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Which Sleep Supplements Have Evidence Behind Them? A UK Guide
The sleep supplements with evidence behind them have it in minutes, not hours. Melatonin, a prescription-only medicine in the UK, brings sleep about 7 minutes sooner across 19 trials; magnesium about 17 minutes sooner in three small trials of older adults, low-quality evidence; ashwagandha about 5 minutes sooner with 4 points more sleep efficiency in one 60-person insomnia trial; glycine at 3 g, less next-day fatigue; L-theanine at 200 mg, a small gain in subjective sleep quality; valerian, more people saying "improved" with no measured change; tart cherry, three crossover trials of 20, 15 and 8 people.1, 2, 3, 4, 5, 6, 7 None of those ingredients carries an authorised sleep claim in Great Britain. Part of the Wellgard ashwagandha guide.
Do any sleep supplements actually work?
Several do something measurable: minutes of sleep onset, a few points of sleep efficiency or a lower insomnia score. No trial here supports "knocks you out" or "sleep through the night". That also explains the wording column: a health claim is authorised in Great Britain only when cause and effect are established to the regulator's standard, and no food ingredient has one for sleep, which is why a product may say that magnesium contributes to normal psychological function but not "helps you sleep".8 An absent claim is a statement about the register, not proof of no effect.
Which sleep supplements have evidence behind them? Ingredient by ingredient
| Ingredient | What the trials found | Trial dose and duration | What it may say on a UK label |
|---|---|---|---|
| Ashwagandha root extract | 60 people with insomnia: sleep onset 29.0 against 33.9 minutes, sleep efficiency 83.5% against 79.7%, at 10 weeks.3 | 600 mg a day, 8 to 10 weeks | No authorised claim; not in pregnancy or with a thyroid condition or thyroid medicine (ashwagandha with levothyroxine). |
| Magnesium | About 17 minutes faster to fall asleep, total sleep unchanged, in three trials of 151 older adults; low to very low quality. Detail on does magnesium help you sleep.2 | 500 mg a day for 8 weeks | Authorised nutrient wording at 15% NRV or more: contributes to normal psychological function, normal functioning of the nervous system and the reduction of tiredness and fatigue. No sleep wording. |
| Tart (Montmorency) cherry | Three crossover trials of 20, 15 and 8 people: about 25 minutes more sleep in healthy adults; less time awake after sleep onset in older adults with insomnia; 84 minutes more by sleep-laboratory recording in 8 completers. Detail on do sour cherries help you sleep.7 | 30 mL concentrate twice daily for 7 days; 240 mL juice twice daily for 2 weeks | No authorised claim. |
| Glycine | Less daytime fatigue after three nights of sleep cut by a quarter; earlier sleep-quality trials are not PubMed-indexed.4 | 3 g before bed | No authorised claim. |
| L-theanine | Anxiety and sleep-questionnaire scores improved in 30 adults over 4 weeks; pooled subjective sleep quality SMD 0.43 across 18 trials.5 | 200 mg a day for 4 weeks | No authorised claim. |
| L-tryptophan | Shorter time awake after sleep onset; 1 g or more did better than under 1 g; other measures unchanged.9 | 1 g or more | No authorised claim. |
| Valerian | Relative risk of reporting improved sleep 1.37; time to fall asleep and sleep-quality scores unchanged.6 | Varied between trials | A traditional herbal registration medicine in the UK; no food claim. |
| Lavender (standardised oral oil) | Anxiety score 3.83 points lower than placebo over 10 weeks, sleep improving with it.10 | 80 mg a day, 6 to 10 weeks | A traditional herbal registration medicine, not a supplement ingredient. |
| Melatonin | Sleep onset 7 minutes sooner and total sleep 8 minutes longer across 19 trials of 1,683 people; no fading with use.1 | Licensed tablet, usually up to 13 weeks (NHS) | Prescription-only medicine; cannot be a food ingredient. See why melatonin is prescription-only in the UK. |
What is the strongest natural sleep aid?
By the numbers above, the measured effects are minutes: melatonin, a medicine with the largest evidence base, about 7 across 19 trials; magnesium about 17 in 151 older adults; ashwagandha about 5 in 60 people. "Strongest" usually means sedation, and the sedating options, pharmacy sleep aids containing an antihistamine, are medicines the NHS limits to one or two weeks; prescription sleeping tablets are now rarely given because of side effects and dependence, and the NHS's first-line treatment is cognitive behavioural therapy for insomnia; see a GP if sleep-habit changes have not helped.11 The useful question is which outcome matches your problem: falling asleep (ashwagandha, magnesium, melatonin through a GP), staying asleep (tryptophan at 1 g or more), or feeling less wrecked the next day (glycine).
What can you drink before bed, and what is actually in it?
A drink carries the wording of what it contains, so the comparison is the dose in the cup against the dose in the trial. Chamomile tea steeps a gram or two of dried flower, while the one extract trial in chronic insomnia, 34 adults taking 270 mg of extract twice daily for 28 days, recorded small to moderate, non-significant effect sizes for sleep latency, night-time waking and daytime fatigue against placebo.12 Warm milk supplies well under a gram of tryptophan, where the pooled analysis favoured 1 g or more.9 A home-made cherry-and-magnesium "sleep cocktail" delivers whatever the spoon measures; the cherry trials used 30 mL of concentrate twice a day and the magnesium trials about 500 mg.2, 7 What not to eat or drink is clearer: the NHS says no big meal late and no tea, coffee or alcohol within six hours of bed.11
Sleep powders and sachets typically combine several of the ingredients above: glycine, magnesium, L-tryptophan, L-theanine, Montmorency cherry extract and botanicals such as lemon balm, chamomile and ashwagandha, melatonin-free because melatonin is prescription-only in the UK. Set each line of the label against the trial doses on this page: glycine at 3 g and theanine at 200 mg match the trials, tryptophan is usually well below the 1 g the pooled analysis favoured, and ashwagandha a fraction of the 600 mg sleep-trial dose. The wording a blend may carry is magnesium's: magnesium contributes to normal psychological function, to normal functioning of the nervous system and to the reduction of tiredness and fatigue. Label cautions apply to anyone on sedatives or antidepressants and in pregnancy.
How do you read a magnesium label? Elemental against compound
"1,000 mg of magnesium glycinate" and "375 mg of magnesium" are different kinds of number: the first is the weight of the whole compound, the second the elemental magnesium, and only the elemental figure compares with the 375 mg NRV or the 400 mg a day from supplements that the NHS calls unlikely to cause harm.11
| Product | Label figure | Elemental magnesium | Share of the 375 mg NRV |
|---|---|---|---|
| A label reading "375 mg magnesium" | 375 mg magnesium, the elemental figure stated | 375 mg | 100% |
| A label reading "1,000 mg magnesium glycinate" | 1,000 mg of the compound; glycinate is roughly 14% magnesium | about 140 mg | about 37% |
Both carry the same authorised magnesium wording and neither a sleep claim; which magnesium is best compares the forms.
What about waking at 4am in perimenopause?
None of the trials in the table tested early-morning waking, which is what the menopause threads describe. The evidence for that pattern sits with cognitive behavioural therapy for insomnia and with light and timing: morning daylight, a fixed getting-up time, no lying in after a bad night.11 HRT is the most effective treatment for menopausal sleep disturbance and sedating antihistamines carry the NHS one-to-two-week limit; both are GP conversations. Which menopause supplements have evidence reviews the rest.
What vitamin or mineral are you lacking if you can't sleep?
Usually none, with magnesium status the exception worth asking about, since its trials were clearest in people who started low. No vitamin deficiency causes insomnia as such; the NHS list of causes is stress, low mood, noise, heat, caffeine, alcohol, pain, an overactive thyroid and the menopause.11 Two blood tests are worth asking a GP about: ferritin, because low iron drives restless legs, and thyroid function. The signs of low magnesium sets out what running short looks like.2
Frequently asked questions
Is there a sleep supplement that actually works?
Magnesium (17 minutes, older adults, low quality), ashwagandha (5 minutes and 4 points in 60 people) and glycine (less next-day fatigue at 3 g) have placebo-controlled results; none has a GB sleep claim.2, 3, 4
What is the safest sleep aid for seniors?
The licensed route is melatonin through a GP, which the NHS prescribes mainly from age 55; magnesium's trials were in older adults at about 500 mg a day, above the 400 mg a day from supplements the NHS calls unlikely to cause harm; a supplement stays at its label dose.1, 2, 11
Are there melatonin-free sleep gummies or powders?
Every sleep product legally on a UK shelf is melatonin-free, because melatonin is a medicine; the table above shows what else is in them, and at what dose.
What is the best sleep aid for adults with anxiety?
For a diagnosed anxiety disorder the GP and NHS talking therapies come first; among the ingredients here, the anxiety trials belong to L-theanine, oral lavender oil (a registered herbal medicine) and ashwagandha, each small.5, 10
Sources
- Ferracioli-Oda E, Qawasmi A, Bloch MH. Meta-analysis: melatonin for the treatment of primary sleep disorders. PLoS One, 2013. PubMed 23691095.
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies, 2021. PubMed 33865376.
- Langade D, et al. Efficacy and safety of ashwagandha root extract in insomnia and anxiety: a double-blind, randomized, placebo-controlled study. Cureus, 2019. PubMed 31728244.
- Bannai M, et al. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology, 2012. PubMed 22529837.
- Hidese S, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults. Nutrients, 2019. PubMed 31623400; Bulman A, et al. The effects of L-theanine consumption on sleep outcomes: a systematic review and meta-analysis. Sleep Medicine Reviews, 2025. PubMed 40056718.
- Fernández-San-Martín MI, et al. Effectiveness of valerian on insomnia: a meta-analysis of randomized placebo-controlled trials. Sleep Medicine, 2010. PubMed 20347389.
- Howatson G, et al. Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. European Journal of Nutrition, 2012. PubMed 22038497; Pigeon WR, et al. Journal of Medicinal Food, 2010. PubMed 20438325; Losso JN, et al. American Journal of Therapeutics, 2018. PubMed 28901958.
- Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. gov.uk.
- Sutanto CN, Loh WW, Kim JE. The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutrition Reviews, 2022. PubMed 33942088.
- Möller HJ, et al. Efficacy of Silexan in subthreshold anxiety: meta-analysis of randomised, placebo-controlled trials. European Archives of Psychiatry and Clinical Neuroscience, 2019. PubMed 29150713.
- NHS. Insomnia. nhs.uk/conditions/insomnia; NHS. Vitamins and minerals: others (magnesium). nhs.uk/conditions/vitamins-and-minerals/others.
- Zick SM, et al. Preliminary examination of the efficacy and safety of a standardized chamomile extract for chronic primary insomnia. BMC Complementary and Alternative Medicine, 2011. PubMed 21939549.
