Does it work?

Can tart cherries help cure insomnia?

BACKGROUND

Tart or sour cherries have recently become very popular as health-promoting juices or food supplements. Tart cherries are the fruit of the tree Prunus cerasus,which is closely related to the wild or sweet cherry, Prunus avium. The latter are the cherries that are eaten fresh. Tart cherries are smaller and more acidic and, because of that, are usually cooked or processed before being eaten.

Tart cherries also have a long history of medicinal use. Traditionally they were used to treat gout and other painful conditions. More recently, they have been recommended for preventing everything from insomnia, heart disease and muscle pain to cancer. They are now being promoted as one of the super fruits which we cannot do without.

EVIDENCE FROM STUDIES

Tart cherries and their juice contain several compounds which act as antioxidants and have anti-inflammatory activity. The cherries also contain vitamin C, vitamin A, small amounts of vitamin E and several important minerals. Tart cherries also contain melatonin, a natural hormone which is involved in sleep regulation. However, the amount of melatonin varies widely with the different varieties of tart cherry available.

Tart cherry juice received a lot of media attention early this year after a study was published involving older adults with insomnia. Tart cherries were hailed as a cure, although the results were more modest than some headlines suggested. The study was randomised and double-blinded, but it was a pilot study. These are preliminary studies that enrol a small number of people to determine whether it is feasible to conduct a larger study and to see what sorts of adjustments would be needed to its design.

This particular pilot study involved 15 adults, who were 65 years of age or older and had chronic insomnia. The participants were randomly assigned to drink either a commercial tart cherry juice or a placebo juice for two weeks. They took a two-week break, and then for the next two weeks drank the alternative juice to the one they had in the first period. The study was funded by the juice manufacturer.

When drinking tart cherry juice, the people fell asleep quicker. However, they did not sleep longer or have better quality sleep. The researchers noted that the effects were moderate, and that for some people they were negligible. The improvements were similar to those found with valerian and some studies of melatonin, but considerably less than those found with prescription sleep aids or some relaxation therapies.

Other claims about the health benefits of tart cherries have similarly received little testing in humans. Three small studies with marathon and long-distance runners have shown that tart cherry juice may prevent oxidative damage. Muscle soreness and weakness after endurance events were reduced in runners who had been drinking cherry juice for up to a week before their race compared with those who drank a placebo juice. Researchers hypothesised that the high levels of antioxidants in the juice prevented oxidative damage, which normally occurs during endurance training and competition.

PROBLEMATIC ASPECTS

No adverse effects have been reported in studies of tart cherry juice. Large numbers of tart cherries have been consumed without problems.

RECOMMENDATIONS

Tart cherry juice contains a variety of compounds which are good to have as part of a healthy diet. While the results of the studies conducted to date are interesting, all of them were with small groups of people over very short periods of time. Tart cherry juice is being recommended for long-term conditions, and studies would need to be continued over months or years to assess whether the short-term benefits continue. At the same time, no problems have been found with the juice. Tart cherries are a nutritious fruit and a good source of vitamins, minerals and antioxidants, but there is little evidence that these products treat or prevent any particular illness.

Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He is author of Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007