Diet, Sleep, and Fatigue

In this scoping review by Burrows, Fenton & Duncan (2020), the authors compile the available evidence examining the relationship between sleep and dietary intake (encompassing free-living, laboratory-based, and mixed experimental designs), paying further consideration to the influence of geographical and subpopulation representation in the interpretation of study outcomes, spurred by the evidence-based links between sleep quality and dietary intake playing a role in the predisposition to chronic diseases. Through searching five online databases (searching for publications that met inclusion criteria from 1970 to 2017), 109 studies were found to investigate the impact of diet on sleep outcomes, and 20 studies were found to investigate the impact of sleep interventions in association with dietary findings. A majority of the sleep interventions reported were laboratory-based, while dietary interventions were mostly implemented in free-living settings. Studies that investigated the use of sleep intervention did so exclusively in terms of sleep duration, with three studies conducted using total sleep deprivation, and 17 other studies investigating the impact of restricted sleep hours (5.5 hr/night) on participant dietary intake. On the other hand, studies investigating dietary interventions utilized supplements, with the majority including caffeine (49 out of 66 studies). The authors comment that further avenues of the relationship between diet and sleep quality should be explored in future studies, such as dietary habits, dietary quality, and detailed sleep components like sleep hygiene, timing, and quality. [NPID: Diet, diet quality, scoping review, sleep, sleep health]

Studies investigating sleep quality and the role of the negative inflammatory impact of poor sleep in the pathology of mental disorders and chronic illnesses are insufficient. In this cross-sectional study by Godos et al. (2019), the authors investigated the relationship between sleep quality and the inflammatory impact of dietary intake in a population of adults (participants of the Mediterranean healthy Eating, Aging, and Lifestyle [MEAL 2014-2015], n = 1935). Data on sleep quality was collected using the Pittsburgh Sleep Quality Index, while dietary evaluation was conducted using food frequency questionnaires and the Dietary Inflammatory Index (DII®). Analysis of the results revealed a significant reduction in sleep quality and increased sleep latency in individuals with high DII scores compared to their peers. The authors conclude that sleep quality is negatively impacted by increasing dietary inflammatory potential, an observation that can be utilized in tailoring dietary interventions that target systemic inflammation intending to enhance sleep quality and ameliorate cognitive decline. [NPID: Sleep quality, cognitive decline, dementia, mental health, cohort, Italy, dietary inflammatory index, diet, inflammation, dietary patterns]

In this cross-sectional study by Makowski et al. (2019), the authors examined the links between sleep-related impairment (SRI) and dietary patterns in a population of 245 community physicians. Participants submitted a wellness survey (March 2016) outlining details on their dietary habits, which enabled the recognition of three distinct patterns that participants followed, namely, a high protein, high saturated fat and sugar, and a plant-based pattern. Analysis of the results demonstrated a significant decrease in SRI score with increasing plant-based dietary consumption, and a significant increase in SRI score with increased saturated fat and sugar consumption, while protein diets did not impact SRI scores. Studies have shown that diet may mitigate SRI, and through their results, the authors demonstrate the impact of a plant-based diet and decreased dietary intake of fats and sugars on SRI. These results may provide useful insight into tailoring workplace nutrition interventions to help support physicians. [NPID: Physician well being, diet, dietary patterns, nutrition, sleep, alertness, fatigue mitigation]

In this study by Kaçar et al. (2020), the authors investigated the links between perceived fatigue and nutritional habits through identifying fatigue predictors in a population of 543 non-pregnant obese women who are trying to lose weight. Participants submitted an online questionnaire at baseline and after joining a weight management program, documenting data on age (19-49 years), weight, food frequency questionnaire, and perceived fatigue. Analysis of the results revealed that participants who consumed more vegetables suffered from lower levels of fatigue compared to those who adopted a diet of high fats and simple carbohydrates, in addition to losing more weight. The authors comment that their study highlights the novel associations between fatigue and dietary patterns in a population of obese women who are trying to lose weight prior to, and after enrolling in, a weight management program. [NPID: Dietary pattern, fatigue, weight management, principal component analysis]

In this study by Campanini et al. (2017), the authors investigated the links between adherence to healthy dietary patterns, such as the Mediterranean diet (MD), and sleep duration and quality in a population of 1,596 older adults (volunteers of the seniors-ENRICA cohort, ≥ 60 years of age). Sleep duration (in hours) was recorded, and MD adherence was scored using the Mediterranean Diet Adherence Screener (MEDAS). Variables like lifestyle, morbidity, sleep duration, poor sleep indicators, and sociodemographics were taken into account. Follow-up duration approximated 2.8 years. Analysis of the results revealed that participants in the highest category of MD adherence demonstrated higher odds of increasing their sleep duration by ≥2 h/night and had lower odds of suffering from poor sleep (≥2 indicators of poor sleep quality), and changes in sleep quality, compared to participants in the lowest category of MD adherence. Thus, the authors conclude that MD fidelity results in a lower incidence of sleep changes and improvement in sleep quality in older adults. [NPID: Epworth Sleepiness Scale, MEDAS, Mediterranean diet, sleep duration changes, elderly, sleep quality]

Several works demonstrated the medicinal components of the kiwifruit, including antioxidants and serotonin that could help treat sleep disorders. In this free-living, self-controlled diet study by Lin et al. (2011), the authors investigated the impact of kiwifruit consumption on sleep patterns (onset, duration, and sleep quality). Study participants (n = 24, females = 22, age 20-55) ate two kiwifruits one hour before bedtime every night for four weeks and had their sleep evaluated using the Chinese version of the Pittsburgh Sleep Quality Index (CPSQI), using a 3-day sleep diary, and using an Actigraph sleep/activity logger watch to record several subjective and objective parameters of sleep (quality of sleep, time to bed, the onset of sleep, waking time after sleep onset, time of waking up, total sleep time, self-reported sleep onset latency, and sleep efficiency before and after the intervention). The results demonstrated a substantial improvement in subjective CPSQI score, sleep onset latency, and waking time after sleep onset. A significant increase was also noted in total sleep time and sleep efficiency. Thus, the authors conclude that eating kiwifruit may enhance sleep onset, efficiency, and duration in adults who report sleep disturbances and that further research is necessary to understand the benefits of the kiwifruit. [NPID: Kiwifruit, sleep disturbance, adults]

This 2022 study examined the newly proposed hybrid diet, the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) dietary pattern, on its connection with sleep quality and sleep-related outcomes. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), while day-time sleepiness and insomnia were tested through standard questionnaires. Mental health was also evaluated using the 21-item depression, anxiety, and stress scale (DASS-21). As for diet, dietary information was collected through a food frequency questionnaire, which was used to calculate a MIND score (indicates adherence to the MIND dietary pattern). The subjects were 400 male health professionals with an average age of 48 years. While adherence to the MIND diet was not found to be associated with depression, anxiety, or stress, individuals with the greatest adherence to the MIND diet were less likely to have lower sleep quality, compared to those least adherent to the MIND diet. Conforming to the MIND dietary pattern also appeared to be linked with lower odds of daytime sleepiness. With regards to insomnia, following the MIND diet did not strongly correlate with the severity of the sleep disorder, but higher adherence was associated with lower odds of insomnia. [NPID: sleep, sleep quality, insomnia, diet, MIND diet, dietary pattern, Mediterranean diet]

While past studies have shown that sleep can influence dietary choices, this 2012 article explores whether food consumption can affect sleep. The purpose of this review was to discuss the data associating diet with sleep, and to find out if the nutrients obtained through food before bedtime does matter. The authors present the evidence behind traditional sleep-promoting foods such as milk and certain herbal products. The data showcased here are mostly based on clinical trials involving human subjects. Another point of discussion was the mechanisms behind the study observations. The most helpful foods for sleep may be those that can modulate the availability of tryptophan or affect synthesis of serotonin and melatonin. While there are clear physiological links between diet and sleep, further research is warranted. [NPID: sleep, diet, review, dietary choices, nutrients, dietary habits, lifestyle]

This 2020 study investigated the possible effect of eating red meats on apnea (the stopping of breathing) and hypopnea (a disorder in which shallow breaths are taken for 10 seconds or longer while asleep). The participants were patients recently diagnosed with mild or moderate to severe obstructive sleep apnea (OSA). Every patient was aged between 21 and 70 years old, free of other chronic diseases, and had not changed their dietary habits for at least 6 months before the assessments. Food frequency questionnaires and 24-hour dietary recalls were used to evaluate food intake, while the polysomnography recorded data about the patients’ sleep. Multiple logistic regression analysis models determined that eating higher quantities of total red meat or unprocessed red meat was related to higher values of apnea and hypopnea indices. Compared with patients in the lower intake quartile of total red meats, those eating the most red meats (in top quartile) were 3 times more likely to have severe obstructive sleep apnea. These results suggest that red meat consumption is correlated with severity of obstructive sleep apnea. [NPID: obstructive sleep apnea, sleep, sleep apnea, red meat, meats, diets, nutrition, hypopnea, dietary patterns]

The aim of this 2021 study was to find out how diet can affect obstructive sleep apnea (OSA). The researchers specifically looked at whether there are connections between certain eating habits and obstructive sleep apnea among Chinese adults. A total of 9733 participants were selected from the baseline survey of the Guangzhou Heart Study. Food frequency questionnaires allowed analysis of food intake, while obstructive sleep apnea was reported using the Berlin Questionnaire. The data indicated that eating fried food at least once a week was associated with increased risk of OSA, while eating fruits at least once a day correlated with a 26% lower risk of sleep apnea. The study also identified 3 dietary patterns, one of which (pattern 3) contained higher levels of animal innards, fried food, salted food, carbonate, and non-carbonated beverages. Increased adherence to this pattern 3 was linked with an increased risk of sleep apnea, when compared with lower dietary pattern adherence. Patterns 1 and 2 were not found to be related to risk of OSA. In summary, eating fruits more frequently may be coupled with lower risk of obstructive sleep apnea, whereas consuming high levels of animal innards, fried food, salted food, carbonated beverages, and non-carbonated beverages may increase the risk of sleep apnea. [NPID: sleep apnea, sleep, dietary patterns, diet, China, fats, nutrition, diet, fried food, fruits]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, depression, anxiety, zinc, sleep disorders, daytime dysfunction, Iran, students]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, obesity, shift work, night shift, appetite control, hedonic drive]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, circadian rhythm, food addiction, impulsivity, chronotype, appetite, meal times, melatonin]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, polyphenols, Italy, lignans, hydroxycinnamic acid, naringenin, apigenin, flavonoids, matairesinol, obesity]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, fruit, vegetables, FV intake, students, restless sleep]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, fruit, vegetables, polyphenols, U.K., United Kingdom, women, FV intake]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, Perugia, academic performance, school, Med diet, Mediterranean diet, tryptophan, quality of life, smoking]

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. [NPIDs: insomnia, sleep, sleep quality, sleep duration, DASH, adolescence, Iran, sweets, sugar]