The research group – including experts from the United States (Nicholas Institute of Sports Medicine), the UK (Northumbria University and the University of Surrey) and South Africa (University of Johannesburg) – conducted a study of 20 healthy men and women with an average age of 27 years old.
Half of the group was randomly assigned to drink tart cherry juice concentrate and the other half drank a placebo for seven days. The juice concentrate was made from tart Montmorency cherries (Prunus cerasus).
The results determined that the cherry group slept an average of 34 minutes more per night and had a 5-6% increase in sleep efficiency. Sleep efficiency is the time spent asleep as a proportion of time in bed.
The melatonin levels among the cherry group increased significantly, while the placebo group did not have any melatonin increase. Within 48 hours of cherry juice consumption, the urine of the cherry drinkers showed increased levels of 6-sulfatoxymelatonin – the primary melatonin metabolite. The researchers also measured melatonin levels by studying the subjects’ circadian rhythms.
The researchers concluded that, “these data suggest that consumption of a tart cherry juice concentrate provides an increase in exogenous melatonin that is beneficial in improving sleep duration and quality in healthy men and women and might be of benefit in managing disturbed sleep.”
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“This is the first investigation to demonstrate that dietary tart cherry juice concentrate increases urinary melatonin levels and provides improved sleep time and quality in a healthy adult population,” the researchers stated in the European Journal of Nutrition.
Earlier research has confirmed that Montmorency cherries contain melatonin. Research led by Dr. Russel Reiter from the University of Texas Health Science Center in San Antonio, Texas determined that the tart cherries will contain up to contain up to 13.5 nanograms (ng) of melatonin per gram of cherries. This is typically more than the levels found in the bloodstream.
Another study, this from Spain’s University of Extremadura, also found that sleep quality and duration increased among elderly adults who consumed Jerte Valley cherries – another variety of tart cherries.
While cherries significantly spike melatonin levels and increase sleep quality, research on supplemental synthetic melatonin or melatonin extracted from the pineal glands of cows has been conflicting. These exogenous forms have been shown to improve sleep-phase disorders, but sleep quality results have been equivocal.
The difference may well lie in cherries’ phytochemical content. Researchers from this most recent study stated that, “cherry juice has been shown to decrease oxidative stress and inflammation following strenuous exercise making it possible that these antioxidant and/or anti-inflammatory properties modulated indices of sleep in this study…”
Howatson G, Bell PG, Tallent J, Middleton B, McHugh MP, Ellis J. Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. Eur J Nutr. 2012 Dec;51(8):909-16.
Burkhardt S, Tan DX, Manchester LC, Hardeland R, Reiter RJ. Detection and quantification of the antioxidant melatonin in Montmorency and Balaton tart cherries (Prunus cerasus). J Agric Food Chem. 2001 Oct;49(10):4898-902.
Garrido M, Paredes SD, Cubero J, Lozano M, Toribio-Delgado AF, Muñoz JL, Reiter RJ, Barriga C, Rodríguez AB. Jerte Valley cherry-enriched diets improve nocturnal rest and increase 6-sulfatoxymelatonin and total antioxidant capacity in the urine of middle-aged and elderly humans. J Gerontol A Biol Sci Med Sci. 2010 Sep;65(9):909-14.