Sleepy girl mocktail

What the evidence shows

The drink spread on TikTok in 2023: tart cherry juice, a scoop of magnesium powder, and prebiotic soda or sparkling water on top. Nobody has studied it as a drink. What can be checked is the evidence for its two active ingredients, and there is not much of it.

Tart cherry juice. Montmorency tart cherries contain small amounts of melatonin, the hormone that helps time sleep, which is why they come up in sleep research. Three small trials are usually quoted.

• In a UK study of 20 healthy adults, a week of tart cherry juice concentrate raised melatonin levels and increased time asleep, measured by wrist monitor, compared with a placebo drink.
• In a US pilot with 15 older adults who had insomnia, a tart cherry juice blend cut the time spent awake during the night compared with a placebo, but did not help them fall asleep faster or sleep longer overall. The authors described the effects as modest, and well below those of proven insomnia treatments.
• In a second US pilot, the eight older adults with insomnia who completed the study slept longer while drinking cherry juice, measured overnight in a sleep laboratory.

These results are encouraging, but the studies are tiny and short, and none of them tested the mocktail. Two of the three used older adults with insomnia, so they say little about a healthy person in their twenties having a restless week.

Magnesium. A 2021 review gathered the randomised trials of magnesium supplements for insomnia in older adults. It found three, with 151 people in total. Taken together, people on magnesium fell asleep about 17 minutes sooner than on a placebo, and the extra time asleep was too small to be sure of. All three trials were at moderate to high risk of bias, and the reviewers rated the quality of the evidence low to very low.

The prebiotic soda or sparkling water is there for taste. It is not part of the sleep claim.

So the verdict is unproven. Each ingredient has a little early evidence, mostly in older adults with insomnia, and the drink as a whole has none. It is also unlikely to do any harm at sensible amounts.

Who it might suit

If you like the taste and it becomes a calm part of your evening, there is little reason not to have it. Part of its appeal may simply be the ritual: something slow and pleasant to do at the same time each night, away from a screen.

Older adults have the most reason to try the ingredients, since that is who most of the research involved. Even so, the effects found were modest, so judge it over a couple of weeks rather than a single night.

It is unlikely to help if something else is keeping you awake, such as pain, a body clock that has drifted late, or worry. For a mind that won’t settle, a technique aimed at the thoughts themselves is a better place to start.

What to watch for

The magnesium dose. Powders vary a lot in how much magnesium a scoop gives. The NHS says 400mg or less a day from supplements is unlikely to cause harm, and that higher doses can cause diarrhoea, which is the last thing you want in the middle of the night. Check the label for the amount of magnesium per serving, not the weight of the powder.

Other medicines. If you take regular medication or have a long-term condition, ask a pharmacist before adding a magnesium supplement.

Sugar. Tart cherry juice is still fruit juice. If that matters to you, check the label, and keep the serving small.

Something else going on. In one of the cherry juice studies, some of the volunteers turned out to have sleep apnoea, which needs quite different treatment. If you snore loudly, wake gasping, or feel exhausted however long you sleep, see a doctor rather than trying a drink.

Common questions

Does tart cherry juice contain melatonin?

Yes, in small amounts. In the UK study, melatonin levels rose in people who drank the concentrate for a week. Researchers have also looked at other compounds in the fruit that may play a part.

Which magnesium is best for sleep?

The trials so far don’t show that one form works better than another. Magnesium glycinate is the form the trend recommends, but the research doesn’t settle the question.

Is it safe to drink every night?

For most healthy adults, at sensible amounts, probably yes. Keep the magnesium within the NHS guide of 400mg a day from supplements, and ask a pharmacist first if you take other medicines.