Diet and Human Performance

It has been observed that people who work shifts experience a variety of biological, psychological, and behavioral issues. In this study by Erden et al. (2023), the authors examined the eating attitudes and behaviors of 92 health professionals (nurses, doctors, emergency medical technicians [EMT], security personnel, and medical secretaries) working shifts in a demanding environment (emergency department), and investigated the associations between anxiety, depression, stress levels, and eating behaviors (emotional eating, restrictive eating, and external eating), in terms of sociodemographic and clinical characteristics. Study participants submitted the Depression, Anxiety, and Stress Scale (DASS), the Dutch Eating Behavior Questionnaire (DEBQ), and a sociodemographic data form. Analysis of the results revealed that, when the "emotional, external, and restricted eating" sub-dimensions of eating behavior of emergency service workers were evaluated, anxiety, depression, being a nurse-emergency medical technician, higher levels of stress, being a woman, diet history, and working 24-hour shifts were substantially associated with "emotional eating." Moreover, "extrinsic eating" was found to be linked to being single, higher levels of depression, working 24-hour shifts, and younger age, while “restrictive eating” was linked to a higher body mass index (BMI), waist circumference, and diet history. The authors note that being single, being female, working 24-hour shifts, having a history of poor nutrition, having an undergraduate education, and being a nurse-EMT were factors found to increase the likelihood of developing eating behavior disorders. "Extrinsic eating" was linked to being single, having higher depression levels, working 24-hour shifts, and being younger. The authors highlight that their findings show how emotional eating scores and anxiety, depression, and stress scores are related. Furthermore, the authors discovered strong associations between scores for restricted eating and waist circumference, body mass index, and diet history. The authors recommend the identification of specific eating behavioral disorders while treating eating behavior issues to plan effective work programs and to improve the quality of service as long shift workers, such as those who work 24-hour shifts, are more likely to develop eating behavior issues. [NPID: Depression, anxiety, stress, sociodemographic factors, restricted eating, external eating, emotional eating, emergency service workers]

In order to maintain an active roster of hospital staff throughout the day, shiftwork is inevitable. However, shiftwork is known to be associated with several drawbacks, including loss of sleep and lifestyle disruptions (physical activity, dietary consumption, metabolism). As the level of evidence exploring the metabolic and dietary characteristics of medical staff in training who participate in shiftwork remained unsatisfactory, Mota et al. (2013) conducted their study to investigate the potential impact of shiftwork on resident physicians’ anthropometrics, dietary intake, sleep patterns and metabolism, and whether there would be any observed differences between genders. Data were collected on several parameters from a sample of 72 resident physicians (20 of which were men), including anthropometry (height, weight, body mass index [BMI], and waist circumference), nutrition (3-day dietary recall evaluated by the Adapted Healthy Eating Index), physical activity (Baecke questionnaire), sleep quality (Pittsburgh Sleep Quality Index; PSQI), fasting metabolism (lipids, cortisol, high-sensitivity C-reactive protein [hs-CRP], glucose, and insulin), and sleepiness (Epworth Sleepiness Scale; ESS). A majority of the participants were noted to be substantially overweight or obese (65% of men and 21% of women), with men demonstrating higher BMI scores and reporting more weight gain after starting their residencies compared to female residents. While both genders practiced poor nutritional habits, such as high consumption of sweets, cholesterol, saturated fats, caffeine, and low consumption of fruits and vegetables, men had substantially higher PSQI scores compared to women (7.5 for men, 5.9 for women). Metabolic analyses showed that women had substantially higher serum levels of cortisol and high-density lipoprotein cholesterol when compared to men, while the majority of participants displayed serological and metabolic derangements (elevated low-density lipoprotein cholesterol, prevalent hypertriglyceridemia and elevated hs-CRP). Furthermore, an increased pervasiveness of daytime sleepiness and inferior sleep quality was observed in the participants. The authors conclude that their findings raise the necessity of developing health surveillance protocols for residents and to reevaluate the current division of resident labor, in addition to placing an approval process prior to assigning medical residents extra night shifts in order to prevent any adverse health events. [NPID: Metabolic variables, residency training, shiftwork, nutrition, sleep]

In this parallel-group study by Wilson et al. (2022), the authors investigated the efficacy of a physical activity (PA), sleep and nutrition program on the body composition, cardiorespiratory fitness, and healthy habits in a population of 125 airline pilots who are overweight. The participants were divided into a control or an intervention group, which engaged in a 16-week customized program addressing sleep hygiene, healthy diet, and PA. Health data were collected (at baseline and after the conclusion of the study) on body mass, girth, maximal oxygen consumption (VO2max), blood pressure, plank hold, resting heart rate, and push-ups, in addition to self-reports on health, including sleep quality, weekly PA, fruit, and vegetable consumption and self-rated health. Analysis of the results demonstrated a substantial impact of the intervention program on enhancing all measured health outcomes (except for the weekly walking component, which did not induce a significant impact). Objective health measures investigated were substantially enhanced in the intervention group compared to controls, a trend which was also observed in self-reports on sleep quality, fruit and vegetable intake, moderate-to-vigorous PA, and self-rated health. The authors conclude that their results showcase the impact of a customized 16-week PA, healthy eating, and sleep hygiene intervention on the short-term enhancement of the physical and mental health of overweight airline pilots, however, more studies are necessary to evaluate the longitudinal maintenance of these observations. [NPID: Aerobic capacity, fruit and vegetable intake, lifestyle medicine, physical activity, nutrition, weight loss]

In this study by Borasio et al. (2022), the authors examined the links between neuropsychological reading and writing performance and serum polyunsaturated fatty acid (PUFA) levels, in a population of 30 students (mean age = 10.83 ± 1.43 years). Before the beginning of the experiment, the participants were assessed for reading skills and a myriad of visual and auditory neuropsychological functions pertaining to reading and writing performance. Analysis of the results revealed the existence of a moderate to strong direct, positive relationship between reading and writing abilities and PUFA levels, and with PUFA levels and neuropsychological scores. In addition, PUFAs were found to indirectly enhance the accuracy scores of visual-spatial cueing when comparing the right and left visual fields as part of writing accuracy assessment. The authors comment that their results demonstrate the role of visual-spatial attention in the process of reading and writing, highlighting that visual low-level processes may be responding favorably to increased serum omega-3 PUFAs. [NPID: PUFA, cueing task, dyslexia, flanker effect, phonological processing, reading, visual processing, visual spatial attention, writing]

The negative influence of feeling burnt out on mental state, health, and work goes without saying. In this study by Penttinen et al. (2021), the authors investigated the links between dietary habits and symptoms of burnout using data from a 2015 cross-sectional study conducted on a population of 630 female employees. The participants’ symptoms of burnout were evaluated using the Bergen Burnout Indicator (BBI) and their dietary habits via the food frequency questionnaire (FFQ), which were further categorized into healthy and unhealthy categories using the Nordic Nutrition Recommendation standards. The results revealed significant reductions in symptoms of burnout with dietary intake of healthy food (especially low fat dairy products, vegetables, fruits, berries, and white meat) irrespective of age, education, physical activity or symptoms of depression. In conclusion, the authors demonstrate a reduction of burnout symptoms with dietary intake of healthy foods, and highlight the role of dietary balance and diversity in enhancing well-being while at work. [NPID: Burnout, mental health, nutrition]

Detrimental dietary habits play a role in increasing the risk of chronic diseases suffered by shift workers. Limited research has examined the relationship between shift work, diet and other associated factors, like sleep and mood, which may impact shift workers’ dietary choices. In this study by Heath et al. (2019), the authors investigated the links between shift work, sleep, diet and mood, in a population of 52 nurses (of which, 46 are female. Age 39.8 ± 12.4 years) over the course of 14 days. This study (within- and between-subjects design) collected data using food diaries (containing a minimum of three recorded days per shift, morning, afternoon and night), visual analog scales for mood (happiness, anxiety, depression, stress, fatigue), and actigraphy for sleep estimation. In addition, the study utilized the foodworks nutrition software to estimate energy and macronutrient intake, and the Standard Shiftwork Index to account for confounders such as demography and work-related variables. Through analyzing the collected data, the authors first compared night and morning shifts, and found that working during afternoon shifts was associated with a reduction in energy intake and with lower levels of stress. In the same vein, consuming more calories and more fats (especially saturated) was linked to experiencing elevated levels of stress. Morning shifts were linked to a decreased intake of carbohydrates, while night shifts correlated with lower levels of protein consumption. Finally, the results demonstrated a relationship between decreased quality of sleep and elevated carbohydrate and protein consumption. In conclusion, when comparing nighttime and daytime, afternoon shifts showed reductions in energy consumption. Symptoms of stress, depression and anxiety depend on shift type and energy consumption, and are associated with elevated intake of fats. The authors comment that shift workers would benefit from dietary interventions tailored to shift type and mood. [NPID: Shift work, nursing, healthcare, sleep, diet, depression, anxiety, fatigue]

Despite a growing body of research outlining how a healthy diet can protect from depression, the number of studies investigating these protective effects in healthcare workers combating the COVID-19 pandemic is insufficient. This spurred Miki et al. (2022) to determine the cross-sectional relationship linking the frequency of balanced meal consumption— where a balanced meal contains a staple food (e.g., rice, bread, and noodles), a main dish (e.g., fish, meat, eggs, and soy products), and a side dish (e.g., vegetables, mushrooms, potatoes, and algae)—and depressive symptoms among 2,457 hospital workers during the COVID-19 pandemic. Participants documented their depressive symptoms through the Patient Health Questionnaire-9 (PHQ-9), and the number of days they ate two or more balanced meals every week. The participants were ubsequently divided into four categories as follows: ≤1 day/week, 2-3 days/week, 4-5 days/week and daily. The authors observed a prevalence of depressive symptoms amongst healthcare workers of 14.8%, with more chance of suffering from depressive symptoms in relation to less balanced meals consumed per week. The odds of suffering from depressive symptoms were found to be lowest in those who ate balanced meals daily, and highest in those who ate balanced meals ≤1 day/week. Thus, the authors conclude that hospital workers eating less well-balanced meals are more likely to experience depressive symptoms during the COVID-19 pandemic. [NPID: COVID-19, balanced meals, depressive symptoms, depression, epidemiology]

In their study, Ge et al. (2021) set out to investigate the effect that truck driver’s dietary habits, had on their driving behaviors, and whether fatigue experienced by truck drivers had any contributory impact. Data from the study participants (389 male truck drivers) was collected using the Food Frequency Questionnaire (FFQ), the Multidimensional Fatigue Inventory (MFI), and the Positive Driver Behaviors Scale (PDBS) and the Driver Behavior Questionnaire (DBQ). The results highlighted four dietary patterns adopted by truck drivers: animal-derived foods, staple foods, snacks, and vegetables. Data analysis showed that the vegetable-rich pattern had a direct positive impact on driving habits, whereas the animal-derived pattern led to more driving mistakes and traffic infractions. The snacks dietary pattern was linked to negative driving behavior. Staple foods, on the other hand, had an indirect positive effect on driving behavior. Furthermore, the results demonstrated that the level of fatigue experienced by drivers was found to influence the choice of dietary pattern, and subsequently, driving behavior. [NPID: Dietary pattern, truck drivers, fatigue, driving behavior, accidents]

While workers are being encouraged to get enough sleep, do physical activities, and eat a healthy diet to stay productive at work, Cho & Kim (2022) claim that there has yet to be a study that provides a theoretical framework or empirical evidence on the association between employees’ unhealthy eating behaviors and the quality of their performance. This present study tests a moderated mediation model to evaluate the connection between healthy and unhealthy lifestyles, and personal well-being and performance at work. Ninety-seven full-time workers were monitored daily for 2 weeks. It was revealed that employees’ unhealthy eating behavior in the evening led to emotional (guilt) and physical (stomachache, diarrhea) strain the next morning. Moreover, those who experienced these physical and emotional strains in the morning also showed decreased performance quality (less helpful and exhibiting more behaviours related to withdrawal) in the afternoon. Furthermore, emotional stability was discovered to moderate the relationship between unhealthy eating behavior and morning strains. In other words, employees with higher emotional stability tended to feel less negative emotions and experience fewer physical symptoms. [NPID: lifestyles, performance, workers, employee, workforce, eating at work]

The aim of this 2018 study was to explore how work-family conflict, eating style, and unhealthy eating relate to one another. The participants (586 Malaysian adults) completed a questionnaire on demographics, work-family scales, and eating style measures (restrained, emotional, external eating and food consumption). Shukri et al. found that their theory was true. The data showed that family-to-work conflict (FWC), emotional eating and external eating were positively associated with unhealthy food consumption. The impact of family-to-work conflict on eating was moderated by emotional eating. There was no evidence suggesting that body mass index (BMI) and its interactions explain the relationships that exist between work-family conflict, eating style, and unhealthy eating. These findings back up previous research that revealed that emotional eating can strengthen the link between elevated stress (such as conflict) and more unhealthy food choices. Overall, this study has demonstrated that eating styles can explain the association between work-family conflict and unhealthy eating. [NPID: emotional eating, unhealthy eating, eating style, family and work, conflict, stress, family stress, restraining eating, external eating, Malaysia, Malaysian]

A total of 60 physicians, nurses and nursing assistants were recruited for this 2017 randomized trial. The participants were provided with lunch, snacks, and bottled water during each shift during the 8-week intervention. As part of the cross-over study design, the subjects alternated between intervention and control. The healthcare staff were assessed on their reaction time, mood, and dietary intake. The aim of this study was to determine the impact of increasing the availability of healthy meals and water in the workplace on healthcare workers. The hospital staff were found to consume less fat and polyunsaturated fatty acids during the intervention period than during the control period, while their carbohydrate, fiber, and water consumption levels were higher. However, the intervention did not affect reaction time nor mood in the sample. Among the sixteen health care staff working on shifts, only water intake significantly improved in the intervention period than in the control period. But they reported higher vigor, and lower fatigue and mood disturbance scores while participating in the intervention. Thus, providing workers with healthy meals, snacks, and water during their working hours may be an effective strategy to improve their dietary consumption. Plus, drinking more water may be associated with less fatigue and better vigour and mood in shift-working healthcare workers. [NPID: healthcare work, nurses, doctors, physicians, staff, healthy eating, water, intervention]

This robust observational/cross-sectional study (2019) conducted on 2942 employees of one of the biggest Iranian industrial manufacturing companies, Esfahan Steel Company, aimed to classify the workers into subgroups representing varying levels of mental health profile, and to examine its correlation with dietary patterns. After evaluating the study population on psychological distress, anxiety and depression through the use of Hospital Anxiety and Depression Scale (HADS) and General Health Questionnaire (GHQ-12), the three main dietary patterns “western”, “healthy” and “traditional” were identified. Based on the factor mixture model, the vast majority of the population (91.2%) could be classed as ‘low mental health problems’, and the remaining 259 individuals as ‘high mental health problems’. The results suggested the employees who adhered to a more Western and traditional dietary pattern were more likely to be in the high mental health problems group, while those in the highest tertile of healthy dietary pattern showed lower odds in being classed as having high mental health problems. These findings could urge workplace health promotion policymakers to change their approach in improving mental health, and encourage further research into altering dietary habits and its effect on psychological well-being in employees. [NPID: performance, Iran, psychological distress, anxiety, depression, Western-style diet, WS diet, workplace, health promotion]

(2020) Lessem and her team support the implementation of a whole-food plant-based diet (WFPB) in reducing risk of developing diet-related diseases and since most people haven’t been counseled on this dietary pattern, an experiential education program was designed for 30 healthcare professionals (nurse practitioners, registered nurses, physicians) to learn about and implement the special diet for 3 weeks. The aim was for the healthcare providers to expand their knowledge, increase acceptance of the WFPB, and improve likelihood of counselling patients on this particular dietary pattern. Participants completed preintervention and postintervention questionnaires assessing dietary intake, knowledge, weight, mood, energy, benefits, barriers, self-efficacy, and likelihood of continuing to follow, or counsel patients about a WFPB diet. Reduced intake of animal-derived foods, higher consumption of WFPB foods, greater mood, energy and loss of weight were seen in the healthcare professionals. Self-efficacy improved and perceived barriers to following and counseling about a WFPB diet declined, resulting in the participants being more likely to continue with the intervention diet and discuss with patients. Since a three-week intervention altered the healthcare workers’ knowledge, skills and attitudes about WFPB diets, Lessem and colleagues are keen on seeing other providers accepting the diet, leading to more awareness in patients and helping to reduce the current burden of diet-related chronic diseases. [NPID: performance, whole foods, plant-based diet, nurse practitioners, registered nurses, physicians, self-efficacy, chronic disease]

This recent 2019 study addresses the lack of research on how factors associated with shift work and diet, such as sleep and mood, can have an impact upon shift workers’ diets, and thus investigates the relationship between the four: shift work, sleep, mood and diet. A total of 52 nurses (46 female, mean age 39.8) participated in a 14-day within- and between- subjects design study, having mood measured in the form of happiness, anxiety, depressive mood, stress and tiredness) using visual analog scales, as well as their sleep through actigraphy, and macronutrient and energy intake (in kilojoules) through a foodworks nutrition software. Food diaries were completed for a minimum of three days per shift type (morning, afternoon, night). The covariates (demographic and work-related variables) were used to select predictors, which were used in the final model if deemed important. The results showed that working an afternoon shift was associated with a lower energy intake and lower levels of stress (both p-values<0.01) compared to morning and night shifts. Higher levels of stress were associated with a higher energy intake (β=35.3, P<0.01) and a higher percentage of fat (ß=0.1, P=0.05) and saturated fat (β=0.1, P<0.01). Compared to the other shift types, morning shift was associated with lower carbohydrates (β= -4.3, P<0.01) and night shift was associated with lower protein (β= -2.7, P=0.03). Lower sleep efficiency was associated with a higher carbohydrate intake (β= -0.4, P<0.01) and a lower protein intake (β=0.25, P<0.01). This study suggests that afternoon shifts are associated with lower energy consumption compared to morning and night shifts, while negative mood (stress, depression, anxiety) was found to be associated with higher fat intake. Negative mood mediated the association between shift type and energy intake. Therefore Heath and co. (2019) state that dietary interventions for shift workers should also consider mood and shift type into their strategy. [NPID: performance, shift work, sleep, mood, nurse health, happiness, anxiety, depressive mood, stress, tiredness, depression, anxiety, morning shift, night shift, sleep efficiency]

(2017) A review on the ways we sometimes fail to look after ourselves in the workplace, discussing particularly the importance of hydrating adequately and nutrition at work which are both essential to provide optimal care for our patients, to maximise performance (as even the aviation industry have admitted the importance of taking care of ourselves). Parry and colleagues (2017) mention from experience they have noticed clinicians do not drink enough fluids during the day or skip lunch while caring for patients, particularly evident during an all-day operating list with long and complex procedures. Some operating theatre staff do not even have breakfast regularly and so, this review raises awareness of how we jeopardize our health taking in inadequate fluids or nutrition, leading to impaired performance, tiredness and headaches, and may even compromise our own health and the care provided for the patients. [NPID: performance, workplace nutrition, aviation industry, fluid intake, beverages, water intake, impaired performance, tiredness, headaches]

This 2019 study hypothesized that working conditions can influence a person’s diet and thus reviews the published literature analysing the association between work-related factors (such as work hours, shift work, job, physical and mental strain, support) and quality of diet. The 16 selected articles were found by performing a literature search on PubMed for those available online, written in English, published between 2000 and 2017, and set in high-income countries. Although there was some evidence of unhealthy dieting among shift workers, data on the diet quality in association with other work-related factors, such as number of hours worked, physical, mental, job strain, and worksite support were scarce. Tanaka et. al (2019) encourages additional studies to implement a different design to investigate the association between work-related factors and quality of workers’ diets. [NPID: performance, workplace nutrition, shift work]

(2019) To provide a real insight into the implementation and effectiveness of workplace health promotion performed in an Arab country, Altwaijri and fellow researchers (2019) evaluate a wellness program designed to enhance overall well-being of hospital employees in Riyadh, Saudi Arabia. The outcomes assessed included physical activity, diet, absenteeism, work productivity, workplace satisfaction and stress. Results showed promising signs for the health program put in place, as significant improvements were seen in the employees’ physical functioning and average water and fruit consumption. Furthermore, implementation of the program seems to have significantly reduced average intake of soft drinks by the workers, and the number of days of absence in the workplace in a 3 month-period. With positive outcomes for diet and physical function, the findings suggest this health promotion program successfully enhances well-being in these employees of a Saudi Arabian hospital. [NPID: performance, workplace health promotion, Saudi Arabia, Arab, physical activity, diet, absenteeism, work productivity, productivity, workplace satisfaction, stress, fruit, health promotion]

(2018) Since mental health is relevant in job performance, this cross-sectional design study explores the association of major dietary patterns and stressful life events with intensity of psychological problems in 3063 Iranian industrial employees. To form the psychological problems profile, participants were assessed on depression and anxiety [Persian validated version of Hospital Anxiety and Depression Scale (HADS)] and psychological distress [General Health Questionnaires (GHQ)]. Stressful life events dimensions were extracted through the use of factor analysis and self-perceived frequency and intensity of stressful life events (SLE) questionnaire, while the food frequency questionnaire (FFQ) aided with the dietary patterns categorisation. Data indicated a positive association between adherence to the Western and Iranian traditional diet with psychological distress in the employees, while those who adhered more to the healthy diet saw more positive psychological distress scores (even after adjusting for life stressors). It was also found that personal life stressors and socioeconomic stressors had significantly direct association with psychological stress profile scores. Although Yazdi et. al address a few limitations of this study, it can be said that healthy diet adherence can be related to better psychological health, whereas life stressors (such as personal stressors) may not have beneficial effects on mental well-being. With regards to job productivity, this research may prove helpful. [NPID: performance, stress, depression, anxiety, dietary patterns, Western-style diet, WS diet, Iranian diet, Iran, well-being, job productivity, productivity]