'No evidence' that melatonin helps with jet lag
hormone melatonin does not help people with sleep problems like jet
lag, conclusions that have questioned by an industry association.
Melatonin, secreted by the pineal gland, is stimulated by the onset of darkness, and is an important actor in the body's circadian cycle - the body clock. Previous studies, including two systematic reviews have reported that melatonin is effective in dealing with the symptoms of jet lag.
The hormone is currently available in the US as a 'dietary supplement'. According to the Nutrition Business Journal, US sales of melatonin were $67 million in 2004.
The researchers from the University of Alberta wrote in the British Medical Journal (doi:10.1136/bmj.38731.532766.F6): "This review showed that melatonin does not have a significant effect on sleep onset latency in either disorder or on sleep efficiency in people with sleep disorders accompanying sleep restriction."
The Alberta team reviewed data from 25 different studies, and quantified melatonin in terms of efficacy, sleep onset latency and safety. No safety concerns were noted.
When compared with placebo, the hormone was reported to have no significant effect on secondary sleep disorders. However this type of disorder refers to serious neurological disorders, quite different from jet lag.
When evaluating jet lag studies, and despite the admission that some of the source studies did not report adequately on content, quantity and/or formulation of the melatonin, the researchers concluded: "There is no evidence that melatonin is effective in treating jet lag and shiftwork disorder."
Dr Daniel Fabricant, Vice President of Scientific Affairs for the National Nutritional Foods Association (NNFA), an industry association, told NutraIngredients-USA.com that new claims were "misleading."
"There are several limitations with this review. Firstly, their choice of studies has no clear-cut exclusion criteria. Secondly, the study populations are not the best. Most of the studies [in the review] are for secondary sleep disorders which are serious neurological problems," said Fabricant.
On the issue of jet lag, Fabricant noted that the researchers did not examine the effects of melatonin on daytime fatigue. Previous studies have reported that the hormone improved daytime functioning.
"How you feel the next day is an important issue for people with jet lag," said Fabricant.
The review does not give anything new to the subject, Fabricant added, and that the same researchers only recently called for more randomized clinical trials on melatonin before any conclusions could be drawn (Journal of General Internal Medicine, Dec 2005, Vol. 20, pp. 1151-1158).
About 70 million Americans are said to experience sleeping problems. The National Sleep Foundation estimates that sleep disorders costs the US about $100 billion per year in lost productivity, medical expenses, property damage and sick leave.
