Diet and Stress

Since it is not known whether the Mediterranean diet can reverse the increased inflammation induced by stress, this 2018 study examined the two associations - between cortisol with inflammation, and cortisol with the adolescent Mediterranean diet score (aMDS) - before testing whether aMDS associates with cortisol levels and inflammation, and whether inflammation can be reduced by aMDS. The aMDS of the 242 adolescent participants (12.5-17.5 years old) was derived from their salivary cortisol levels, blood results and 2-day 24-h dietary recall. Several relationships involving cortisol were determined, including its inverse correlation with adherence to the Mediterranean Diet (B = -1.023, p = 0.002), and association with elevated tumor necrosis factor (TNF-α B = 11.887, p = 0.001) when adjusted for age, gender, parental education and body mass index (although this became insignificant when aMDS was included in the model). Moreover, when comparing lower and higher aMDS groups, the cortisol-TNF-α interaction was only seen in the lower aMDS group. The concentrations of TNF-α and interleukins (IL) IL-1, IL-2, IL-6 were also found to be lower in individuals highly adherent to the aMDS, compared with those who did not adhere to the diet score. These findings suggest that adherence to the Mediterranean diet may counteract the stress-induced alterations in inflammatory markers, which could ultimately lower prevalence rates of mental disorders.

In this 2019 preclinical study, juvenile rats were repeatedly placed under social instability stress, modifying its cognitive behaviors and plasticity markers in the brain, before being fed a diet rich in ω-3 polyunsaturated fatty acids eicosapentaenoic acid, docosahexaenoic acid, and docosapentaenoic acid and vitamin A for a prolonged period of time, to determine the preventative effects of this diet. The difference in performance in the emotional and reference memory tests between the stressed rats fed the enriched diet and the non-stressed rodents was apparent, indicating positive impact of fatty acids and vitamin A on cognitive memory damage. This diet in question also normalized the composition of the microbiota in the stressed rats, and reversed the decreased brain-derived neurotrophic factor expression in their hippocampus. The neurochemical and behavioral changes induced by stress, as well as the protective influence of the enriched diet, could be observed throughout adulthood, long after stress exposure. Provensi et al. (2019) have provided strong evidence that nutritional components can ameliorate stress-related behaviors and associated neurochemical and microbiota changes, and could play an important role in this field of nutritional neuropsychopharmacology.

Since the dramatically increasing perceived loneliness among adolescents are linked with high stress levels and dysfunctional lifestyles, which are strongly influenced by eating habits, Ferrer-Cascales et al. (2018) analyzed the relationship between perceived loneliness, stress, dietary habits and adherence to the Mediterranean diet (MD) among 527 Spanish adolescents. Greater perceived loneliness and stress levels were significantly associated with lower MD adherence. It was also highlighted that dietary patterns were poorer among those adolescents with greater perceived loneliness, compared with those with low levels of perceived loneliness. Moreover, mediation analyses revealed an indirect effect of the loneliness on adherence to the MD through the mediation effect of stress. This study suggests poorer adherence to a healthy dietary pattern such as MD may play an influential role in the association between loneliness and health deterioration.

Using the data from the University of Newcastle Student Healthy Lifestyle Survey 2017, Whatnall et al. (2019) investigated the association between psychological stress and resilience with dietary intake among Australian university students. Psychological stress was assessed using the Kessler Scale, resilience was determined by Brief Resilience Scale, while a series of short direct questions allowed the collection of dietary information. Multivariate linear regression analysis was performed on 2710 subjects (average age 26.9). In the adjusted models, lower psychological stress and higher resilience were found to be associated with higher fruit and vegetable servings per day, more frequent breakfast consumption, and less frequent soft drink and takeaway food consumption. Diet may play a function in regulating psychological distress and resilience.

This 2019 study aimed to identify the relationship between physical activity (determined by PAQ-A), adherence to the Mediterranean diet (MD; assessed using KIDMED), and academic stress (measured using the Scale of Academic Stress) among a sample of 515 university students. Chacón-Cuberos et al. (2019) discovered that women experienced greater levels of academic stress, especially with respect to communicating their own ideas and their academic obligations. Students in the overweight or underweight class also suffered from high levels of stress, while those less adherent to the MD scored higher for stress associated with conveying their own ideas. Physical activity could not be linked with academic stress, and nor could diet quality after controlling for sex and BMI in the regression model. Although a connection between diet quality and stress cannot be claimed, stress was associated with gender and poorer health - considering the link with being overweight.

Hueston et al. (2017) believe that adolescence is the critical stage of life at which the effect of stressor exposure on hippocampal neurogenesis and cognitive function should be tested since this is the period in which the hippocampus matures and neurogenesis is increased. It is also a particularly stressful time and stress is detrimental to neurogenesis, and can potentially induce long-lasting effects reflected by changes in behavior, neural plasticity and cognitive ability. Diet or exercise-related interventions can possibly counteract the stress-induced alterations, and can promote positive behavioral alterations in adolescence. This review considers the acute and long-term impact of stress on hippocampal neurogenesis and cognition during this important period, while also taking into account the changes in stress response and pubertal hormones that may consequently influence adulthood. The theory is that adolescence is the optimal time to encourage a healthy lifestyle to protect against the impacts of stress and to promote positive and long-lasting effects on hippocampal neurogenesis. Hopefully future studies can elucidate the susceptibility of the adolescent hippocampus to the likes of stress, diet and exercise, and will be able to explain the consequential cognitive effects.

In this 2016 study, adolescent Lewis rats (28 days postnatal) were given unrestricted access to either a Western-like Diet (41.4% kcal from fat) or the control diet (16.5% kcal from fat) for 8 weeks, before being exposed to a cat odor threat (to induce psychological trauma), in order to test if an obesogenic Western-like high-fat diet (WD) pre-disposes rats to post-traumatic stress responsivity. One week into encountering stress, increased anxiety-like behavior was evident in the rats fed on the WD, compared with those on the control diet (indicated by the elevated plus maze and the open field test). The high-fat diet was also associated with significant hippocampal atrophy (20% reduction) and lateral ventricular enlargement (50% increase), observed in the magnetic resonance imaging results. As well as these volumetric disturbances, leptin and FK506-binding protein 51 (FKBP51) levels were elevated, while hippocampal blood vessel density was reduced. Asymmetric structural vulnerabilities to the WD were discovered, particularly in the ventral and left hippocampus and lateral ventricle. This study demonstrates that WD consumption during adolescence influences key substrates implicated in post-traumatic stress disorder. It is important to develop our knowledge on WD’s impact on a person’s course of development since susceptibility to stress translates to greater vulnerability to neuropsychiatric disorders.

This 2018 prospective study recruited 264 pre-college participants to assess the sex differences in their stress, emotional eating, tendency to overeat, and restrained eating behavior examined 1 month before college starts, and to investigate whether there are correlations between these psycho-behavioral constructs with the subjects’ anthropometrics and adiposity at the start of college, and with weight gain during the first semester. The Three Factor Eating Questionnaire (TFEQ), Satter Eating Competence Inventory, and Perceived Stress Scale (PSS) were administered a month before first semester, while dual energy X-ray absorptiometry (DXA) at the start of college provided data on body composition and the students’ anthropometric measurements (weight, height, waist circumference [WC]) were taken at the beginning and at the end of the first semester. Hootman et al. (2018) gathered baseline data on 241 respondents (91%) and successfully followed up on 173 participants (66%). Sex-adjusted linear regression models revealed a positive correlation between TFEQ disinhibited and emotional (DE; EE) eating sub-scales at baseline with baseline weight (P = 0.003 for DE, P = 0.014 for EE), body mass index (BMI, P = 0.002 for DE, P = 0.001 for EE), WC (P = 0.004 for DE, P = 0.006 for EE) and DXA fat mass index (P = 0.023 for DE, P = 0.014 for EE). Interestingly, increased baseline PSS was linked with greater weight changes in the first semester (Pinteraction = 0.0268) and with larger WC (P=0.0017) among males. The findings of this study suggest that college freshmen showing signs of susceptibility to overeat in response to external cues and emotions were more likely to be heavier and have increased BMI and WC at the start of college, while males with elevated levels of perceived stress at college entrance gained significantly more weight in the first semester.

The objective of this 2020 study was to explore the interaction between the perceived stress levels of Korean college students with their level of physical activity and dietary behaviors. Questionnaires were distributed to students on campus, while the 10-item Perceived Stress Scale (PSS-10) was employed to assess the degree of stress perceived. Demographic characteristics were also utilized to determine its influence on the students’ dietary behaviors. Regarding demographics, the eating behaviors and physical activities of the subjects were found to vary by sex, academic year, and residence type. But there were significant differences in dietary behaviors between participants with low and high levels of perceived stress. For example, those with high perceived stress ate more ready-prepared meals (p<0.001). Choi (2020) has conducted a study that has demonstrated the need for stress management in college, and that supports the provision of programs capable of fostering healthy dietary behaviors in students, especially in first year.

Since the studies linking perceived stress with dietary choices included mostly white, female samples, this 2016 study recruited a diverse population of both male and female college freshmen (n=613) and conducted an online survey evaluating ability to manage stress, perceived stress, and their consumption of various food types in the past week. The purpose was to investigate this association between perceived stress and food choices among young college students, and to analyze whether perceived ability to manage stress plays a modulatory role in this relationship. The results showed that greater levels of stress were perceived by those individuals that consumed more soda, coffee, energy drinks, salty snacks, frozen food, and fast food in the past week (p<0.05). Moreover, freshmen that reported low ability to manage stress ate larger amounts of sweet snacks, implying that perceived stress management modulates the relationship between stress and sweet snack consumption. This study claims increased stress may be related to poor dietary decisions, while low ability to deal with stress may worsen the interaction between stress and diet. Errisuriz et al. (2016) encourages college nutrition education programs to consider promoting effective stress management techniques to help students handle heightened stress levels.

Begdache et al. (2019) states that diet may impact mental health in different ways in young adults and mature adults since full maturation of the brain is thought to be achieved at the age of 30. This study investigated the relationship between mental distress with exercise and dietary consumption and practices, and compared the differences between young adults (YA) aged 18-29 and matured adults (MA) aged 30 years and above. Additionally the researchers aimed to find out whether mental health supports exercising and healthy eating and practices. The data was collected by distributing an anonymous online survey on social media platforms. The mood of young adults appeared to depend on foods that increases availability of neurotransmitter precursors and concentrations in the brain such as frequent meat consumption and exercise, while matured adults’ mood were greatly influenced by foods such as fruits that provide antioxidants and by abstaining from foods that inappropriately activates the sympathetic nervous system (e.g. coffee, high glycemic index, and skipping breakfast). These findings may indicate that diets require adjustments as people’s brains start to mature and undergo age-related morphological and functional alterations.

Unhealthy eating and academic stress: The moderating effect of eating style and BMI