect the whole day, potentially causing tiredness, irritability and difficulty concentrating.

In all three cases, the common thread is interrupted sleep rather than a real difficulty falling asleep. It is precisely this process of falling asleep, as well as sleep quality, that glycine is being studied extensively for.

Glycine is generally taken in the evening, around 30 minutes to 1 hour before bed, separately from meals. It comes in several forms: as a pure powder to dissolve in a glass of water, or in formulations combining several complementary active ingredients.

It can be combined with plants traditionally used for relaxation, such as chamomile, recognised for contributing to good sleep, or lemon balm. This is the approach behind Mama Dreams, a supplement in ampoules to dilute, combining glycine, chamomile extract and lemon balm extract, without melatonin. Designed to fit easily into an evening routine, Mama Dreams has been formulated to be compatible with pregnancy, breastfeeding, assisted reproduction and menopause, making it an option suited to many women. 

As with any food supplement, glycine is no substitute for good sleep habits. Limiting screen time in the evening, keeping regular bedtimes where possible and establishing a calming bedtime ritual remain essential, particularly when sleep is already being tested by the arrival of a newborn or symptoms of perimenopause. Glycine can support this routine, but cannot replace it.

The complementary role of magnesium

Another important ally for sleep, magnesium is often paired with glycine in an evening routine. It contributes to the normal functioning of the nervous system and to a reduction of tiredness and fatigue, making it a natural complement to glycine’s potential role in falling asleep. This is the combination Jolly Mama has chosen for Mama Relax, a powder to dissolve that provides 3 g of glycine and 100 mg of magnesium per dose, with no added sugar and a neutral taste. Designed for moments of relaxation at the end of the day, this formula is compatible with pregnancy and breastfeeding.

If you are currently receiving treatment, or are unsure because of your individual circumstances, we recommend seeking advice from a healthcare professional before starting a course of supplements.