Diet and Mood

Conner et al. (2020) state that fruits and vegetables containing high concentration of vitamin C have been linked to greater feelings of vitality but rarely has it been studied in randomised controlled trials. This is why Conner and her team of researchers took 167 young adults (61.1% female, aged 18-35) with vitamin C levels of less than 40 micromoles per liter in the blood and randomly assigned them into one of three intervention conditions including, kiwifruit (given 2 SunGold™ kiwifruits to eat every day), vitamin C (250mg tablet daily), and placebo (involving taking 1 tablet daily). The trial consisted of a two-week lead-in, four-week intervention, and two-week washout, and its purpose was to measure the effect of eating the kiwifruit (a vitamin C-rich food) on the participants’ vitality and to find out whether these effects are driven by vitamin C. Questionnaires on vitality and plasma vitamin C were undertaken every 14 days while sleep quality and physical activity was also self-reported every couple of days through smartphone surveys. The trial found vitamin C levels reached saturation levels within two weeks for both the kiwifruit and vitamin C groups. The kiwifruit-consuming subjects improved in mood and well-being during the 4-week intervention period, and these effects were sustained during washout. In the vitamin C tablet group, less fatigue and enhanced well-being were observed but only in those with consistently low vitamin C levels during the lead-in. The three-day food diaries taken also uncovered a reduction in fat intake by the kiwifruit group during the intervention period. No changes in plasma vitamin C status or vitality were found in the placebo group. The effects of these interventions remained significant after adjustments for age and ethnicity were made, and were not explained by sleep quality, physical activity, BMI, or dietary patterns like fat intake. Since kiwifruit consumption correlated with increased vitality in adults with low vitamin C status, a similar but not identical impact to that of vitamin C tablets, these findings suggest that the additional properties of kiwifruit may contribute to improved vitality. [NPID: mood, fruits, vegetables, vitamin C, kiwi, vitality]

Using smartphone-based ecological momentary assessment, this 2017 study measured immediate changes in eating happiness levels over eight days. 14 different food types were investigated in this study, including healthy options such as vegetables and high-caloric foods such as sweets. Contrary to popular belief that high-caloric foods elicit happiness and counter negative moods, there were surprisingly comparable results between sweets and healthier foods, and between dinner and snacking. Vegetables had the most profound positive impact on eating-induced satisfaction over the course of the study. [NPID: mood, happiness, vegetables, well-being]

In this 2015 study, eudaemonic well-being and behaviours were measured against fruit and vegetable (FV) consumption in young adults. The experiment involved 405 subjects writing a daily internet diary noting any intake of crisps, sweets, fruits, and vegetables. Greater average eudaemonic well-being, increase in creativity, and intensity in curiosity were seen in those young adults who ate more fruits and vegetables than those consuming less, and on days when participants ate more FV compared to the days when they didn’t eat as much FV. While this study suggests increased FV can improve eudaemonic happiness, creativity and curiosity, there was little evidence of the benefits of eating crisps and sweets. [NPID: mood, happiness, vegetables, fruit, eudaemonic well-being, creativity, curiosity]

This 2017 study examined the association between fruit and vegetable consumption and incidence of psychological distress. It examined 60,404 Australian adults aged 45 and over using the validated Kessler Psychological Distress Scale (K10) to assess psychological distress (indicated by high K10 scores >22) and a short validated questioning system to determine their fruit and vegetable (FV) intake. Participants were examined in 2006-2008 and in 2010 for a follow-up. Lower prevalence of psychological distress was associated with increased FV intake even after both minimal and full adjustments on sociodemographic and lifestyle risk factors. Many of these associations were significant in the medium-level FV consumption but not significant in the highest FV consumer group in fully adjusted models. The results of this study suggest that increasing dietary intake of fruits and vegetables in middle-aged and older adults may help reduce chances of psychological distress, although more research is encouraged to find the optimal quantity. [NPID: mood, happiness, well-being, fruit, vegetables, psychological distress]

This 2018 study evaluated whether psychological well-being predisposes older adults to eat more fruits and vegetables. The 6,565 participants of the English Longitudinal Study of Ageing were examined over a seven year span to determine their psychological functioning. Boehm (2018) focused on 17 items of CASP-19 including pleasure, self-realisation, and autonomy. From the initial stages, the participants with a greater sense of well-being were shown to eat more fruits and vegetables. It was also shown that these individuals who started the study with a greater feeling of satisfaction would go on to consume fruits and vegetables for longer over the 7 years (11% reduced risk of dropping below the recommended levels during follow-up). [NPID: mood, happiness, well-being, fruits, vegetables, psychological functioning, pleasure, self-realisation, autonomy]

Banta et al. (2019) used the California Health Interview Survey (representing 27.7 million adults’ answers annually) stretching from 2005-2015 to explore the relationship between mental health and dietary consumption. Kessler-6 scores allowed categorisation of the giant cohort into no/low (NLPD), moderate (MPD) and serious psychological distress (SPD). 13.2% of the population studied were found to have MPD, and 3.7% had SPD. After adjusting for a range of factors (including BMI, geography, year, gender, age, race, education, marital status and poverty), the following were significantly associated with MPD and SPD: lower consumption of fruits and vegetables, and increased intake of french fries, fast food, soda, and variance-adjusted daily teaspoons of sugar. In this study, the trends all pointed to the risk of experiencing MPD or SPD rising in individuals who consume unhealthy foods. [NPID: mood, happiness, well-being, psychological distress, fruits, vegetables]

This short 2020 article sought to analyse the complex relationship between food and mental health, answering questions on carbohydrates, dietary patterns, and bacteria in the gut, and explaining how these factors could be affecting our mood and depressive tendencies. Firth et al. (2020) state that healthy eating patterns such as the Mediterranean Diet are associated with reduced risk of depression and better mental well-being compared to “unhealthy” eating patterns, namely the Western diet. This article links certain foods and eating patterns with glycaemia (concentration of sugars in your body), immune activation and responses, and the gut microbiome to provide insight into how food and mood are closely related. In addition to physical health risks, diets with a high glycaemic index (eg. diets containing high amounts of refined carbohydrates and sugars) are found to be associated with depressive symptoms. High-calorie meals rich in saturated fat appear to stimulate immune activation and inflammation, which is the proposed mechanism by which the Western diet may have detrimental effects on the brain, including cognitive decline, hippocampal dysfunction, and damage to the blood-brain barrier. Moreover, ingestion of probiotics, which theoretically target the gut microbiome, can alter the brain’s response to a task that requires emotional attention and may reduce symptoms of depression. It is highlighted that more research into the complex pathways through which diet and nutrition can influence the brain is required, particularly interventional research investigating if, how, and when dietary interventions can be used to prevent mental illness or reduce its symptoms. [NPID: mood, happiness, well-being, psychological distress, gut microbiota, depression, mediterranean diet, glycaemia, immune system, gut microbiome, microbiome, hippocampus]

In this 2017 editorial, the aim was to set the scale of the mental illness problem into context while presenting recent evidence linking nutrition to psychological outcomes. Owen and Corfe (2017) wrote that the intent of the 2016 Nutrition Society Winter Meeting, "Diet, nutrition and mental health and wellbeing," was to review where the evidence was strong, where the data was lacking, and to discuss findings with others in the communities working in this area of research. This meeting, as well as the present research in the field, led Owen and Corfe (2017) to theorize that even dietary-based interventions with relatively small effect sizes may significantly reduce the disease burden of mental and neurological diseases. [NPID: mood, happiness, well-being, psychological distress, diet, nutrition, mental health]

This 2014 article describes the complex nature of food consumption and its link with mood and brain signalling, while also touching on the sensations of reward and gratification associated with eating certain foods — the dangerous sequence of biological events that overrides an individual's satiety and hunger signals. This constant search for dopamine, the chemical that activates reward and pleasure centers in the brain, can often lead to overeating and morbid obesity, which in addition stem from many biological factors engaging both central and peripheral systems in a bi-directional manner involving mood and emotions. Overeating and obesity can even result from the changes in food choice and consumption levels induced by altered mood and emotional eating. [NPID: mood, happiness, well-being, psychological distress, brain signaling, reward, gratification, satiety, dopamine, obesity, emotional eating]

This 2020 systematic review was conducted to evaluate the relationship between fruit and vegetable intake and mental health in adults, using peer-reviewed observational studies found on either PubMed or Web of Science databases. Further searches were performed manually through inspection of references from the included studies, which increased the number of included studies for the narrative synthesis of findings to 61. The majority of studies were centered around depression and depressive symptoms, although a range of characteristics were assessed overall, from quality of life to attempted suicide. Głąbska et al. (2020) highlight a particular set of findings that indicate greater overall consumption of vegetables and fruits, as well as some subgroups (berries, citrus, and green leafy vegetables) may increase optimism and self-efficacy, while reducing psychological distress, cancer fatalism, ambiguity, and contributing to the prevention of depressive symptoms. It was difficult to compare the findings of all the studies given the variations in methodologies and samples used, which was a limitation, but the review as a whole concluded that fruits and vegetables, processed and natural, as well as their specific subgroups, may elicit positive effects on mental health. The authors advised to consume at least 5 selections of fruit and vegetables daily to improve mental health. [NPID: mood, happiness, well-being, fruit, vegetables, depression, suicide, optimism, self-efficacy, psychological distress, cancer]

In this study, Firth et al. (2020) sought to understand the dynamic between diet and mental health, in particular which specific foods and dietary patterns are related to mental health conditions. The most common of these mental health conditions are depression and anxiety, which affect a vast percentage of people both in their functioning and health. New approaches are needed to better manage clinically diagnosed and subclinical depression and anxiety. Diet-related studies over the last few years have linked specific dietary patterns such as Mediterranean or healthy, and the high consumption of fruits, vegetables, nuts, and legumes, and moderate intake poultry, eggs, and dairy products, with reducing risk of developing depression. But there are other factors to consider when analyzing diet’s relationship with mental health, such as barriers to maintaining a favourable diet (finances, side effects of medications, and other environmental factors). Humans can also make different food choices based on their temporary psychological state — eating “comfort foods” at periods of low mood, for example. This review discusses this important but complex, multidirectional relationship between diet and mental health. [NPID: mood, happiness, well-being, depression, anxiety, mediterranean diet, comfort food]

Here, Liao et al. (2018) examines the interaction between high-fat, high-sugar (HFHS) foods, and fruit and vegetable (FV) consumption with affective states (the underlying experience of feeling, emotion or mood) among women. The 202 female participants’ levels of HFHS foods and fruit and vegetable intake in the previous 2 hours was reported as well as their current affective states across 1 week. It was later revealed that fruit and vegetable consumption over the previous 2 hours positively correlated with the feeling of happiness. Conversely, higher average sadness was observed among individuals who either ate more HFHS foods or less fruits and vegetables than others in the study. The overweight/obese women who ate high-fat and high-sugar foods more frequently also experienced greater stress on average when compared to the normal-weight ladies. Thus, this relationship between HFHS food consumption and stress may be stronger in overweight and obese females than normal weight women. [NPID: mood, high-fat high-sugar foods, HFHS, fruit, vegetables, affect, obesity]