“Cherry juice could hold the cure to a good night’s sleep,” according to the Daily Mail. It said that volunteers with insomnia enjoyed more sleep after drinking cherry juice than when they drank other juices.
The story is based on a pilot study of 15 elderly adults with chronic insomnia that found that drinking cherry juice had a small beneficial effect on their sleep patterns. Although well designed and carefully carried out, this pilot study was small and the treatment period was only two weeks. As the authors point out, the alleged effects of cherry juice were so slight that people in the study continued to have significant sleep disturbance. Overall, this study, which was funded by a cherry juice manufacturer, cannot provide any firm evidence that cherry juice can ease insomnia.
People with problems going to sleep or staying asleep are normally advised to adopt good sleep hygiene, such as having a fixed time to go to bed, avoiding caffeine and winding down before going to bed. A number of treatments are available for more severe or persistent problems.
Where did the story come from?
The study was carried out by researchers from several US institutions: the University of Rochester, Veterans Affairs Center of Excellence and the University of Pennsylvania. It was entirely funded by CherryPharm Inc., the maker of the tart cherry juice used in the study. The study was published in the peer-reviewed Journal of Medicinal Food.
Neither the Daily Mail nor the Daily Express, which both reported on the study, mentioned that the research was funded by a cherry juice manufacturer. Neither newspaper reported on the limitations of the study or the fact that results were ‘modest’, both of which the study authors have highlighted. The Mail also failed to mention the trial’s small size of just 15 participants.
What kind of research was this?
This was a pilot study, which is a small-scale, preliminary study normally carried out to check if it is feasible to undertake more large-scale research. It was a randomised controlled double blind trial with a crossover design, meaning that each participant received either the juice treatment or a placebo drink for two weeks, followed by an intervening two-week ‘washout’ period and then a two-week course of the alternative drink.
A randomised controlled trial is the best type of study to find out about the effect of a particular treatment because it is carried out under controlled conditions and any effects in the group receiving the treatment can be compared to those seen in the group receiving a placebo (or in some cases, another active treatment).
The researchers say that tart cherries are reported to have a number of beneficial health effects, including sleep enhancement, although little data exists to support these claims. One suggested pathway that might explain possible sleep-promoting qualities, is their relatively high content of melatonin, a substance with sleep-regulating properties. The study aimed to find out if a tart cherry juice improved self-reported incidence of insomnia, when compared to a placebo.
What did the research involve?
The researchers advertised for participants aged 65 and over in local newspapers and through leaflets left in GP surgeries and health centres. Forty-three people were screened by telephone for preliminary eligibility and, of these, 19 people who complained of insomnia, but were otherwise healthy, were scheduled for an interview. After a number of interviews, examinations and tests, including self-reported accounts of their experiences, 15 participants were recruited to the trial.
Inclusion criteria included: experiencing a sleep problem more than three nights a week for at least six months, a score of 10 or more on a validated insomnia severity index (ISI), and either a minimum of 30 minutes of problems getting to sleep (called sleep latency or SL) or waking after the onset of sleep (WASO). People with any medical or psychiatric illness were excluded, and participants were also screened for substance abuse, use of any sedating and hypnotic medications and symptoms of other sleep disorders.
The participants included in the final trial were eight men and seven women with an average age of 71.6 years. The study eligibility tests revealed they had moderate to severe levels of insomnia that was more related to problems staying asleep rather than to getting to sleep.
The study consisted of four two-week periods (a total of eight weeks), with participants divided into two blocks. Each block of participants had two weeks of no treatment, then randomly received either the ‘treatment’ juice or a placebo juice for two weeks. This was followed by a two-week ‘washout’ period to clear any effect of either treatment or placebo from their systems and two weeks of drinking the alternative drink.
The treatment beverage or the placebo drink were consumed as two 8oz (227ml) servings, with one serving in the morning and one in the evening, one to two hours before bedtime. They recorded in a daily sleep diary if any dose was missed or taken at a different time.
The treatment juice used was a juice blended from whole Montmorency tart cherries and apple juice, produced by the manufacturer, while the placebo was a black cherry soft drink mix considered to have a similar taste and appearance to the cherry juice. Both drinks had the same containers and product labels and neither investigators nor participants were informed which cases contained the cherry juice and which the placebo.
Participants used daily sleep diaries to record their sleep patterns and researchers used these to assess sleep continuity, sleep onset, wake after sleep onset, total sleep time and sleep efficiency (a calculation of the time slept, divided by the time spent in bed), as measured by the insomnia severity index. They used a standard statistical method to assess the potential significance of any changes.
What were the basic results?
The researchers conducted various analyses comparing both pre and post-treatment changes within groups and any changes with the cherry juice compared to placebo.
After the cherry juice, there was significant pre-post treatment improvement for all measures including:
- insomnia severity, as measured by the ISI
- the number of minutes that people were awake after the onset of sleep (WASO)
- sleep onset latency (time taken getting to sleep, SL)
- total sleep time (TST)
- sleep efficiency
After the placebo, there was significant pre-post treatment improvement in total sleep time only.
Compared to the placebo the participants found that the cherry juice produced significant reductions in their insomnia severity and in the minutes they were awake for after the onset of sleep (WASO). However, cherry juice was no different to the placebo in terms of sleep onset latency, total sleep time or sleep efficiency.
The researchers also point out that the sizes of all the effects, including the statistically significant ones, were “moderate, and in some cases negligible”. There were no significant improvements on measures of fatigue, depression or anxiety.
How did the researchers interpret the results?
The researchers say their findings suggest that tart cherry juice can modestly improve sleep in older adults with insomnia. They add the size of the effect was such that participants continued to have significant amount of sleep disturbance. They note that the improvements were small when compared with the results of trials of drugs or behavioural interventions for insomnia. However, they do say further studies of the possible sleep-promoting effects of tart cherries are warranted.
This placebo-controlled randomised controlled study was carefully designed and carried out. It used validated methods to assess people’s sleep habits and any changes to them. However, it is too small and has too many limitations to show that tart cherry juice can improve insomnia. As the authors point out, further larger studies would be needed to find out if cherry juice could have sleep-enhancing effects.
It should also be noted, as the authors point out:
- The small sample size limits the ‘statistical power’ to detect any true effects.
- The treatment period was only for two weeks, providing no information on longer-term effects.
- The study depended on people’s self-reporting of sleep rather than assessing it objectively using polysomnographic assessments, which use machines to a range of factors monitor factors such as brain activity and heart rate. The authors point out that other reputable trials have used subjective data.
- The sample was of healthy elderly people so the findings may not apply to other groups.
- The sample mainly suffered from sleep maintenance problems – staying asleep – so any effect cherry juice might have on sleep latency may not be detected by this trial.
- The cherry juice used was a proprietary blend made from fresh, tart Montmorency cherries, so any results may not apply to cherry juice from concentrate or to eating cherries themselves (since participants taking the ‘treatment’ consumed the equivalent of about 100 cherries daily).
- The participants may have been able to taste the difference between the cherry juice and the diluted placebo drink. Knowing which drink they were consuming may have influenced the behaviour and responses of the participants.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Daily Express, 14 July 2010
Daily Mail, 14 July 2010
Links to the science
Journal of Medicinal Food 2010; 13: 579-583