Diet and Stress

There is considerable overlap between the brain control of stress and the neural regulation of hunger and energy balance. The cortico-limbic striatal system may become dysregulated as a result of recurrent acute stressor exposure, increasing allostatic load (exposure to endocrine or neural responses), and impairment of the integration of postprandial homeostatic and hedonic signals. Bini et al. (2022) underscore the need to comprehend the brain pathways through which stress causes changes in hunger that might result in weight gain. to ascertain the effects of glucocorticoids on the metabolic, neurological, and behavioral elements that may be responsible for the relationship between glucocorticoids, hunger, and the risk of obesity. To measure regional cerebral blood flow (CBF), the authors conducted a randomized, double-blind, cross-over study with hydrocortisone or saline overnight infusion followed by a fasting morning perfusion magnetic resonance imaging. Flyers and online advertisements were used to enlist 16 healthy, slim people (Mean BMI = 22.4 ± 2.2 kg/m2, Mean age = 26.4 ± 6.7 years), whom were assessed for cortisol levels, metabolic hormones, and hunger on the Visual Analog Scale (VAS). Analysis of the results revealed that, In the hypothalamus and associated cortico-striatal-limbic areas, hydrocortisone dramatically reduced whole-brain voxel-based CBF responses compared to saline. Less reduction in CBF (hydrocortisone minus saline) in the medial OFC, medial brainstem and thalamus, left primary sensory cortex, and right superior and medial temporal gyrus predicted hydrocortisone-related increases in appetite. In comparison to saline CBF groups, hydrocortisone significantly increased appetite as measured by the VAS pre-scan, insulin, glucose, and leptin, but not other metabolic hormones. On the hydrocortisone day but not the saline day, hunger evaluations were also strongly correlated with plasma insulin levels. The authors conclude that specific brain networks of prefrontal, emotional, reward, motivation, sensory, and homeostatic regions that underlie control of food intake become affected by increased glucocorticoids at levels similar to those experienced during psychological stress, increasing fasting hunger and decreasing regional cerebral blood flow. [NPID: Cortisol, glucocorticoids, hunger, stress, fMRI]

The excretion of glucocorticoids (prominent physiological stress hormones) is linked to levels of urinary sodium. Consuming large quantities of sodium in the diet is commonplace, and is linked to negative cardiovascular outcomes. In this study by Costello et al. (2022), the authors investigated the impact of a high salt diet on the function of the hypothalamic-pituitary-adrenal axis and concurrent glucocorticoid levels in a population of male C57BL/6 mice. The mice were placed on a high salt diet and observed from the second week of the experiment up to the eighth. The authors noted that following 2 weeks of a high dietary salt intake, the mice demonstrated increased sensitivity of the hypothalamic-pituitary-adrenal axis, seen by increased glucocorticoid secretion in response to stress (restraining). In addition, increased dietary salt intake elevated the levels of messenger RNA (mRNA) encoding for corticotropin-releasing hormone (Crh) and proopiomelanocortin (Pomc) in the hypothalamus and anterior pituitary, indicating heightened levels of hypothalamic-pituitary-adrenal axis activity, on top of an increase in the expression of cerebral and hepatic 11β-hydroxysteroid dehydrogenase Type 1 enzyme mRNA, responsible for glucocorticoid regeneration. The increase in circulating glucocorticoids was also accompanied by a reduction in hepatic mRNA encoding for circulating Corticosteroid-Binding Globulin. In the mice hippocampus, Fkbp5 mRNA (a marker of exposure to elevated glucocorticoid levels) was increased. Furthermore, the increase in circulating glucocorticoid levels leads to water retention by the kidneys (increase in the vasopressin marker copeptin). This increase was also coupled with a rise in anterior pituitary Tonebp and Avpr1b, which may indicate a role for vasopressin and copeptin in elevating the sensitivity of the hypothalamic-pituitary-adrenal axis. The authors conclude that elevated levels of dietary salt enhance the responsiveness to basal and stress-related glucocorticoid secretion, modulating glucocorticoid homeostasis on central, peripheral, and cellular levels. [NPID: Cortisol, glucocorticoid excess, glucocorticoid receptor, salt, stress]

In previous works by Ball et al. (2022), the authors demonstrated the potential role played by chronic stress in stimulating the recurrence of palatable food-related behaviors in male rats. Sex was shown to be an essential determinant of the neurobehavioral outcomes of stress exposure, which spurred the authors to investigate whether sex plays a role in the recurrence of behaviors following the exposure to stress, in addition to exploring the potential influence of anxiety which is known to raise the odds of suffering from stress-related pathologies, using an experimental rat model. Rats were evaluated for anxiety and separated into high- or low-trait anxiety phenotypes using elevated plus maze testing, while stress was introduced in extinction training via a period of daily restraining (from zero to 90 minutes/day, for a total of seven days). Finally, the rats’ palatable food-related behaviors were evaluated through cue- and pellet-priming. Analysis of the results revealed that chronic stress exposure decreased the intensity of cue-induced reinstatement of food-seeking behaviors in female rats, despite showing a higher initial response, compared to male rats. On the other hand, a history of exposure to stress lead to an increased response in low-anxiety phenotype rats, and a decreased response in high-anxiety phenotype rats, to pellet priming-induced reinstatement of palatable food-seeking behavior, while female rats showed no response irrespective of anxiety phenotype and prior stress exposure. The authors conclude that trait anxiety and sex may play a role in modulating the likelihood of recurrent behaviors following chronic stress events, providing a potential avenue to aid in eating disorder and obesity treatment customizations. [NPID: Anxiety, chronic stress, food seeking, reinstatement, relapse, sex differences]

Poor dietary habits are prevalent in individuals suffering from substance use disorders, for example, lower intake of fruits and vegetables, which deprives them of the positive impact on physical and psychological health gained from consuming fruits and vegetables. Recent evidence demonstrated the potential of fruit smoothie supplements on improving the health status of opioid-dependent individuals undergoing rehabilitation therapy. In this multicenter, randomized controlled trial by Fadness et al. (2022) termed FruktBAR, the authors aim to evaluate the impact of supplementing the diet of individuals receiving opioid agonist therapy to treat opioid dependence with a fruit smoothie intervention compared to treatment standards. With a target to investigate 302 individuals on opioid agonist therapy, the authors aim to administer a daily fruit smoothie supplement (250 ml smoothie containing pineapple, apple, banana, mango, blueberry, orange, coconut, passion fruit, blackcurrant, and lime) and evaluate the participants for psychological distress using the Hopkins Symptom Checklist (SCL-10) after 16 weeks, comparing the results to the control population on standard care. In addition, physical functioning (4-minutes step-test), perceived fatigue, health-related quality of life, biochemical indicators of fruit intake, and inflammation will be documented for further analysis. The authors intend to discover the benefits or drawbacks of fruit smoothie interventions as adjuvant treatment options for the standards of care currently available in practice. Should the intervention prove beneficial, further studies would be warranted. [NPID: Addiction, opioid, dietary supplement, fruit smoothie, adults, psychological health, rehabilitation]

Individuals with higher educational qualifications (for example, graduate degrees) were presumably more likely to attain a job and financial security during the COVID-19 pandemic, which could affect the dietary and lifestyle choices such individuals can enjoy, and consequently overall mental wellbeing. On the other hand, those who lost their sources of income during the pandemic suffered from enforced lifestyle changes, which affected their mental health adversely. In this study by Begdache et al. (2021), the authors investigated the trends of dietary and lifestyle factors affecting mental health before and during the COVID-19 pandemic, in a sample of adults from various educational backgrounds. Being a part of a larger study investigating the effect of dietary habits on mood, the data was collected before the COVID-19 pandemic from 2,853 adults and later on from 692 adults during the pandemic (from March 2020 onwards) using Food-Mood questionnaires submitted anonymously via social media platforms. The results of the study revealed that holders of graduate degrees ate more vegetables, less fast food, exercised more often, used more nutritional supplements (multivitamins, fish oils), and experienced less mental stress compared to adults without graduate degrees, who had a higher frequency of missing breakfast, but were unexpectedly found to consume more fruits, meats, and high glycemic index meals, used more nutritional supplements and exercised frequently, yet experienced higher levels of mental stress. The authors commented that participants who hold graduate degrees suffered fewer interruptions to their dietary and lifestyle routines (and in turn, fewer stressors), experienced more physical health gains and had lower odds of suffering from mental stress, while participants without graduate degrees suffered from higher dietary and lifestyle disparities, which may account for the observed higher levels of mental stress. In summary, the authors conclude that educational level is a potential contributor to dietary and lifestyle habits during the COVID-19 pandemic and to overall mental wellbeing. [NPID: Diet, exercise, educational status, mental health, population characteristics, lifestyle changes, pandemics, COVID-19]

The impact of stress on our bodies is not just skin-deep. Stress doesn’t just “get under” our skin, it also causes neuroimmune and neuroendocrine derangements that impact overall mental and physical health, causing effects that are more substantial and critical early on in life (in the setting of adverse childhood experiences [ACEs] or what is known as early life stress [ELS]). In this review by Hantsoo et al. (2021), the authors investigate if psychosocial stress leads to microbiome derangements by reviewing evidence derived from human and animal studies that implemented experimental parameters to induce stress, such as chronic stress, acute laboratory stressors, perceived stress, stressful life events, in-utero stress or ELS, in addition to exploring their impact on the microbiome. Furthermore, the authors investigated the body of evidence on the use of dietary modalities targeting the intestinal microbiome in the presence of stress. Analysis of the available evidence showed that ELS, chronic stress, and acute laboratory stress lead to significant derangements of the microbiome in rodents, while ELS and perceived stress negatively impact the microbiota of humans. While preliminary evidence demonstrates the efficacy of pre-, pro-biotics, and omega-3 fatty acid dietary interventions on ameliorating stress-induced microbiome derangements, especially in rodents, more research is necessary to validate these observations. The authors conclude that stress may indeed get “into the belly” by negatively impacting neuroimmune, neuroendocrine, and microbiome-gut-brain axes. [NPID: Adverse childhood experiences, gut-brain axis, hypothalamic pituitary adrenal, HPA, inflammation, microbiota, stress]

In this cross-sectional study by Begdache et al. (2021), the authors highlight the crucial distinction in brain maturation that needs to be acknowledged when tailoring mental health therapies for young (18-29 years) and more mature (30 years and above) patient populations, in addition to acknowledgement of gender-influenced morphological differences, and endeavored to discern dietary and lifestyle factors influencing mental health in these sub-populations. Collecting data across a 5-year period (2014-2019, including 2,628 records), the analyses revealed that mental stress in young women and men was linked to high caffeine and fast food intake, and that moderate to high levels of exercise and frequently having breakfast significantly reduced mental stress levels. A significant degree of overlap was observed between young and mature women, although a reduction in mental stress due to high fruit intake was also observed in mature women. Mature men were found to display significantly lower levels of mental stress with higher degrees of education and with a moderate consumption of nuts in their diet. The authors conclude that their results display the necessity for tailor-made dietary and lifestyle interventions to improve mental health and wellbeing. [NPID: Young adults, mature adults, biological sex, mental distress, mental wellbeing, personalization of diet, brain maturity]

Begdache & Patrissy (2021) discuss how the relationship between the modifiable risk factors of mental distress (diet, dietary practices, and exercise) may be so intricate that individual factors also influence mental health differently when combined with a pattern. In addition, gender and maturity level contribute towards a person’s psychological health. This study therefore split the participants by age and gender and analyzed the combined and individual relationships between food groups, dietary practices and exercise to better understand their links with mental distress. Adults of 30 years and over were asked to complete the food-mood questionnaire that was distributed around several social media platforms. The results suggested that mental health was more strongly associated with dietary factors in women than in men. Furthermore, mental distress and exercise frequency were related to various lifestyle and dietary patterns, supporting the concept that modifying lifestyle and dietary factors can enhance mental wellbeing. [NPID: stress, mental distress, diet, exercise, gender, maturity level, social media, well-being]

While physical activity and healthy eating appear to offer protection against stress and negative affect, Schultchen et al. (2019) point out a few studies that have demonstrated a reduction in these behaviors in the face of stress and negative affect. This present study therefore inspected the relationship between these behaviors in daily life using ecological momentary assessment (EMA). For 7 days, 51 university students responded to six daily prompts on items such as stress, emotional experience, physical activity duration, and healthy eating. The results indicated that higher stress, negative affect, and lower positive affect were all linked with lower subsequent physical activity. Inversely, higher physical activity levels were associated with less subsequent stress and negative affect, and more positive affect. There was no such interlink between stress and affect with healthy eating. This study concludes that carrying out physical activity was correlated to improved mood and less stress/negative affect over the next few hours. [NPID: stress, physical activity, exercise, emotion]

This 2015 article summarizes what was said in the "Stress, Palatable Food and Reward" conference, a symposium in which four presentations were given by neuroscientists who mainly work with complex relationships among stress, food intake and emotion. Firstly, Dr Ulrich-Lai showcased her work on discovering the mechanisms by which the rewarding properties of sweet palatable foods help relieve stress. Dr Fulton also presented her rodent model study demonstrating the stimulating effects of long-term dietary lipid consumption, including its withdrawal, on stress-related outcomes. Dr Wilson then talked about his group’s research on how social hierarchy-related stress affects food intake and diet choice in female macaques, while the last speaker Dr Petrovich discussed her research program focused on defining the circuitry (shared between the cerebral cortex, amygdala, and hypothalamus) responsible for diminishing the urge to eat during emotional threat in rats. The complexity of the physiological and behavioral factors connecting stress, food intake and emotional state were apparent. [NPID: stress, palatable food, reward, emotion, cerebral cortex, amygdala, hypothalamus]

Pasquali (2012) writes that obesity is believed to develop as a result of people’s inability to adapt to chronic environmental stress exposure that is mediated by a dysregulation of related neuroendocrine axes. One axis that plays a major role in this context is the hypothalamic-pituitary-adrenal axis. But the author reports that a person’s sex also affects their ability to adapt to chronic stress. This is highlighted as stress-related chronic diseases develop following certain pathophysiological events. The regulatory impacts of sex hormones are thought to play a role in this development. The stress experienced may alter feeding as well, with variation according to sex again. Carrying out experimental studies on humans and animals can increase the understanding of the specific phenotypes of obesity that are connected to the chronic exposure to stress. Doing so can potentially sprout novel ideas and treatments for obesity. [NPID: stress, obesity, adaptation, stress exposure, HPA axis]

This 2019 review presents findings from human studies to explain the bidirectional relationships between stress, diet, and the gut bacteria, and their effect on immune function and health. Stress and depression can modulate the composition of gut microbiota, which can lead to changes in eating behaviors e.g. promoting intake of highly palatable foods, and alter mood due to the release of metabolites, toxins and neurohormones. It has been proposed that probiotics supplementation may attenuate the increased stress responsiveness and heightened depression risk induced by the gut bacteria. [NPID: stress, diet, gut bacteria, microbiome, gut microbiota, gut-brain axis, palatable foods, metabolites, toxins, neurohormones, probiotics, depression]

This 2020 review evaluated the literature on the associations between diet, stress, obesity and psychiatric disorders related to stress since the nature of these relationships is not well understood. Bremner et al. (2020) learnt that diet and obesity can have direct impacts on mood, with certain aspects of diet stimulating inflammation in the process which has led to research on polyunsaturated fatty acids (PUFAs) as treatments for depression. While stress-related mental disorders may induce dietary changes likely to affect weight, stress or predisposition alone may lead to obesity and stress-related mental disorders such as depression and posttraumatic stress disorder (PTSD). There are likely to be bidirectional relationships between these various factors. This review also addresses the increasingly reported connection between the gut and the brain, which relates the gut microbiome with brain function and thus mood and behavior. Since this identifies another way diet can influence mental health and disorders, this relationship is probably mediated by the same areas of the brain and peptides that are involved in both mood and appetite. Elucidating the relationship between diet, stress and mood and behavior could provide crucial implications for the treatment of both stress-related mental disorders and obesity. [NPID: stress, obesity, mood, polyunsaturated fatty acids, PUFAs, depression, PTSD, appetite]

Roohafza et al. (2013) studied the relationship between food intake and stress levels in an Iranian adult population, using the 9549 participants (aged 18+) of the third phase of Isfahan Healthy Heart Program (IHHP). The subjects were divided into two groups (high- and low- stress) according to their stress levels [assessed by General Health Questionnaire-12 (GHQ-12)]. Those individuals assigned to the low-stress group were significantly younger, had lower LDL cholesterol readings, were less likely to be current smokers, tended to do more physical activities and have higher education levels. The 49- item Food Frequency Questionnaire (FFQ) revealed greater consumptions of unsaturated oils, grains, fruits, vegetables, meat, and dairy products in the low-stress group, while they included less saturated oils in their diets and had lower Global Dietary Index (GDI) scores. After adjustments were made based on sex, age, smoking, and physical activity, stress level was reported to be significant positive associated with GDI (OR=1.24) and saturated oils (OR=1.17), whereas stress levels were inversely related to consumption of unsaturated oils (OR=0.84), fruits and vegetables (OR=0.83), meat (OR=0.88), and dairy products (OR=0.88). This significant positive relation between dietary intake and stress emphasized the need to consider psychological factors in dietary recommendations and also pay close attention to diet when managing highly stressed individuals. The causal relationship between stress and dietary factors should be investigated in the future in prospective longitudinal studies. [NPID: stress, Iran, LDL, smoking, saturated oils, psychological factors]

In this review, Gonzalez & Miranda-Massari (2014) explains how higher levels of stress follows unhealthy dietary habits, which results in greater and greater health problems over time as the issues remain unresolved. Prolonged stress can enhance the body’s metabolic needs, leading to increased nutrient use and excretion. This can then result in nutrient deficiency, which is worsened further by stress. In this way, diet and stress can have detrimental consequences on human health. [NPID: stress, metabolism, nutrient deficiency]

In this chapter, O’Connor & Conner (2011) discuss the impact of stress on health and eating behavior, including the conflicting associations of stress with increased saturated fat consumption and decreased overall calorie intake. Some studies have linked stress with increased intake of snacks in adults and adolescents, although these results do not completely prove the effect on health. Stress is thought to influence health directly (through autonomic, neuroendocrine, and biological processes) and indirectly through behavior changes. Now there is considerable evidence pointing to the importance of stress-induced eating behavior changes in health outcomes. This review not only highlights the current knowledge on the effects of stress on eating behaviors but also identifies the remaining gaps in research which require addressing in the future. [NPID: stress, saturated fat, snacking, autonomic processes, neuroendocrine, biological processes]

Research on interactions between calorie intake, gambling, and impulsive and addictive-related behaviors is limited. Thus, Chamberlain et al. (2017) investigate the relationship between fat/sugar consumption with gambling behaviors and other psychopathology measures related to addiction. The study discovered a correlation between increased fat and sugar intake with lower education levels and being male. However, a significant negative association was revealed after controlling for these variables between sugar and fat intake with gambling and anxiety scores. Additionally, consuming more sugar was strongly related to higher depressive scores, greater alcohol consumption, lower self-esteem, and increased prevalence of one or more mental disorders. While the research team did not find significant relationships between dietary sugar and fat with ADHD symptoms, presence of impulse control disorders, Barratt impulsiveness, or cognitive functioning, these overall findings suggest fat/sugar consumption is strongly linked with symptoms of gambling pathology, but not so much with other aspects of impulsivity and behavioral addiction investigated. However, alcohol intake is an exception. This study proposes that education on healthy eating may be crucial in communities heavily influenced by gambling. The mediating mechanisms between calorie intake and gambling symptoms (e.g. determining the influences of environmental factors or joint dysfunction of brain reward pathways) should be considered in future research. [NPID: stress, gambling, impulsiveness, impulsivity, fat, sugar, education status, alcohol, self-esteem, ADHD, reward]

Since high-fat and high-sugar foods have been recently associated with possessing addictive qualities, Yau & Potenza (2013) address stress as a great influence in the development of addiction, which creates further links with increased risk of obesity and other metabolic diseases. Chronic stress alters eating habits and hyperpalatable food consumption, possibly leading to alterations in allostatic load and the triggering of neurobiological adaptations that encourage compulsive behavior. Various factors have been implicated with these changes, including the hypothalamic-pituitary-adrenal (HPA) axis, glucose metabolism, insulin sensitivity, and other appetite-related hormones and hypothalamic neuropeptides. It can be proposed that chronic stress affects the mesolimbic dopaminergic system and other brain regions involved in stress/motivation circuits. It may be multiple pathways synergistically potentiating reward sensitivity, food preference, the desire for hyperpalatable foods, and inducing metabolic changes, while individual susceptibility to obesity and the types of stressors can affect this equation also. To develop effective preventative and treatment strategies for obesity and related metabolic diseases, this review suggests fully elucidating the associations and interactions between stress, neurobiological adaptations, and obesity. [NPID: stress, high-fat, high-sugar, addiction, obesity, metabolic disease, chronic disease, palatable foods, neurobiological adaptations, mesolimbic dopaminergic system, dopamine, reward, motivation]

To assess anxiety’s relationship with calorie intake and food cue perception, this 2016 study assessed 55 twins (26 complete, 3 incomplete pairs) on state and trait anxiety using the State-Trait Anxiety Inventory and allowed the subjects to eat freely at a buffet while monitoring food consumption. Before the buffet, the participants were provided with standardized meals, with functional magnetic resonance imaging (fMRI) scans being performed on each individual before and after these meals. The study also involved the twins viewing blocks of fattening and non-fattening food images, and non-food objects during these fMRI scans. The results showed positive associations, in women, between trait anxiety with body mass index (BMI) and with kilocalories consumed at the buffet (p=0.005) and percent kilocalories taken in from fat (p=0.006) when the model was adjusted for BMI. In within-pair models, which control for shared familial and genetic factors, this relationship trait anxiety had with the kilocalories from the buffet remained but not its link with BMI. Women with high trait anxiety were observed not to suppress activation by fattening food cues across brain regions associated with satiety perception after eating a standardized meal (based on the fMRI data). This study has evidence to believe that among women, trait anxiety can potentially predispose excess intake of calories through a change in perception of high-calorie environmental food cues, which could place these women with genetic predispositions toward weight gain at risk of obesity. [NPID: stress, anxiety, trait anxiety, buffet, twins, fMRI, food cues, satiety, obesity]

Since the impact of diet on stress reactive systems has not been tested long-term, Shively et al. (2020) fed a proportion of 38 adult, socially-housed, female cynomolgus macaques with the western diet and another with the Mediterranean diet, both for 31 months (which is equivalent to 9 human years) in order to analyze the difference in long-term effects on behavioral and physiological responses to acute (brief social separation) and chronic (social subordination) psychosocial stress. Enhanced stress resilience was observed in the macaques fed the Mediterranean diet relative to those fed the western-style foods, indicated by the brisker and more overt heart rate responses to acute stress, the lower sympathetic activity, quicker recovery, and lower cortisol responses to acute psychological stress and adrenocorticotropin (ACTH) challenge. In addition, the Mediterranean diet appeared to delay the age-related increases in sympathetic activity and cortisol responses to stress. These findings imply that implementing a Mediterranean-like dietary pattern could be a cost-effective intervention on psychological stress, and could potentially promote healthy aging. [NPID: stress, Western-style diet, WS diet, behavior, social separation, social subordination, Mediterranean diet, Med diet, cortisol, healthy aging, aging]

In this 2019 cross-sectional study, a sample of 105 Arabian male medical students (mean age 21) were taken and examined on their dietary patterns in order to determine its association with stress. These future medics studying at Al-Imam Muhammed Ibn Saud Islamic University completed questionnaires to assess their diet. Freshmen were found to experience higher stress levels than sophomores and juniors, while increased stress related to greater consumption of unhealthy foods compared with lower stress status. The likelihood of these students eating unhealthy foods was positively influenced by the spread of fast-food restaurants. Aljaber et al. (2019) demonstrated the importance of stress-reducing interventions to help the students, leading the researchers to propose a way to decrease academic stress, by converting the longitudinal courses to blocks for example. The development of educational programs aimed at promoting healthy eating habits in medical students was also encouraged following these findings. [NPID: stress, Arab, medical student]