Blackmores Institute

Results of the narrative review found that consumption of high carbohydrate diets, foods containing tryptophan, melatonin and phytonutrients, such as those found in cherries, could improve sleep quality and quantity.
 
 “Since inadequate sleep (duration and/or quality) can negatively affect several physiological and psychological processes, identifying simple lifestyle strategies that assist with improving sleep outcomes in the general population is paramount,” the authors said.
 
 With growing scientific attention on the relationship between dietary intake and sleep in recent years, specifically to understand how specific dietary factors directly influence sleep outcomes, the authors claim their review will clarify the effects of diet on sleep metrics.
 
 Examining 32 studies the narrative analysis revealed four key themes: tryptophan consumption/depletion, dietary supplements, food items and macronutrients.
 
 “Tryptophan-containing foods improved sleep indices compared with controls. For example, compared with controls, an increase in total sleep time, sleep efficiency, and immobile time was noted after a week of tryptophan-rich (60 mg) cereal consumption in older adults. Furthermore, participants also experienced less difficulty in falling asleep and less waking at night, total activity, and fragmented sleep,” the authors reported.
 
 According to the authors, reducing availability of tryptophan prevents synthesis of serotonin and subsequently reduces sleep quality.
 
 “The mechanism for this centres around tryptophan competing with other large neutral amino acids to cross the blood brain barrier, where it is converted to serotonin, the precursor to the sleep-promoting hormone, melatonin.”
 
 Studies included in the review that looked at the use of dietary supplements found that zinc supplementation in individuals with below-optimal zinc improved global sleep quality scores on the PSQI, subjective sleep quality, and sleep onset latency scores. Polyphenols were found to result in lower sleep disturbances, and greater total sleep duration and sleep quality.
 
 “One study investigated the sleep-promoting effects of consuming different cultivars of Jerte Valley cherries (sourced from Spain) in middle-aged and elderly individuals. The effect of each cultivar on sleep quality varied, likely due to the differing levels of serotonin and melatonin. However, in general, significant improvements were found in middle-aged participants for total sleep time, sleep efficiency, the number of awakenings, total nocturnal activity, assumed sleep, and sleep onset latency. Meanwhile, older adults experienced decreases in the number of awakenings, immobility, and sleep onset latency, and increases in assumed sleep,” the authors said.
 
 “Although this narrative review has highlighted certain foods and nutrients with the potential to promote sleep, when recommendations for nutrient intake are made, it is also important to consider timing of food intake, a concept termed chrononutrition. 
 
 “Chrononutrition combines the health, behaviour, and chronobiology disciplines to understand the optimum timing of food intake for health and performance. Eating at a time that contradicts our circadian system, such as nocturnal eating, can entrain rhythms in peripheral clock tissues, such as the liver, and cause misalignment for metabolic processes, glucose homeostasis, gastrointestinal motility, and digestive processes.”
 
 “This narrative review highlights research linking dietary intake and sleep outcomes. The consumption of high carbohydrate diets, foods containing tryptophan, melatonin, and phytonutrients (i.e., cherries) indicates promising results for improved sleep quality and quantity. Further research is needed to understand the mechanisms underlying many of these effects,” the authors concluded
 
 
 Source:
 Nutrients. 2020. DOI:<a href="https://www.mdpi.com/2072-6643/12/4/936">10.3390/nu12040936</a>

A review on how dietary patterns may affect sleep has found that certain phytonutrients, amino acids and high carbohydrate foods, were linked to improved sleep outcomes.

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