Influence of Carbohydrate on the Stages of Sleep – A Meta-Analysis

Abstract

\n \n \n Carbohydrate is the nutrient\xa0most commonly said to influence sleep: it is proposed that a high intake increases the uptake of tryptophan by the brain, where it is metabolized into serotonin and melatonin. As this mechanism depends on the relative amount of carbohydrate and protein, studies were reviewed where diets differed in these macro-nutrients.\n \n \n \n The Web of Science and Medline were interrogated using terms related to carbohydrate and sleep.\xa0Papers were retained if two diets, differing in the percentage of calories coming from carbohydrate, had been contrasted using either polysomnography or actigraphy.\xa0Measures considered with polysomnography included sleep onset time; sleep efficiency; rapid eye-movement (REM) and slow wave sleep (SWS).\xa0Measures examined from actigraphy included: sleep efficiency; duration of sleep.\xa0Meta-analysis was conducted using\xa0Review Manager 5.2 (Cochrane) using a random-effects model.\n \n \n \n With the polysomnography measures six studies met the inclusion criteria.\xa0A lesser consumption of carbohydrate was associated with more SWS (SMD\xa0=\xa00.47;\xa0CI\xa00.06 – 0.88; P\xa0=\xa00.02; I2\xa0= 0%) and less REM (SMD = – 0.47,\xa0CI –0.87– –0.07, P\xa0=\xa00.02, I2\xa0= 0%).\xa0A lower intake of carbohydrate was also associated with a shorter time before falling asleep (P\xa0=\xa00.03; I2 0%).\xa0Sleep efficiency\xa0is the percentage of time spent asleep, relative to the total time in bed. Using polysomnography there was a trend for better sleep efficiency to be associated with with a lower intake of carbohydrate, although it just missed significance (P\xa0=\xa00.06).\xa0However, using actigraphy those eating less carbohydrate were more sleep efficient (SMD\xa0=\xa01.25;\xa0CI 0.35 – 2.15; P\xa0=\xa00.007; I2\xa0= 0%).\n \n \n \n No study had the high level of carbohydrate needed to raise tryptophan; rather\xa0studies had enough protein to reduce the uptake of tryptophan.\xa0A novel possibility is that\xa0blood glucose levels modulate sleep.\xa0Glucose metabolism varies; it is less during SWS and greater with REM.\xa0There are many reports associating the nature of sleep with glucose tolerance. As several hormones control glucose levels, some stimulated by the level of glucose, there is a need to consider diet hormonal interactions.\xa0As SWS is believed to be restorative and aid plasticity, increasing SWS with lower carbohydrate have may functional implications.\n \n \n \n No external funding.\n