Inside the Z-z-Zen sleep formula: what melatonin, saffron, L-glycine and L-theanine each do

Last updated: 2026-10

A Z-z-Zen strip contains 1 mg of melatonin, the exact amount the EU attaches to its authorised claim on falling asleep, and 14 mg of saffron extract, a dose that has been studied for sleep quality in adults. L-glycine and L-theanine, 12 mg each, complete the formula, which leaves melatonin as the smallest of its four ingredients by weight.

Smart Strips chose that order on purpose. Z-z-Zen was designed for a particular kind of night: sleep comes without much of a fight at eleven, and by four the mind is awake and already rehearsing the day. Below, the formula is taken apart one ingredient at a time: the amount, what research has measured, and where that research stops short of our product.

What exactly is in one Z-z-Zen strip?

Four active ingredients, 39 mg in total, on a thin pullulan film that dissolves on the tongue in 7 to 30 seconds. Listed by weight:

Only melatonin has an authorised health claim in the EU. For the other three, the third column says what research has looked at, and nothing more.

Why is melatonin not the lead ingredient?

Because the night Z-z-Zen was built for is longer than the first half hour in bed, and melatonin's authorised role in the EU concerns the time it takes to fall asleep. The product was designed for more of the night: falling asleep more easily, then staying asleep through the hours when sleep turns lighter.

Melatonin's own profile points the same way. A systematic review of its pharmacokinetics puts the time to peak at about 50 minutes after an immediate-release oral dose and the half-life at about 45 minutes (Harpsøe et al., 2015). It arrives around bedtime and is cleared within hours. Melatonin sits at the amount the EU claim names, and the remaining 38 mg of the strip goes to ingredients our formulators chose with the rest of the night in mind.

What does 1 mg of melatonin do?

In the EU, one thing can be said about it, in these exact words: "Melatonin contributes to the reduction of time taken to fall asleep. The beneficial effect is obtained by consuming 1 mg of melatonin close to bedtime." Regulation (EU) No 432/2012 authorises the claim only for food that contains 1 mg of melatonin per portion. Every Z-z-Zen strip contains exactly that.

Why 1 mg, when shelves are full of 5 mg and 10 mg?

Small amounts of melatonin already register. In a controlled crossover study of 30 adults over 50, with doses taken 30 minutes before bedtime, 0.3 mg showed an effect on sleep (Zhdanova et al., 2001). That does not make larger amounts pointless. A 2024 dose-response meta-analysis of 26 randomised trials found that the time to fall asleep kept shortening as the dose rose, up to 4 mg a day (Cruz-Sanabria et al., 2024).

The 1 mg in Z-z-Zen is therefore not a statement that higher doses fail. It is the amount the European claim is written around, and it keeps melatonin in proportion inside a formula of four ingredients. Label accuracy and the sugar in gummies are a separate subject, covered in our comparison of melatonin strips vs melatonin gummies.

How much swallowed melatonin actually reaches the bloodstream?

A fraction. In 12 healthy adults, melatonin tablets of 2 mg and 4 mg showed an absolute bioavailability of approximately 15% (DeMuro et al., 2000), and the Harpsøe review reports a range of 9 to 33% for oral melatonin.

The lining of the mouth offers part of the dose a different route. A systematic review of alternative routes concluded that "oral transmucosal administration of melatonin exhibited a high plasma concentration compared to oral administration" (Zetner et al., 2016). In a crossover study in 13 healthy men, a 1 mg sublingual melatonin spray reached peak blood levels in 23.3 minutes on average, against 64.2 minutes for a 1.9 mg prolonged-release tablet (Ait Abdellah et al., 2023). Two caveats belong beside those figures: the tablet was designed to release slowly, and the study was sponsored by the company that makes both products. It shows what the route can do. It is not a measurement of Z-z-Zen.

With an oral dissolvable strip, part of the dose is absorbed through the lining of the mouth, and that part avoids first-pass liver metabolism. The rest is swallowed with saliva and follows the usual digestive path. For the strip format compared with a tablet, Smart Strips uses three figures together: up to 95% bioavailability, up to 4x faster absorption and up to 30% higher effectiveness. The principle behind all of this is explained in what bioavailability means for supplements.

What does saffron do for sleep?

Saffron extract has been studied for sleep quality in adults, and 14 mg is a dose that was tested directly. In a randomised, double-blind, placebo-controlled study, 120 adults with poor sleep took placebo, 14 mg or 28 mg of a standardised saffron extract one hour before bed for 28 days. The authors reported that "sleep improvements were similar for the two administered saffron doses" (Lopresti et al., 2021). A separate six-week randomised trial used 15.5 mg a day of a different saffron extract and reported better overall sleep quality scores (Pachikian et al., 2021).

The 2021 study also found that saffron raised evening melatonin and left evening cortisol unchanged, while several other questionnaire and sleep diary measures showed no significant difference from placebo. The findings belong to the specific extracts tested and are not a promise for any strip, ours included.

That evidence is why saffron is the largest ingredient in Z-z-Zen. Among the three ingredients without an authorised claim, it is the only one present at an amount research has tested for sleep.

Why are L-glycine and L-theanine in the formula?

They are supporting parts of the formula. Both amino acids have been studied in relation to sleep, at amounts far larger than a strip can carry.

L-glycine was studied at 3 g before bedtime in people with chronically poor sleep, where it shortened the time to fall asleep measured in a sleep laboratory (Yamadera et al., 2007). The 12 mg in Z-z-Zen is 250 times less. L-theanine, the amino acid found in tea leaves, was taken at 200 mg a day by 30 healthy adults in a four-week placebo-controlled crossover trial that included a sleep quality questionnaire (Hidese et al., 2019). Our 12 mg is roughly one sixteenth of that. Neither amino acid has an authorised health claim in the EU.

We do not present those studies as evidence for our strip. A strip carries milligrams, not grams, and the four-ingredient combination has not itself been tested in a clinical study. L-glycine and L-theanine were included with the later part of the night in mind, next to melatonin and saffron, which carry the evidence. During the day L-theanine appears with caffeine in FOCUS, a pairing covered in focus without jitters, and with GABA and saffron in ANXIETY.

Why does a sleep formula think about 4am?

Because sleep is not equally deep all night. You cycle through non-REM and REM sleep several times; deep sleep comes in longer periods during the first half of the night, and REM periods grow longer towards morning (NINDS). Once you are awake, the body is already turning towards the day: cortisol typically rises by 38 to 75% after waking and peaks about 30 minutes later (Elder et al., 2014).

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults sleep seven or more hours per night on a regular basis (Watson et al., 2015). Asleep at eleven and awake at four comes to five. That shortfall is the reason Z-z-Zen was designed around the whole night rather than its first minutes. The habits that protect those early hours, from morning light to evening alcohol, are in our guide to why you wake up at 4am.

When should you take Z-z-Zen?

20 to 30 minutes before sleep, as the label says. That window fits the EU condition of 1 mg "close to bedtime", and it spans the timings used in the studies above: melatonin 30 minutes before bedtime in Zhdanova's study, saffron one hour before bed in Lopresti's.

Place the strip on your tongue with dry fingers and let it dissolve, which takes 7 to 30 seconds. No water is needed, so it fits after brushing your teeth. For the logic of timing across the whole day, see when to take supplements.

Who should not take Z-z-Zen?

Z-z-Zen is formulated for adults. Melatonin in pregnancy has not been well studied: according to MotherToBaby, it is not known whether taking melatonin would increase the chance of birth defects, and the safety of supplements during breastfeeding has not been well studied either.

If you are pregnant, nursing, taking medication or have a medical condition, consult your doctor before using any supplement. If poor sleep continues for several weeks, a doctor is the right next step. Do not exceed the recommended daily intake on the pack.

The most useful test takes a fortnight: one strip 20 to 30 minutes before the lights go out, and a line in a notebook each morning about the time you woke. Discover Z-z-Zen or explore the full range.

FAQ

Is melatonin the main ingredient in Z-z-Zen?

No. Melatonin is 1 mg of the 39 mg of active ingredients in each strip. Saffron extract, at 14 mg, is the largest, followed by L-glycine and L-theanine at 12 mg each.

How much melatonin is in Z-z-Zen?

1 mg per strip. Melatonin contributes to the reduction of time taken to fall asleep. The beneficial effect is obtained by consuming 1 mg of melatonin close to bedtime.

Is 1 mg of melatonin a low dose?

It is the amount named in the EU authorised claim. A dose of 0.3 mg already showed an effect in adults over 50 (Zhdanova 2001), and a 2024 meta-analysis found effects growing with dose up to 4 mg a day.

What dose of saffron has been studied for sleep?

A 120-person study found similar sleep improvements at 14 mg and 28 mg of a standardised extract taken one hour before bed (Lopresti 2021). Another trial used 15.5 mg a day (Pachikian 2021).

Has research tested L-glycine and L-theanine at 12 mg?

No. Sleep studies used L-glycine at 3 g and L-theanine at 200 mg a day. In Z-z-Zen both are supporting ingredients, and neither has an authorised health claim in the EU.

When should I take Z-z-Zen?

20 to 30 minutes before sleep. The strip dissolves on the tongue in 7 to 30 seconds, without water.

Sources

1. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, Annex (melatonin entries). https://www.legislation.gov.uk/eur/2012/432/annex
2. DeMuro RL, Nafziger AN, Blask DE, Menhinick AM, Bertino JS. The absolute bioavailability of oral melatonin. J Clin Pharmacol. 2000;40(7):781-784. https://doi.org/10.1177/00912700022009422
3. Harpsøe NG, Andersen LPH, Gögenur I, Rosenberg J. Clinical pharmacokinetics of melatonin: a systematic review. Eur J Clin Pharmacol. 2015;71(8):901-909. https://doi.org/10.1007/s00228-015-1873-4
4. Zhdanova IV, Wurtman RJ, Regan MM, Taylor JA, Shi JP, Leclair OU. Melatonin treatment for age-related insomnia. J Clin Endocrinol Metab. 2001;86(10):4727-4730.
5. Cruz-Sanabria F, Bruno S, Crippa A, Frumento P, Scarselli M, Skene DJ, Faraguna U. Optimizing the time and dose of melatonin as a sleep-promoting drug: a systematic review of randomized controlled trials and dose-response meta-analysis. J Pineal Res. 2024;76(5):e12985. https://doi.org/10.1111/jpi.12985
6. Zetner D, Andersen LPH, Rosenberg J. Pharmacokinetics of alternative administration routes of melatonin: a systematic review. Drug Res (Stuttg). 2016;66(4):169-173. https://doi.org/10.1055/s-0035-1565083
7. Ait Abdellah S, Raverot V, Gal C, Guinobert I, Bardot V, Blondeau C, Claustrat B. Bioavailability of melatonin after administration of an oral prolonged-release tablet and an immediate-release sublingual spray in healthy male volunteers. Drugs R D. 2023;23(3):257-265. https://doi.org/10.1007/s40268-023-00431-9
8. Lopresti AL, Smith SJ, Drummond PD. An investigation into an evening intake of a saffron extract (affron) on sleep quality, cortisol, and melatonin concentrations in adults with poor sleep: a randomised, double-blind, placebo-controlled, multi-dose study. Sleep Med. 2021;86:7-18. https://doi.org/10.1016/j.sleep.2021.08.001
9. Pachikian BD, Copine S, Suchareau M, Deldicque L. Effects of saffron extract on sleep quality: a randomized double-blind controlled clinical trial. Nutrients. 2021;13(5):1473. https://doi.org/10.3390/nu13051473
10. Yamadera W, Inagawa K, Chiba S, et al. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms. 2007;5:126-131. https://doi.org/10.1111/j.1479-8425.2007.00262.x
11. Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, Kunugi H. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362. https://doi.org/10.3390/nu11102362
12. National Institute of Neurological Disorders and Stroke. Brain Basics: Understanding Sleep. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep
13. Elder GJ, Wetherell MA, Barclay NL, Ellis JG. The cortisol awakening response: applications and implications for sleep medicine. Sleep Med Rev. 2014;18(3):215-224. https://doi.org/10.1016/j.smrv.2013.05.001
14. Watson NF, Badr MS, Belenky G, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. J Clin Sleep Med. 2015;11(6):591-592. https://doi.org/10.5664/jcsm.4758
15. MotherToBaby. Melatonin. Fact sheet, NCBI Bookshelf NBK583263. https://www.ncbi.nlm.nih.gov/books/NBK583263/