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

Abstract

Objectives Carbohydrate is the nutrient most 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. Methods The Web of Science and Medline were interrogated using terms related to carbohydrate and sleep. Papers were retained if two diets, differing in the percentage of calories coming from carbohydrate, had been contrasted using either polysomnography or actigraphy. Measures considered with polysomnography included sleep onset time; sleep efficiency; rapid eye-movement (REM) and slow wave sleep (SWS). Measures examined from actigraphy included: sleep efficiency; duration of sleep. Meta-analysis was conducted using Review Manager 5.2 (Cochrane) using a random-effects model. Results With the polysomnography measures six studies met the inclusion criteria. A lesser consumption of carbohydrate was associated with more SWS (SMD = 0.47; CI 0.06 – 0.88; P = 0.02; I2 = 0%) and less REM (SMD = – 0.47, CI –0.87– –0.07, P = 0.02, I2 = 0%). A lower intake of carbohydrate was also associated with a shorter time before falling asleep (P = 0.03; I2 0%). Sleep efficiency is 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 = 0.06). However, using actigraphy those eating less carbohydrate were more sleep efficient (SMD = 1.25; CI 0.35 – 2.15; P = 0.007; I2 = 0%). Conclusions No study had the high level of carbohydrate needed to raise tryptophan; rather studies had enough protein to reduce the uptake of tryptophan. A novel possibility is that blood glucose levels modulate sleep. Glucose metabolism varies; it is less during SWS and greater with REM. There 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. As SWS is believed to be restorative and aid plasticity, increasing SWS with lower carbohydrate have may functional implications. Funding Sources No external funding.

Mediterranean Diet and Sleep Features: A Systematic Review of Current Evidence

“…Both trans-fatty acids and long-chain saturated fatty acids can activate Toll-like receptors (TLRs) on the surface of immune cells, including microglia in the brain, which initiates a signaling cascade that leads to the production of pro-inflammatory cytokines; the pathways activated involve the Nuclear Factor-kappa B (NF-κB) and the Mitogen-Activated Protein Kinase (MAPK) signaling pathways (including extracellular signal-regulated kinase (ERK), c-Jun n -terminal kinase (JNK), and p38 MAPK, which can lead to the expression of inflammatory mediators and the activation of transcription factors that promote inflammation in macrophages, monocytes, and monocyte-derived dendritic cells [ 47 ]. Concerning carbohydrates, the main source of daily energy in the Mediterranean diet should be provided by whole-grain products: a high dietary content of carbohydrates is generally related to better sleep, while, conversely, lower intake has been associated with a longer time spent in slow-wave sleep and less time in rapid-eye-movement (REM) sleep [ 48 ]. Moreover, the high content in complex molecules and fiber would provide a lower glycemic index, which has been related to improved sleep quality [ 49 ].…”

Nutritional Elements in Sleep

“…They serve as the main source of fuel for our body to function and, hence, influence our sleep. As per a meta-analysis studying the effect of low versus high dietary carbohydrate content on sleep parameters, the former was associated with shorter time before falling asleep and higher sleep efficiency, which is defined as the percentage of time spent asleep relative to the total time in bed [ 91 ]. Not only is the amount of carbohydrates important in influencing sleep architecture but also the type of carbohydrates, especially the glycemic index, as well as the timing of their consumption.…”