People who have trouble sleeping may find help by drinking two glasses of tart cherry juice a day, researchers in Britain say. Researchers at Northumbria University and colleagues found when adults had two glasses of tart cherry juice daily, they slept 39 minutes longer, on average, and had as much as a 6 percent increase in overall sleep efficiency -- significantly less non-sleep time in bed -- compared to when they drank a non-cherry, fruit cocktail. Twenty healthy adults drank two servings of tart cherry juice concentrate -- 100 percent pure Montmorency juice concentrate per serving, diluted in a half-pint of water -- or a non-cherry fruit drink for seven consecutive days at a time. They had one serving when they woke up, and another before bed. The researchers tracked the sleep habits of participants and found significant improvements in sleep behaviors after they drank the cherry juice, most notably longer sleep time, less daytime napping and increased overall sleep efficiency -- the ratio of time spent in bed to time spent sleeping -- compared to when they drank the non-cherry juice drink. The study, published in the European Journal of Nutrition, suggests the sleep benefit may come from the melatonin an antioxidant critical for sleep-wake cycle regulation. Each serving of the tart cherry juice concentrate was estimated to contain the equivalent of 90 to 100 tart cherries, providing a significant level of melatonin in the juice and ultimately in the bodies of the participants, the researchers said.