Diet and Sleep

Since numerous sources have suggested the influential role of diet in insomnia, this 2019 study assessed the relationship between adherence to a DASH diet and the prevalence of insomnia in adolescent girls. The sample population consisted of 488 adolescent girls aged between 12 and 18 years from various regions of Khorasan Razavi in Northeast Iran. As expected, the girls with higher DASH scores (highest quintile) ate significantly more fruits, vegetables, low fat dairy products, fish, and nuts compared with those with lower DASH scores. Additionally, these participants with higher scores consumed less refined grains, red and processed meat, sugar-sweetened beverages and sweets. As with its relationship with insomnia, higher adherence to the DASH diet correlated with less insomnia cases, when compared with people with lower diet adherence. In fact, the probability of experiencing insomnia was 49% less likely for those with higher adherence to the DASH diet. These results remained true after analysis models were adjusted for potential confounders. Rostami et al. therefore deduce that adherence to DASH dietary patterns was inversely linked with insomnia in adolescent girls.

This 2019 review explores the possible connection between lack of sleep and low intakes of fruit and vegetables, 2 factors thought to contribute to the great disease burden and global mortality rates. Noorwali et al. examines a total of 52 adult human studies on the relationship between sleep and fruit and vegetable consumption. Experimental studies were deemed to provide inconsistent results and be lacking in numbers, while several observational studies appear to show that adults sleeping the recommended 7-9 hours/day also eat the highest amounts of fruits and vegetables. This review highlights the potential mechanisms in which sleep and fruit and vegetable intake are linked, such as homeostatic and non-homeostatic mechanisms (how disrupted sleep influences fruit and vegetable consumption). It was also added that fruit and veg intake may have an effect on sleep through its polyphenol content. Although several potential pathways have been identified, there are limited human experimental studies regarding the impact of polyphenols (in fruits and vegetables) on sleep. Further knowledge on sleep’s interaction with fruit and vegetable intake may aid the reduction of the global chronic disease burden and allow the optimization of sleep.

The purpose of the 2018 inSOMNIA study was to find out how prevalent sleep disorders are among nursing students of the University of Perugia. And at the same time, Gianfredi et al. examined how lifestyle, eating habits, health status and academic performance are linked to night-time and daytime symptoms of the interrupted sleep. The PREDIMED questionnaire was used to reveal the students’ adherence to the Mediterranean diet, a high-tryptophan diet with positive effects on sleep, while sleep disorders were determined using the "Sleep and Daytime Habits Questionnaire". The scores obtained in the PREDIMED questionnaire were associated with BMI, smoking habit, quality of life, and academic progress. To summarize this study’s findings, high prevalence of sleep disturbances was correlated with diet and poor academic progress.

Here, Gangwisch et al. (2020) extracted the data of postmenopausal women who participated in the Women's Health Initiative Observational Study, and investigated the association between glycemic index, glycemic load, and several other dietary measures, with prevalence of insomnia. As well as glycemic index (rating system that demonstrates how quickly food affects the blood sugar levels) and glycemic load (quantitative measure of food’s effect on blood sugar levels), this study looked at added sugars, starch, total carbohydrate, dietary fiber, and specific carbohydrate-containing foods such as whole grains, vegetables, and dairy products. The authors hypothesized that higher glycemic indices (GI) and glycemic loads would correlate to increased incidence of insomnia. Interestingly, greater GI was in fact associated with higher prevalence of insomnia in cross-sectional and longitudinal analyses. Additionally, greater consumption of added sugars, starch, and non-whole/refined grains were each linked with higher odds of incident insomnia. Whereas insomnia was less likely to occur in women who ate more non-juice fruit and vegetables, dietary fiber, and whole grains. To conclude, high-GI diets may elevate the risk of insomnia in postmenopausal women. These high-GI foods should be replaced with minimally processed, whole, fiber-rich carbohydrates.

The primary aim of this 2018 study was to determine the interactions between fruit and vegetables consumption and its polyphenol content, with sleep duration in women in the U.K. Noorwali et al. utilized the data of 13,958 women who participated in the UK Women's Cohort Study, including information on dietary intakes assessed at baseline with the food frequency questionnaire, and the average number of sleeping hours per day reported at the 4-year follow-up. The consumption of one additional fruit portion (of apples, kiwi, oranges, pineapples, or 100% fruit juice) was linked with getting fewer hours of sleep. In fact, eating another portion of cabbage, celery, aubergine, olives, and peppers also correlated with less sleep. The intake of one additional gram of total polyphenols was related to 18 minutes less sleep. The conclusion was that fruit and vegetable consumption, and total polyphenol content were negatively associated with sleep duration. But in defense, the effect sizes observed were small, and the polyphenol classes specifically obtained from eating fruits and vegetables were not connected with sleep. Future research should inspect the timing of the fruit and vegetable eating event in relation to sleep.

The objective of this 2021 study was to determine the association between energy drink use and sleep-related disturbances in young adults recruited from Western Australia (22 years old). The statistics showed that 66% of the 1115 participants never or rarely drank energy drinks (less than once a month), while 17% reported occasional use (>once/month to

In this 2020 study, Pengpid & Peltzer investigated the relationship between fruit and vegetable intake, sleep duration, and sleep quality in a multinational sample of university students. The median age of the 21,027 students from 28 different countries was 20 years. While short sleep was reported in 38.9% of the students, 12.8% managed to get long sleep. Quality of sleep was low in 9.6% of the population, while restless sleep was more common at 19.7%. The study also found that the prevalence of short sleep declined in a linear manner as fruit and vegetable consumption increased beyond ≥2 servings per day. The intake of 2 fruit and veg portions every day was associated with a 21% decrease in incidence of short sleep. Interestingly, the consumption of 5 and 7 servings/day was linked with a 34% reduction in risk of long sleep. Looking at the final adjusted analysis model, 3 fruit and vegetable servings per day appeared to correlate with a 49% drop in probability of getting poor quality sleep. Furthermore, the chances of restless sleep were reduced by the consumption of 5 or more fruit and vegetable portions per day. To summarize, these findings provide evidence of a connection between insufficient fruit and vegetable in the diet and short sleep, as well as an inverse relationship between fruit and vegetable consumption, poor sleep quality, and restless sleep.

In this 2018 study, data from The National Diet and Nutrition Survey was used to determine the relationship between fruit and vegetable consumption and sleep duration. The total sample size included in this study was 1612 adults aged 19-65 years (pregnant and breastfeeding women were excluded). Noorwali et al. announced that participants that manage to get >8 hours of sleep per day (long sleepers) consumed on average 28g/day less fruit and vegetables (total), when compared with those who sleep for 7-8 hours a day (reference sleepers). But it was the short sleepers (< 7 hours/day) that consumed the least fruits and vegetables (24g/day less than reference sleepers) and showed the lowest levels of fruit and vegetable biomarkers (total carotenoids, β-carotene and lycopene). But these relationships were not found to be linear, with reference sleepers having the highest fruit and vegetable consumption levels and the highest concentrations of fruit and vegetable biomarkers. Nevertheless, the conclusion was that fruit and vegetable consumption appeared to be linked with sleep duration.

In this 2020 study, the association between dietary polyphenols and sleep quality was investigated in a sample of Italian adults. Godos et al. administered food frequency questionnaires to assess dietary components, focusing on the individual, total, and subclasses of polyphenols present in the participants’ diets. A significant finding was the inverse relationship between increased intake of lignans and poor sleep quality. Additionally, higher consumption of hydroxycinnamic acid was related to inadequate sleep quality. When examining individual compounds, naringenin and apigenin are flavonoids that were linked with sleep quality, while matairesinol was classed as a lignan. The secondary analysis divided the sample into normal weight and overweight/obese groups, revealing a stronger interaction between certain classes of, subclasses of, and individual compounds with sleep quality. For example, nearly all individual compounds belonging to the lignan class were negatively linked with inadequate sleep quality. However, no associations were found between polyphenol class and sleep quality in the overweight/obese individuals. These results suggest that increased consumption of certain polyphenols may be related with better sleep quality among Italian adults.

This 2020 review focuses on feeding and sleep since they are 2 important behaviors for survival that are subject to strong homeostatic control. Organization and planning is required to ensure that both the energy demands and sleep needs are met. Northeast et al. explains that humans would simply alternate between sleeping and foraging or feeding under ideal conditions. However, when the body is in a negative energy state, there must be a balance between energy conservation and foraging activity. Since the neural circuits that regulate sleep and energy balance are interconnected in mammals and many animal species, this review looks at this circuitry, discussing how homeostatic regulation is modulated by changes in food availability, and outlining the role of the circadian system in adaptation to metabolic stress.

This 2019 study tests the relationship between circadian rhythm differences and food addiction (via insomnia and impulsivity) in university students. The idea is that a person can be identified as being part of a certain chronotype (feeling more efficient in the morning or later in the day for example) using a variety of behavioral, psychological, and biological variables such as appetite levels, regular meal times, sleep times, and melatonin secretion. To obtain these psychological data of the 1323 university students that enrolled, Kandeger et al. used the Morningness-Eveningness Questionnaire, Insomnia Severity Index, Barratt Impulsiveness Scale Short Form, and Yale Food Addiction Scale. The results indicated that evening types (those who feel higher efficiency later in the day) were more susceptible to experiencing insomnia and impulsivity. There was no significant linear relationship between circadian rhythm differences and food addiction. But the study highlights the finding that evening-type circadian preferences was indirectly related to higher food addiction scores mediated by insomnia and impulsivity.

This 2020 review discusses the evidence surrounding the hypothesis that food is a circadian zeitgeber (time cue for the circadian system). While light is the primary cue for the circadian system of humans and animal models, Lewis et al. explain that dietary factors such as meal timing and diet composition are often thought of as the secondary cues. The researchers believe that the development and practice of healthy zeitgeber use may reduce disruption or misalignment within the circadian system (chronobiological strain), which is associated with numerous negative health outcomes. A potential strategy to help facilitate adoption of zeitgeber hygiene is adjusting meal timing and composition. The evidence for food zeitgeber effects specific to humans is notably scarce, although confirming the impact of meal timing and composition on the human circadian system is regarded by some as a vital piece of information with regards to human chronobiology.

Since poor sleep and disturbed circadian rhythm may contribute to excessive food consumption, Vidafar et al. (2020) propose that these 2 factors may also explain the higher risk of obesity found in shift workers. The aim of this study was to explore the relationship between sleep characteristics and hedonic (pleasure-related) control of appetite in shift workers. An online survey was completed by the 63 shift workers (average age 36.6) that participated in this experiment. Weight change after starting shift work was reported by 71% of the whole sample population, while 84% of these people admitted gaining weight since taking up shift work (average weight gained: 11.3kg). Other notable findings include the increased food cravings associated with poorer sleep quality and shorter sleep duration. Moreover, poorer sleep quality and hygiene were both linked with increased motivation to eat palatable foods (greater hedonic drive). The results of this preliminary study have suggested that hedonic pathways may play a role in weight gain in shift workers with disturbed sleep.

Since sugar-sweetened beverages and shortened sleep duration have been linked with the development of obesity, Prather et al. (2016) decided to explore the relationship between these 2 variables among adults (aged 18+ years). Data from the 2005-12 NHANES study was borrowed, considering the adults who slept 7-8 hours/night as the reference group. The results revealed that 13% of the 18,779 adults slept 5 or fewer hours per night. These subjects who slept 5 hours of fewer per night consumed more sugar-sweetened drinks, compared with the reference group. The highest contributors were caffeinated sugary beverages. It was also identified that those individuals who managed ≥9 hours of sleep/night consumed fewer servings of coffee and water, relative to the reference. No association was reported for the consumption of 100% juice, tea, or diet drinks. To summarize the data, short sleep correlated with higher intake of sugary caffeinated sodas, a finding that may have important implications for physical health.

This 2021 study recruited 142 female students from the Department of Nutrition and Food Science at the Semnan University of Medical Sciences through random sampling, and examined them on dietary intake, depression, anxiety, and quality of sleep. The main purpose was to gain an understanding of the association between dietary zinc intake with risk of depression, anxiety, and sleeping issues. After adjusting the analysis model for various factors such as age, economic status, and BMI, Hajianfar et al. (2021) discovered that zinc consumption was strongly linked with higher odds of depression (134% more likely), anxiety (243% increased risk), sleep disorders, and daytime dysfunction. Other analysis models identified connections between zinc consumption with sleep delay and mental quality of sleep. These results suggest the inverse association between dietary zinc intake with mood disorders (including depression and anxiety) and several aspects of sleep disturbances in the Iranian female students.