At a glance:
- Magnesium improves sleep quality primarily through the GABA system and is most effective in people with magnesium deficiency.
- Glycine (3 g before bedtime) helps you reach deep sleep sooner and reduces next-day fatigue.
- Melatonin reduces the time it takes to fall asleep by an average of 7 minutes and is best suited to circadian rhythm disorders.
- The three substances can be combined, but first it is worth assessing which deficiency is most likely in your case.
Sleep supplements have become increasingly popular in sports and health communities, but choosing between them calls for an evidence-based approach. Magnesium, glycine and melatonin work through three different mechanisms, each with its own strengths and applications. This overview summarizes the clinical evidence to help you find the sleep supplement that best suits your needs.
Which sleep supplements have been studied most extensively?
The three most extensively studied sleep supplements are magnesium, glycine and melatonin. Each works through a different mechanism:
- Magnesium works mainly by activating GABA receptors and inhibiting NMDA receptors, calming an overactive nervous system.
- Glycine is an inhibitory amino acid that lowers body temperature and helps you reach deep sleep sooner.
- Melatonin is a hormone that signals the day–night cycle to the brain – its production increases as darkness falls.
If you are looking for a comprehensive overview of supplements for athletes, we recommend reading the Supplements for athletes guide, which also covers substances that support recovery.
How does magnesium improve sleep?
Magnesium is a mineral involved in more than 300 enzymatic reactions. Its most important role for sleep is activating GABA receptors: GABA is the main inhibitory neurotransmitter, reducing brain excitability and helping you fall asleep. Magnesium also inhibits NMDA receptors, which otherwise keep the nervous system on high alert.
A double-blind study in older adults found that taking 500 mg of magnesium oxide daily for 8 weeks produced statistically significant improvements in sleep onset latency, sleep efficiency and sleep duration (Abbasi et al., 2012). An earlier study in adults with low magnesium status confirmed that supplementation shortened the time it took to fall asleep and reduced nighttime awakenings (Nielsen et al., 2010).
You can find more information about magnesium’s role in the human body in the article Magnesium – a vital mineral.
How much glycine should you take for sleep, and when?
Glycine is an essential amino acid found in abundance in collagen and gelatin. The standard dose used in sleep studies is 3 grams taken 30–60 minutes before bedtime.
Japanese researchers showed that 3 g of glycine significantly improved subjective sleep quality and reduced next-day fatigue and daytime sleepiness (Bannai and Kawai, 2012). Polysomnographic measurements confirmed that glycine shortened the time it took to reach deep sleep (SWS) and lowered body temperature – an important physiological prerequisite for falling asleep (Yamadera et al., 2007).
Glycine has an advantage over melatonin in that it is not addictive, does not disrupt hormone levels and does not cause morning grogginess. This also makes it suitable for long-term daily use.
When is melatonin the best sleep supplement?
Melatonin is a hormone produced by the pineal gland. Its secretion increases as darkness falls, and it regulates your circadian rhythm. The primary indication for exogenous melatonin is circadian rhythm disorders, rather than chronic insomnia.
A meta-analysis of 19 randomized controlled trials found that melatonin reduces the time it takes to fall asleep by an average of 7.06 minutes and improves overall sleep quality compared with a placebo (Ferracioli-Oda et al., 2013). An earlier systematic review confirmed melatonin’s effectiveness for jet lag and shift work, but noted that its effect in treating chronic primary insomnia is modest (Brzezinski et al., 2005).
The World Health Organization emphasizes that sleep disorders are a major public health concern and that opportunities to improve sleep hygiene should be assessed before using supplements (see the WHO mental health page). The European Food Safety Authority (EFSA) has confirmed that 1 mg of melatonin before bedtime helps reduce the time it takes to fall asleep when experiencing jet lag.
How do you choose the right sleep supplement?
Your choice depends on the nature of your symptoms and your lifestyle:
| Situation | Best choice |
|---|---|
| General restlessness, stress, muscle weakness | Magnesium (glycinate) |
| Poor sleep quality, morning fatigue | Glycine 3 g |
| Jet lag, shift work, late chronotype | Melatonin 0.5–1 mg |
| Intense training and poor sleep | Magnesium + glycine in combination |
If you have questions about balancing stimulants and sleep supplements, read the Energy drink comparison article, which discusses caffeine’s effects on sleep.
Important note: none of the sleep supplements listed replaces advice from a doctor treating a chronic sleep disorder. If sleep problems persist for more than four weeks, the Estonian Health Board recommends consulting your family doctor.
References
- Abbasi B et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences. PMID: 23853635
- Nielsen FH et al. (2010). Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep. Magnesium Research. PMID: 21199787
- Bannai M, Kawai N. (2012). New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep. Journal of Pharmacological Sciences. PMID: 22227731
- Yamadera W et al. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms. DOI: 10.1111/j.1479-8425.2007.00262.x
- Ferracioli-Oda E et al. (2013). Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLoS ONE. PMID: 23691095
- Brzezinski A et al. (2005). Effects of exogenous melatonin on sleep: a meta-analysis. Sleep Medicine Reviews. PMID: 15649737
Frequently asked questions
Can you take magnesium and melatonin together?
Yes, these two substances work through different mechanisms and are safe to combine. Magnesium supports the GABA system, while melatonin supports your circadian rhythm – together, they may offer an additional benefit.
How quickly does magnesium start improving sleep?
Clinical studies found noticeable results within 4–8 weeks. The effect of a single dose is modest – magnesium works through ongoing supplementation, rather than a one-off dose.
When is the best time to take sleep supplements?
Glycine and melatonin are best taken 30–60 minutes before bed. You can take magnesium with dinner or just before bed – taking it on a full stomach reduces gastrointestinal irritation.
Is melatonin addictive?
Studies to date have not shown physical dependence, but long-term use may reduce your body’s own melatonin production. You are therefore advised to use the lowest effective doses (0.5–1 mg) and avoid taking it every day for an extended period unless needed.
Which forms of magnesium are best for supporting sleep?
Magnesium glycinate is better absorbed and gentler on the digestive tract than magnesium oxide. Magnesium taurate and malate are also well absorbed and have a calming effect. Magnesium oxide is often used in studies, but is more likely to cause digestive problems.
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