If you've ever stood in a supplement aisle staring at 40 different sleep formulas, you know the problem. Every bottle promises deep, restorative sleep. Most don't deliver.
The supplement industry loves combining 12 ingredients at tiny doses and calling it a "sleep complex." But when you look at the actual research, only a handful of compounds have meaningful evidence behind them—and dosage matters enormously.
Here's what the data supports, ranked by evidence strength.
Melatonin isn't a sedative. It's a hormone your brain naturally produces when it gets dark, signaling to your body that it's time for sleep. Supplemental melatonin works best for two things: falling asleep faster and adjusting your circadian rhythm (jet lag, shift work, delayed sleep phase).
A 2013 meta-analysis in PLOS ONE analyzed 19 randomized controlled trials with 1,683 participants. Melatonin reduced sleep onset latency by an average of 7 minutes and increased total sleep time by about 8 minutes. That might not sound dramatic, but for people lying awake for 45+ minutes, shaving off a quarter of that is significant.
Here's where most people go wrong. Walk into any pharmacy and you'll find melatonin at 5mg, 10mg, even 20mg. These are massive doses.
Your body produces roughly 0.1-0.3mg of melatonin naturally. Research from MIT found that 0.3mg was sufficient to restore sleep in older adults with insomnia. A 2001 study showed that 0.5mg was as effective as 3mg for improving sleep quality.
Higher doses can actually backfire. At 5-10mg, melatonin can cause next-day drowsiness, vivid dreams or nightmares, and desensitize your melatonin receptors over time. More isn't better here.
| Dose | Evidence | Best For |
|---|---|---|
| 0.3-0.5mg | Strong | General sleep onset, long-term use |
| 1-3mg | Strong | Jet lag, circadian disruption |
| 5-10mg | Weak benefit over lower doses | Generally unnecessary |
Take it 30-60 minutes before bed. And buy a low-dose version—you can always take more, but cutting a 10mg tablet into precise fractions isn't practical.
Magnesium plays a role in over 300 enzymatic reactions in your body, including the activation of the parasympathetic nervous system—the "rest and digest" system. About 50% of Americans don't get enough magnesium from diet alone, according to USDA data.
The glycinate form is chelated (bonded to glycine, an amino acid that itself has calming properties). This makes it gentler on the stomach than magnesium citrate and better absorbed than magnesium oxide.
A 2012 double-blind RCT in the Journal of Research in Medical Sciences gave elderly subjects with insomnia 500mg of magnesium or placebo for 8 weeks. The magnesium group saw significant improvements in sleep time, sleep efficiency, melatonin concentration, and cortisol levels.
A 2021 systematic review of 3 RCTs found that magnesium supplementation significantly improved subjective measures of insomnia, particularly in older adults and those with low baseline magnesium.
Dosage: 200-400mg of elemental magnesium (as glycinate), taken 1-2 hours before bed. Start at 200mg. The tolerable upper intake level from supplements is 350mg/day per the NIH.
L-theanine is an amino acid found naturally in green tea. It doesn't knock you out. Instead, it promotes alpha brain wave activity—the same pattern seen during meditation and relaxed wakefulness. Think of it as turning down the mental noise.
A 2019 randomized controlled trial published in Nutrients gave 30 healthy adults either 200mg of L-theanine or placebo daily for 4 weeks. The L-theanine group reported reduced sleep latency, fewer sleep disturbances, and less use of sleep medication.
Another study on boys with ADHD (ages 8-12) found that 400mg of L-theanine daily improved sleep quality and sleep efficiency measured by actigraphy—not just self-reported data.
L-theanine is particularly interesting because it works well with caffeine during the day (smoothing out the jitteriness) and on its own for sleep at night. It has an excellent safety profile with no known dependency or tolerance issues.
Dosage: 100-400mg, 30-60 minutes before bed. Most studies use 200mg.
Valerian has been used for sleep since ancient Greece. It smells terrible—honestly, like old socks—but that's beside the point.
The evidence here is genuinely mixed. A 2006 meta-analysis in the American Journal of Medicine reviewed 16 studies and concluded that valerian "might" improve sleep quality but that the evidence was not compelling enough for a strong recommendation. Study quality was a major limitation.
A 2020 meta-analysis in the Journal of Evidence-Based Integrative Medicine was slightly more positive, finding that valerian improved sleep quality based on self-reported measures. But objective measures (polysomnography, actigraphy) didn't show significant differences.
Here's the thing about valerian: many people report that it works, but it seems to take 2-4 weeks of consistent use to notice effects. If you try it once and feel nothing, that's expected.
Dosage: 300-600mg of valerian root extract, taken 30 minutes to 2 hours before bed. Studies typically use standardized extracts with 0.8% valerenic acid.
Ashwagandha (Withania somnifera) is primarily known as an adaptogen for stress, but the "somnifera" in its name literally means "sleep-inducing." Recent studies suggest it might deserve that name.
A 2019 double-blind RCT in Cureus gave 150 healthy subjects either 120mg of ashwagandha extract (standardized to withanolides) or placebo. The ashwagandha group showed improvements in sleep onset latency, sleep quality, and total sleep time, with the strongest effects in participants who had insomnia at baseline.
A 2020 systematic review of 5 RCTs involving 400+ participants found that ashwagandha improved overall sleep quality, reduced anxiety, and improved mental alertness upon waking.
The mechanism likely involves GABAergic activity and cortisol reduction rather than direct sedation.
Dosage: 300-600mg of root extract (KSM-66 or Sensoril), taken before bed. More detail in our ashwagandha deep dive.
3g of glycine taken before bed reduced subjective sleepiness and improved next-day cognitive performance in a small 2006 Japanese study. It's cheap, safe, and a reasonable option, but the evidence base is small—just a few studies.
GABA is your brain's primary inhibitory neurotransmitter. Logically, more GABA should mean more calm. The problem: oral GABA doesn't cross the blood-brain barrier efficiently. Some studies show subjective relaxation effects, but it's unclear whether this is a central (brain) effect or peripheral. The evidence isn't strong enough for a recommendation.
Tryptophan is a precursor to serotonin, which converts to melatonin. The logic is sound, but taking melatonin directly is simpler and better studied. 5-HTP has some evidence for improving sleep quality at 100-300mg, but it can interact with SSRIs and other serotonergic medications. Use caution.
A common and reasonably evidence-supported stack:
Don't combine valerian with prescription sleep medications or benzodiazepines without medical supervision. There's a theoretical risk of excessive sedation.
A few things that sound good but lack evidence:
No supplement replaces sleep hygiene. If your room isn't dark, you're on your phone until midnight, and your schedule is erratic, no pill will fix that. Supplements work at the margins. — Suppi Research Team
| Supplement | Evidence | Dose | Best For |
|---|---|---|---|
| Melatonin | Strong | 0.3-3mg | Falling asleep, jet lag |
| Magnesium glycinate | Moderate-Strong | 200-400mg | Sleep quality, relaxation |
| L-Theanine | Moderate | 200mg | Racing thoughts, anxiety-related insomnia |
| Valerian root | Mixed | 300-600mg | General insomnia (needs 2-4 weeks) |
| Ashwagandha | Emerging | 300-600mg | Stress-related sleep issues |
| Glycine | Limited | 3g | Sleep quality, next-day alertness |
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