The aim of this study was to investigate the effect of the ingestion of tomato before bed on obese postmenopausal women's urinary 6-sulphatoxymelatonin (aMT6s) level and sleep quality. We quantified melatonin concentrations in beefsteak tomato, black tomato, and two commercial tomato juices and found that beefsteak tomato contained the highest level of melatonin. In this 8-week open-label, randomized controlled dietary intervention trial, 36 subjects completed the entire trial. The tomato group ate 250 g of beefsteak tomatoes 2 h before sleep for 8 weeks. Blood and urine samples were collected at the baseline and in the 8th week and were analyzed. The Pittsburgh Sleep Quality Index (PSQI) in the tomato group significantly decreased with time (p for trend = 0.0297). After 8 weeks of the beefsteak intervention, all components of the PSQI in tomato group had significantly improved, and their aMT6s level was 10-fold significantly higher than that of the control group. Therefore, supplementation with beefsteak tomato before sleep can increase circulating melatonin and improve sleep quality in obese postmenopausal women.
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