Diet and mood

(2016) This study evaluates whether an enhanced level of psychological well-being directly correlates to the quantity of fruits and vegetables consumed. Food diaries from 2007, 2009 and 2013 were taken from 12,385 Australian adults randomly selected in the "Household, Income, and Labour Dynamics in Australia" Survey (HILDA). A greater consumption of fruit and vegetables was found to have a positive relationship with psychological health, shown by the jump in satisfaction points by consuming 8 added portions a day. These psychological gains were found to equal the happiness achieved by changing from being unemployed to employed.

(2015) Lee et. al (2015) explores changes in mood, cognitive and cardiovascular function in response to a 10-day Mediterranean-style dietary intervention. The foods associated with countries bordering the Mediterranean Sea include legumes, olive oil, fish and are linked to a reduced risk of developing depression. This crossover study randomly divided 24 women into 2 groups differing in diet: one was given a Mediterranean diet for 10 days and the other remained on their regular diet for the same length of time before the diets of both groups were switched to the other group for another 10 days. In this study the Mediterranean diet was found to be a mood enhancer (raised contentment and alertness), improved memory recall and cardiovascular features. These findings were not affected by the order in which diets were adopted, and shows encouraging promise in treating mood disorders long-term.

(2017) Using smartphone-based ecological momentary assessment, this study measured immediate changes in eating happiness levels over a 8 day course. 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.

(2019) Due to the scarcity of studies using this method, Ocean et al. decided to adopt the panel data analytical technique to investigate the relationship between increased consumption of fruits and vegetables and psychological well-being. The same individuals were questioned a total of 3 times between 2010 and 2017 as part of the UK Household Longitudinal Survey. The fixed-effects regression estimates using a reversed form of GHQ-12 demonstrated that as the number and frequency of fruit and vegetable intake increases as did the well-being of the participant. The results suggest that the relationship is robust and the subjective aspect of the study should be negligible. After comparing age with fruit and vegetable consumption, a hump-based relationship was found.

(2015) In this study, eudaemonic well-being and behaviours were measured against fruit and vegetable consumption in young adults. The experiment involved 405 subjects writing an internet daily 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 F&V compared to the days when they didn’t eat as much F&V. While this study suggests increased F&V can improve eudaemonic happiness, creativity and curiosity, there was little evidence of the benefits of eating crisps and sweets.

(2015) The study finds positive links between the ratio of Long-Chain Omega 6 fatty acids (LCn-6) to Long-Chain Omega 3 fatty acids (LCn-3), and low eicosapentaenic acid (EPA) and/or docosahexaenoic acid (DHA) biostasis with the incidence of mood disorders, major depressive disorder and bipolar disorder. This is explained by the implication of LCn-3, EPA and DHA possessing anti-inflammation properties. Therefore, it is predicted that increased intake in LCn-3 could relieve mood disorder through reducing immune-inflammatory signalling.

(2017) The association between fruit and vegetable consumption and incidence of psychological distress was examined by studying 60404 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 the follow-up. Lower prevalence of psychological distress was seen to be associated with increased fruit and vegetable intake even after minimal and full adjustments on sociodemographic and lifestyle risk factors were made. Many of these associations were significant in the medium-level FV consumption but were not found to be significant in the highest FV consumer group in fully adjusted models. The results of this study suggests 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.

(2018) Since polyunsaturated fatty acids (PUFAs) are abundant in the brain and have been linked to anxiety and depression, Larrieu & Laye (2018) analyse the role of the PUFA omega-3 (ω3) series in the prevention and treatment of neuropsychiatric diseases. The review delves into the potential mechanisms of ω3 PUFAs in altering the neurobiological processes leading up to depression and anxiety.

(2018) This study evaluated whether psychological well-being predisposes older adults to eat more fruits and vegetables. The 6565 participants of the English Longitudinal Study of Ageing were examined over a 7 year span to determine their psychological functioning. Boehm focused on 17 items of CASP-19 including pleasure, self-realisation and autonomy. From the initial stages, the men and women 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).

(2019) This review analysed the potential association between vegetable consumption and mental health. Many studies have grouped fruits and vegetables together and examined their psychological effects but in this review, only research with data on solely vegetable intake was included. The total sample size taken from 10 different studies was 33,645. Out of all the healthy non-clinical adults, two thirds reported feeling better on the vegetable only group in relation to depressive symptoms. When the recommended amount of both fruits and vegetables were eaten, psychological well-being improved. However, its efficacy in reducing symptoms of mental health was unclear. This begs the question if there should be more research work undertaken on vegetables alone and its potential role in the treatment of psychological disease.

(2019) Banta et. al. uses 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), lthe following were significantly associated with MPD and SPD: lower consumption of fruits, 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.

(2016) Trans fatty acids (primarily from margarines) and polyunsaturated fatty acids (PUFAs) and their inverse associations on positive affect and positive associations with negative affect were hypothesised in this study. The sample taken from the Adventist Health Study-2 completed a food frequency questionnaire in 2002-2006 before those identified with cardiovascular disease were excluded to create this current study subset of 8771. Those remaining completed the Positive and Negative Affect Schedule (PANAS) in 2006-7, and linear regression analysis was performed (controlling for age, gender, ethnicity, education, body mass index, exercise, sleep, sleep squared, Mediterranean diet, total energy intake and alcohol). The hypothesis was confirmed - increased trans fatty acid intake was linked to more negative affect (p<0.001), while being inversely associated with positive affect (p<0.001). While n-3 PUFAs could not be associated with either positive nor negative affect, the inverse association between the n-6:n-3 PUFA ratio with positive effect suggests that emotional affect can be improved by not only a low trans fat diet but also the right n-6:n-3 PUFA ratio can be beneficial.

This short 2020 article seeks to analyse the complex relationship between food and mental health, answering questions on carbohydrates, dietary patterns, bacteria in the gut and explaining how these factors could be affecting our mood and depressive tendencies. Firth et. al (2020) reveals that healthy eating patterns such as the Mediterranean Diet are associated with reduced risk of depression and better mental well-being compared to the “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 is closely related to one another. 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 even reduce symptoms of depression. It is highlighted also 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 symptoms.

This current study conducted a cross-sectional examination of dietary intake, subjective emotional state, and faecal microbial taxa abundances on 133 adults (ages 25-45) without physician-diagnosed mood disorders in order to explore the relationships among their diets, gastrointestinal microbiota, and mood. Habitual dietary consumption was indicated by the National Cancer Institute’s Diet History Questionnaire II, diet quality was evaluated with the 2010 Healthy Eating Index (HEI), subjective mood state was assessed using the 42-item Depression, Anxiety, and Stress Scale (DASS-42), while fecal DNA was also extracted and a region of the rRNA gene was sequenced and subsequently analysed using QIIME2. The data showed sex-dependent associations among 21 bacteria taxa and DASS-42 scores, including an inverse relationship between anxiety scale scores and Bifidobacterium in females and an inverse relationship between depression scale scores and Lactobacillus in males. Furthermore, the total fruit and dairy components of HEI were negatively associated with Depression and Stress scales, respectively. The findings of this study suggest that gastrointestinal microbes are connected to mood in adults without diagnosed mood disorders and that these relationships differ by sex and are influenced by dietary fibre intake. If future gut-microbiota-brain studies were to incorporate dietary intake into their research they may be able to confirm roles of specific microbes and dietary components in mental health symptoms.

Mood, food, and obesity

A systematic review and meta-analysis of B vitamin supplementation on depressive symptoms, anxiety, and stress: effects on healthy and 'at-risk' individuals

The role of diet and nutrition on mental health and wellbeing

The association between diet and mood: A systematic review of current literature

Fruit and vegetable intake and mental health in adults: A systematic review

(2019) This review investigated the benefits of dietary patterns and consumption of certain foods on depression. The balanced Mediterranean Diet was found to reduce risk of depressive symptoms, while the Western Diet consisting of more saturated fats and refined sugars would more likely lead to depression by disturbing gut microflora and reducing nutrient absorption. Sugar intake itself in sugar-sweetened drinks was positively associated with depression, while the consumption of certain foods such as fish, fruits and vegetables had a beneficial effect on symptoms. The use of the antioxidants green tea polyphenols or isoflavonoid have been shown to reduce signs of depression. The influence of food and nutrients are important factors to consider when clinically treating depression.

Intake of raw fruits and vegetables is associated with better mental health than Intake of processed fruits and vegetables