None of these four options has strong evidence for improving sleep in healthy, training men. Magnesium has a small meta-analysis in older adults showing faster sleep onset on low-quality evidence. Glycine has small human studies showing better subjective sleep and faster entry into deep sleep. Melatonin has more research than either, but the American Academy of Sleep Medicine suggests against it for chronic insomnia. DSIP is a research peptide whose human data are old, small and inconsistent, and it isn't approved for any use. For most lifters, sleep timing, training load and screening for sleep apnea will do more than any of the four.
The comparison
| Option | Best human evidence | What was measured | Status |
|---|---|---|---|
| Magnesium | Meta-analysis of 3 small RCTs in older adults | Sleep onset about 17 minutes faster; total sleep time not significantly changed | OTC supplement |
| Glycine | Small human studies (e.g., Yamadera 2007) | Subjective sleep quality; faster sleep onset and slow-wave sleep on polysomnography | OTC supplement |
| Melatonin | Many trials; AASM weak recommendation against it for chronic insomnia | Sleep onset and maintenance in insomnia | OTC supplement in the US |
| DSIP | Small, mostly older European studies with inconsistent results | Varied; not standardized | Research-use only; not FDA-approved |
Magnesium
The best summary is a 2021 systematic review and meta-analysis by Mah and Pitre in BMC Complementary Medicine and Therapies. It found three randomized trials of oral magnesium for insomnia in older adults, with 151 participants in total.
- Sleep onset latency: about 17.4 minutes faster with magnesium than placebo (95% CI −27.3 to −7.4 minutes).
- Total sleep time: about 16 minutes longer, but not statistically significant.
- Quality: all trials had moderate-to-high risk of bias, and the evidence was rated low to very low quality. The authors called the literature "substandard for physicians to make well-informed recommendations."
That's a modest signal in older adults with insomnia, not proof of better sleep in a 30-year-old lifter. Magnesium is cheap and generally well tolerated at supplement levels, though high intakes can loosen stools, and people with kidney disease should ask a doctor first. If you want to try it, magnesium glycinate is a commonly sold form.
Glycine
Glycine is an amino acid, and the most cited human study is Yamadera and colleagues, published in Sleep and Biological Rhythms in 2007. Volunteers who had been "continuously experiencing unsatisfactory sleep" took 3 g of glycine before bed. The study reported:
- improved subjective sleep quality and sleep efficacy,
- shorter latency to sleep onset and to slow-wave sleep on polysomnography, with no change in overall sleep architecture,
- less daytime sleepiness and better performance on a memory recognition task.
The appealing part for lifters is the faster entry into slow-wave sleep. The limits: it's a small study population, the record we checked doesn't give the sample size, and it hasn't been confirmed in large trials or in athletes. Glycine powder is inexpensive and tastes mildly sweet.
Melatonin
Melatonin is the most studied of the four, and it has the most awkward guideline position. The American Academy of Sleep Medicine's 2017 guideline on drugs for chronic insomnia lists melatonin, along with diphenhydramine, L-tryptophan and valerian, under a weak recommendation that clinicians not use them for sleep onset or sleep maintenance insomnia.
That doesn't mean melatonin does nothing. It means the guideline panel didn't find the benefit large enough for chronic insomnia. Melatonin is better understood as a timing signal for your internal clock than as a sedative, which is why it's often discussed for circadian problems rather than as a nightly knockout. If you work nights or travel across time zones for competition, ask a clinician about timing rather than just taking more. Our night-shift post covers the shift-work side.
DSIP (delta sleep-inducing peptide)
DSIP is a short peptide first described in the 1970s. Its human evidence consists mainly of small European studies, mostly from the 1980s, with inconsistent results. We weren't able to retrieve those original trial reports in full while writing this, so we're not quoting effect sizes. What we can say:
- DSIP isn't FDA-approved for any use.
- Research-grade DSIP isn't sold for human use and has no approved human dose.
- It was one of the peptides FDA's Pharmacy Compounding Advisory Committee reviewed in July 2026. Our DSIP after the advisory committee post covers how it fared and what it means.
- For tested athletes, unapproved peptides can fall under WADA's S0 non-approved substances category.
For the full profile, see our DSIP research page.
Magnesium: small meta-analysis, low-quality evidence, older adults. Glycine: small human sleep-lab studies. Melatonin: lots of research, a guideline that suggests against routine use for chronic insomnia. DSIP: old, small, inconsistent human data, and research-use only.
How to test a sleep supplement on yourself, fairly
If you want to try magnesium or glycine, make it an honest experiment rather than a vague impression:
- Change one thing at a time. Starting magnesium, a new bedtime and a deload in the same week tells you nothing.
- Keep a simple sleep diary for two weeks before and two weeks during: bedtime, rough time to fall asleep, wake-ups, and how rested you feel on a 1 to 10 scale.
- Treat wearable sleep stages with caution. Consumer devices estimate sleep stages and aren't a substitute for a sleep study, so look at trends rather than nightly deep-sleep numbers.
- Stop if it does nothing. A supplement that doesn't change your diary after a few weeks isn't worth taking.
What actually moves recovery sleep
For lifters, the biggest sleep problems are usually structural rather than chemical:
- Consistent sleep and wake times, including weekends.
- Caffeine timing. Pre-workout late in the day is a common culprit.
- Training load. Heavy blocks and late-evening sessions can make it harder to settle.
- A cool, dark, quiet bedroom.
- Screening for sleep apnea. Big, heavily muscled men with thick necks are not immune. Loud snoring, witnessed breathing pauses, or waking unrefreshed despite enough hours all deserve a sleep evaluation. Our sleep apnea post explains why.
- For chronic insomnia, cognitive behavioral therapy for insomnia (CBT-I) is the standard first-line treatment, ahead of any pill.
If you want to build around those basics, the sleep and recovery stack and the sleep optimization hub pull the rest of our sleep coverage together.
Insomnia that lasts more than a few weeks, loud snoring with pauses in breathing, falling asleep while driving, or low mood with sleep problems should be evaluated by a clinician. Supplements can mask a problem that needs treatment.
Research-use-only peptides are not sold for human use and have no approved human dose. See our medical disclaimer.
Sources
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complement Med Ther 2021;21(1):125, doi:10.1186/s12906-021-03297-z (abstract record).
- Yamadera W et al. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms 2007;5:126–131 (Springer).
- Sateia MJ et al. Clinical practice guideline for the pharmacologic treatment of chronic insomnia in adults: an AASM clinical practice guideline. J Clin Sleep Med 2017;13(2):307–349 (AASM guideline at a glance).
Frequently Asked
There is no good evidence that it is. DSIP's human data come from small, mostly older studies with inconsistent results, and it is a research-use-only peptide that is not FDA-approved. Melatonin has far more research, although the AASM suggests against using it for chronic insomnia.
A 2021 meta-analysis of three small trials in older adults found sleep onset about 17 minutes faster with magnesium than placebo, but rated the evidence low to very low quality. Total sleep time was not significantly different.
A 2007 study in people with unsatisfactory sleep found that 3 grams of glycine before bed improved subjective sleep quality and shortened the time to sleep onset and to slow-wave sleep on polysomnography. It was a small study that has not been confirmed in large trials or athletes.
The 2017 AASM guideline gives a weak recommendation that clinicians not use melatonin, diphenhydramine, L-tryptophan or valerian for sleep onset or maintenance insomnia, because the panel did not find the benefits large enough. It is not a statement that melatonin is dangerous.
Fix timing, caffeine and training load first, and get screened for sleep apnea if you snore loudly or wake unrefreshed. For chronic insomnia, cognitive behavioral therapy for insomnia is the standard first-line treatment.