Nutrifact Guide · Last updated October 2026 · Educational information only, not medical advice

Searches for sleep and stress supplements keep climbing. Magnesium, ashwagandha, L-theanine, glycine, apigenin and melatonin all promise calmer evenings and deeper sleep. But what do the studies actually show?

This guide looks at each ingredient in plain language: what the research found, what is still unclear, and what to watch out for. The short version is that most of the evidence comes from small, short trials. The effects are usually modest, and none of these products replaces medical care for insomnia, anxiety or depression.

At a glance

• Magnesium: mixed evidence for sleep. May shorten the time it takes to fall asleep in older adults, but the studies are low quality. Keep supplemental magnesium at or below 350 mg a day unless a clinician says otherwise.

• Ashwagandha: the best-supported option here for stress and anxiety, with small sleep gains. Rare cases of liver injury have been reported.

• L-theanine: 200–400 mg a day was linked to lower stress in people facing stressful situations. Sleep benefits are mostly self-reported.

• Glycine: about 3 g before bed improved how people rated their sleep in small, short studies.

• Apigenin: the human evidence comes mainly from chamomile extract, not from pure apigenin capsules.

• Melatonin: a body-clock signal, not a sedative. Fine for short-term use for most people, but product labels are often inaccurate.

Magnesium for sleep and stress

Magnesium is an essential mineral, and it is the most searched ingredient on this list. Observational studies link better magnesium status with better sleep. A systematic review of nine studies with 7,582 people found that link in observational data, but the randomized trials gave conflicting results about whether taking a supplement actually helps.

A meta-analysis in older adults with insomnia pooled three randomized trials with 151 people. Those taking magnesium fell asleep about 17 minutes sooner than those on placebo. Total sleep time rose by about 16 minutes, but that gain was not statistically significant. The authors rated the evidence as low to very low quality, with moderate-to-high risk of bias in every trial. One of the trials used 500 mg of magnesium for eight weeks in older adults, according to a summary of the review. That dose is above the supplemental upper limit discussed below.

Magnesium glycinate

Magnesium glycinate is popular because the mineral is bound to glycine, an amino acid that also appears in sleep research (see the glycine section). We did not find head-to-head trials showing that glycinate works better for sleep than other forms, so treat strong claims about one form being the best with caution. Glycinate is also a fairly low-percentage source of the mineral. One dosage guide estimates it at about 14% elemental magnesium by weight, so a large capsule may contain much less magnesium than the number on the front suggests. Always check the “elemental magnesium” line on the Supplement Facts panel.

Magnesium L-threonate

Magnesium L-threonate (sold under the brand name Magtein) is marketed for brain health. A randomized, placebo-controlled trial published in Frontiers in Nutrition gave 2 g a day of the compound, or placebo, to 100 adults aged 18 to 45 who were unhappy with their sleep. After six weeks, the magnesium group scored better on an overall cognition measure. On sleep, the picture was mixed. People reported less sleep-related impairment, but there were no overall differences in sleep disturbances, restorative sleep or general wellbeing. Sleep measured with a wearable ring showed no group differences, so the authors described the benefit as subjective rather than objective. A news report on the trial covers the same findings.

Difference between Magnesium glycinate and magnesium L-threonate

Two points of context. This is one trial of one branded form, and the ingredient maker has promoted the results. The maker’s own press release also notes that the European Food Safety Authority has not approved health claims for magnesium L-threonate beyond standard nutrition claims.
Magnesium glycinate and magnesium L-threonate are both magnesium bound to a carrier, but they are sold for different goals. Glycinate pairs the mineral with glycine, an amino acid that has its own small sleep studies, and it is mainly chosen as a general-purpose form for relaxation and sleep support. It contains roughly 14% elemental magnesium by weight, so the elemental amount on the Supplement Facts panel matters more than the capsule size. L-threonate is a patented, branded form (Magtein) marketed for brain health and is reported to reach the brain. It is only about 7% elemental magnesium, so doses are large in weight, and the main randomized trial used 2 g a day of the compound for six weeks. That trial found better scores on a cognition measure and some self-reported sleep improvement, but no change in sleep measured by a wearable device. We found no head-to-head trials showing that either form works better for sleep, so the choice is mostly about what you want from it, how well you tolerate it and the cost, and total supplemental magnesium should stay at or below the NIH limit of 350 mg a day unless a clinician advises otherwise.

How much is safe?

The US National Institutes of Health sets an upper limit of 350 mg a day for magnesium from supplements and medications in adults. The limit does not apply to magnesium from food. Going over it can cause diarrhea and nausea. People with reduced kidney function face a higher risk of magnesium building up, as summarized from NIH guidance here, so they should speak to a clinician first.

Ashwagandha for stress, anxiety and sleep

Ashwagandha (Withania somnifera) is a root used in traditional Indian medicine. It has the strongest research record in this group for stress and anxiety.

The NIH Office of Dietary Supplements describes a 2021 review of seven studies with 491 adults, all from India, who took ashwagandha or placebo for six to eight weeks. Separately, the Merck Manual reports a meta-analysis of 12 randomized trials with 1,002 adults that found a statistically significant drop in anxiety and stress. It also reports small sleep improvements in a meta-analysis of capsule trials, especially when people took it for more than eight weeks.

Results are not uniform. The NIH page notes one trial in which ashwagandha did not lower perceived stress but did reduce fatigue. Most trials are small and short, so we do not yet know how it performs over years.

Safety: the liver warning

Ashwagandha is not risk-free. The NIH’s LiverTox database lists it as a likely cause of clinically apparent liver injury, although this is rare. Cases typically appeared two to twelve weeks after starting. Most were mild to moderate and cleared up, but a few were fatal or led to transplant, mostly in people with existing liver disease. LiverTox advises avoiding it in people with cirrhosis or advanced chronic liver disease. If you notice yellow skin or eyes or unusual itching while taking it, stop and get medical care promptly.

L-theanine for calm and sleep

L-theanine is an amino acid found mainly in tea. A systematic review of nine randomized trials concluded that 200–400 mg a day may reduce stress and anxiety in people exposed to stressful conditions. The authors called for longer and larger studies before it could be recommended as a treatment.

For sleep, a review of 19 randomized trials with 897 participants reported better self-rated sleep onset in 10 studies, less daytime dysfunction in nine and better overall sleep quality scores in 12. A recent mini-review adds that doses of 200–450 mg a day can support sleep quality with little effect on total sleep time, and that L-theanine is generally well tolerated. In short, it looks more like a gentle calming aid than a sleeping pill.

Glycine before bed

Glycine is the smallest amino acid, and you also get it from protein foods. In a Japanese study of volunteers with ongoing poor sleep, 3 g taken before bedtime improved subjective sleep quality and sleep efficiency. Sleep-lab recordings showed people fell asleep faster, and the normal pattern of sleep stages stayed unchanged. Participants also felt less sleepy the next day. A follow-up study in partially sleep-restricted volunteers examined daytime sleepiness and fatigue after short nights.

A later review summarizes these studies: 3 g taken 30 to 60 minutes before bed for a few days improved sleep quality and alertness in healthy people. The studies are small and short, so this is promising but early.

Apigenin: popular, but mostly tested through chamomile

Apigenin is a plant compound found in chamomile, parsley and celery. Lab work suggests it interacts weakly with the same brain receptors targeted by sedative drugs, which is why it became popular for sleep.

The human evidence is thinner than the marketing. The Merck Manual’s chamomile page describes a placebo-controlled trial of chamomile extract standardized to 1.2% apigenin in people with mild-to-moderate anxiety, which showed possible modest benefit. It adds that chamomile may improve sleep quality, but that few studies show consistent results. Independent reviews, such as this evidence summary and this report, make the same key point: the trials used whole chamomile extract, which contains many compounds, not pure apigenin. We cannot credit the results to apigenin alone. Those two sources are commercial sites, so treat them as secondary.

Chamomile can also interact with medicines. The Merck Manual notes that it may raise blood levels of cyclosporine, so check with a pharmacist if you take prescription drugs.

Melatonin and its alternatives

Melatonin is a hormone your body makes to signal night-time. It works best for timing problems, such as jet lag or a late body clock, and less well as an all-purpose sleep aid. The NIH’s National Center for Complementary and Integrative Health says short-term use appears safe for most people, while long-term safety information is lacking. The Mayo Clinic advises not driving or using machinery within five hours of taking it and warns that over-the-counter products vary widely in how much melatonin they contain. Common side effects include headache, dizziness, nausea and daytime drowsiness, and a sleep specialist quoted by Powers Health suggests 1–3 mg about an hour before bed.

The label problem

A 2023 JAMA research letter tested 25 melatonin gummy products. Twenty-two were inaccurately labeled, with actual amounts ranging from 74% to 347% of what the label claimed, and one contained CBD instead of melatonin, according to coverage of the study. The lead researcher said a USP verification mark makes inaccurate amounts much less likely, as reported by KHOU. The American Academy of Sleep Medicine has also urged parents to be careful with melatonin for children, as noted in the Powers Health article above.

Are the other ingredients real alternatives?

Magnesium, L-theanine, glycine, ashwagandha and chamomile are often sold as melatonin alternatives. They work differently: some calm the mind, others may ease the body into sleep. We found no head-to-head trials comparing them with melatonin, so none can be called better or safer. What they share is a need for patience, since several trials ran for six weeks or more.

How to approach these supplements sensibly

1. Start with sleep habits. A regular schedule, a dark and cool room and limiting caffeine late in the day come first. The Mayo Clinic also recommends not using melatonin as the first or only solution.

2. Try one ingredient at a time. Give it a few weeks and note your sleep and stress levels. Blends are popular, but the trials above tested single ingredients.

3. Check the label. Look for the elemental amount (for magnesium), a standardized extract (for ashwagandha and chamomile) and independent testing such as a USP mark.

4. Know who needs extra care. Check with a doctor or pharmacist first if you are pregnant or breastfeeding, have kidney or liver disease, or take prescription medicines.

5. Know when to get help. If poor sleep, anxiety or low mood lasts for weeks or affects daily life, see a healthcare professional. A supplement can mask a problem that needs proper treatment.

The bottom line

The science supports modest benefits, not miracles. Ashwagandha has the clearest data for stress, with a rare but serious liver warning. L-theanine and glycine show gentle, mostly self-reported gains. Magnesium is popular but the sleep trials are mixed and low in quality. Apigenin’s evidence comes largely from chamomile. Melatonin helps with timing but needs a trustworthy product. Pick based on your situation and safety, not on trends.

References

1. Magnesium and sleep health, systematic review: https://pubmed.ncbi.nlm.nih.gov/35184264/

2. Oral magnesium for insomnia in older adults, systematic review and meta-analysis (BMC Complement Med Ther, 2021): https://pubmed.ncbi.nlm.nih.gov/33865376/

3. Summary of the magnesium and sleep review (Examine): https://examine.com/research-feed/study/dZZXad

4. Magnesium L-threonate (Magtein) randomized trial, Frontiers in Nutrition, 2025: https://www.frontiersin.org/articles/10.3389/fnut.2025.1729164/full

5. NutraIngredients report on the threonate trial: https://www.nutraingredients.com/Article/2026/01/16/magtein-magnesium-l-threonate-may-boost-cognitive-performance-and-improve-sleep

6. Magtein press release (manufacturer): https://magtein.prezly.com/magteinr-associated-with-improvements-in-cognition-brain-age-and-physiological-stress-markers-clinical-trial-finds

7. NIH Office of Dietary Supplements, The Scoop (May 2024), magnesium upper limit: https://ods.od.nih.gov/pubs/The_Scoop_May_2024.pdf

8. Magnesium dosing and kidney function summary (Pillo): https://pillo.care/blog/is-500mg-of-magnesium-too-much

9. Magnesium elemental content by form (Verified Supplement Data): https://verifiedsupplementdata.com/magnesium/dosage-guide/

10. NIH Office of Dietary Supplements, Ashwagandha fact sheet: https://ods.od.nih.gov/factsheets/Ashwagandha/

11. Merck Manual, Ashwagandha: https://www.merckmanuals.com/professional/special-subjects/dietary-supplements/ashwagandha

12. NIH LiverTox, Ashwagandha: https://www.ncbi.nlm.nih.gov/books/NBK548536/

13. L-theanine, stress and anxiety, systematic review (Plant Foods for Human Nutrition, 2020): https://publications.aston.ac.uk/id/eprint/41068

14. L-theanine and sleep, review of 19 trials (NutraIngredients report): https://www.nutraingredients.com/Article/2025/03/31/review-explores-l-theanine-as-sleep-aid/

15. L-theanine, cognition, mood and sleep, mini-review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13587617/

16. Glycine and subjective sleep quality (Sleep and Biological Rhythms): https://link.springer.com/article/10.1111/j.1479-8425.2007.00262.x

17. Glycine in partially sleep-restricted volunteers (Frontiers in Neurology): https://www.frontiersin.org/articles/10.3389/fneur.2012.00061/pdf

18. Glycine review (NutraIngredients report): https://www.nutraingredients.com/Article/2023/11/08/glycine-supplementation-before-bedtime-improves-sleep-quality-and-alertness-says-new-review/

19. Merck Manual, Chamomile: https://www.merckmanuals.com/professional/special-subjects/dietary-supplements/chamomile

20. Apigenin evidence summary (Superpower, commercial): https://superpower.com/guides/apigenin-mechanism-sleep-evidence-review

21. Apigenin report (Outliyr, commercial): https://outliyr.com/reports/apigenin

22. NCCIH, Melatonin: what you need to know: https://www.nccih.nih.gov/health/melatonin-what-you-need-to-know

23. Mayo Clinic, Melatonin side effects: https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/melatonin-side-effects/faq-20057874

24. Powers Health, Should I take melatonin for sleep?: https://www.powershealth.org/about-us/newsroom/health-library/2023/04/03/should-i-take-melatonin-for-sleep-an-expert-has-answers

25. JAMA 2023 research letter on melatonin gummies: https://doi.org/10.1001/jama.2023.2296

26. NutraIngredients report on the JAMA gummy study: https://www.nutraingredients.com/Article/2023/04/26/Wake-up-call-or-false-alarm-New-JAMA-paper-reports-problems-with-melatonin-gummies

27. KHOU report on melatonin label accuracy and USP marks: https://khou.com/article/news/verify/medicine/melatonin-gummy-jama-study-mislabeled-doses-quantities-strengths-higher-than-labeled/536-61b8d1f9-0c43-4847-b916-0a0098d5174d

This article is for general education and is not a substitute for advice from a doctor or pharmacist. Supplements are not intended to diagnose, treat, cure or prevent any disease.