Eat two kiwis for a good night's rest
If you have trouble sleeping, and - very sensibly - prefer not to use sleeping pills, then nutritionists at Taipei Medical University in Taiwan may have a solution to your problem. In the Asia Pacific Journal of Clinical Nutrition the Taiwanese write that you sleep better if you eat two kiwis before going to bed.
Serotonin in foods
The researchers hit on the idea of investigating the sleep-enhancing properties of kiwi fruit from a study done at Duke University in the US in the eighties. [Am J Clin Nutr. 1985 Oct; 42(4): 639-43.] In this study American researchers analysed the amounts of serotonin in common foods. The table below comes from the article.
Serotonin is a precursor of the sleep hormone melatonin. In the body enzymes do a cut-and-paste job to convert the amino acid L-tryptophan into 5-HTP, then 5-HTP into serotonin, and serotonin into melatonin. The route is shown here.
The same cycle also takes place in some plants, such as tomatoes, cherries and bananas. That's why these fruits contain serotonin and melatonin, and why there are studies that suggest that consuming cherries, for example, improves quality of sleep.
The table below shows that kiwis also contain serotonin.
The researchers did an experiment with 29 men and women aged between 29 and 55 who had mild sleep problems. Every day for four weeks they ate 2 kiwis an hour before going to sleep.
The tables below show that after the four-week period their quality of sleep had improved. After getting into bed, the subjects fell asleep 5 minutes earlier and slept 40 minutes longer.
"Consumption of 2 kiwifruit nightly 1 hour before bedtime for 4 weeks resulted in improved sleep onset, duration, and efficiency in adults with self-reported sleep disturbances", the Taiwanese summarise.
"The results of this study suggest that further research into the sleep-promoting mechanisms of kiwifruit may be warranted."
The study was financed by Zespri, a marketing organisation for kiwi growers. [zespri.com]
Asia Pac J Clin Nutr. 2011;20(2):169-74.
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