YU Sleep ReviewsIndependent Research & Buyer GuidesWhat it is
Red tart (sour) cherries, Prunus cerasus, are one of the few foods that contain measurable melatonin alongside antioxidant compounds like proanthocyanidins. Concentrating the juice packages both into a small volume — which is exactly why a liquid sleep formula would put it first.
What the research used
The cited human work is small but pointed. Howatson and colleagues gave tart cherry juice concentrate and reported raised urinary melatonin alongside improved sleep quality and duration versus placebo. A pilot in older adults with insomnia also reported better sleep. Doses in these studies were substantial — think concentrated juice taken twice daily, not a garnish. Effect sizes were modest; this is a nudge, not a switch.
Evidence strength: modest, small-study
Two positive trials with small samples earn "modest, needs replication" — meaningful in a category where many ingredients have less, insufficient for confident dosing claims.
Inside YU Sleep
Listed first in the 637 mg blend, tart cherry concentrate is plausibly the largest single component — good news for formula coherence, since it's the ingredient with the friendliest safety profile at food-scale doses. The unanswered question is quantity: whether the concentrate amount approaches trial territory or sits at flavor-and-trace level. The label can't say, and neither can we.
Practical read
Tart cherry gives the formula a legitimate timing-lane anchor and its cherry flavor story. Buyers who want the ingredient at trial scale can also drink the juice itself — an inexpensive parallel experiment, just mind the sugar late in the evening, which is its own sleep disruptor per our bedtime snacks article.