The relationship between diet and mental health

Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis

CONTEXT

Vegetarian and vegan diets are increasing in popularity. Although they provide beneficial health effects, they may also lead to nutritional deficiencies. Cognitive impairment and mental health disorders have a high economic burden.

OBJECTIVE

A meta-analysis was conducted to examine the relationship between vegan or vegetarian diets and cognitive and mental health.

DATA SOURCES

PubMed, Scopus, ScienceDirect, and Proquest databases were examined from inception to July 2018.

STUDY SELECTION

Original observational or interventional human studies of vegan/vegetarian diets were selected independently by 2 authors.

DATA EXTRACTION

Raw means and standard deviations were used as continuous outcomes, while numbers of events were used as categorical outcomes.

RESULTS

Of 1249 publications identified, 13 were included, with 17 809 individuals in total. No significant association was found between diet and the continuous depression score, stress, well-being, or cognitive impairment. Vegans/vegetarians were at increased risk for depression (odds ratio = 2.142; 95%CI, 1.105-4.148) and had lower anxiety scores (mean difference = -0.847; 95%CI, -1.677 to -0.018). Heterogeneity was large, and thus subgroup analyses showed numerous differences.

CONCLUSIONS

Vegan or vegetarian diets were related to a higher risk of depression and lower anxiety scores, but no differences for other outcomes were found. Subgroup analyses of anxiety showed a higher risk of anxiety, mainly in participants under 26 years of age and in studies with a higher quality. More studies with better overall quality are needed to make clear positive or negative associations.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42018097204.

Fruit and Vegetable Intake and Mental Health in Adults: A Systematic Review

The role of a properly balanced diet in the prevention and treatment of mental disorders has been suggested, while vegetables and fruits have a high content of nutrients that may be of importance in the case of depressive disorders. The aim of the study was to conduct a systematic review of the observational studies analyzing association between fruit and vegetable intake and mental health in adults. The search adhered to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and the review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42019138148). A search for peer-reviewed observational studies published until June 2019 was performed in PubMed and Web of Science databases, followed by an additional manual search for publications conducted via analyzing the references of the found studies. With respect to the intake of fruit and/or vegetable, studies that assessed the intake of fruits and/or vegetables, or their processed products (e.g., juices), as a measure expressed in grams or as the number of portions were included. Those studies that assessed the general dietary patterns were not included in the present analysis. With respect to mental health, studies that assessed all the aspects of mental health in both healthy participants and subjects with physical health problems were included, but those conducted in groups of patients with intellectual disabilities, dementia, and eating disorders were excluded. To assess bias, the Newcastle-Ottawa Scale (NOS) was applied. A total of 5911 studies were independently extracted by 2 researchers and verified if they met the inclusion criteria using a 2-stage procedure (based on the title, based on the abstract). After reviewing the full text, a total of 61 studies were selected. A narrative synthesis of the findings from the included studies was performed, which was structured around the type of outcome. The studies included mainly focused on depression and depressive symptoms, but also other characteristics ranging from general and mental well-being, quality of life, sleep quality, life satisfaction, flourishing, mood, self-efficacy, curiosity, creativity, optimism, self-esteem, stress, nervousness, or happiness, to anxiety, minor psychiatric disorders, distress, or attempted suicide, were analyzed. The most prominent results indicated that high total intake of fruits and vegetables, and some of their specific subgroups including berries, citrus, and green leafy vegetables, may promote higher levels of optimism and self-efficacy, as well as reduce the level of psychological distress, ambiguity, and cancer fatalism, and protect against depressive symptoms. However, it must be indicated that the studies included were conducted using various methodologies and in different populations, so their results were not always sufficiently comparable, which is a limitation. Taken together, it can be concluded that fruits and/or vegetables, and some of their specific subgroups, as well as processed fruits and vegetables, seems to have a positive influence on mental health, as stated in the vast majority of the included studies. Therefore, the general recommendation to consume at least 5 portions of fruit and vegetables a day may be beneficial also for mental health.

Fruit and vegetable intake as a moderator of the association between depressive symptoms and cigarette smoking

BACKGROUND

Studies have consistently reported associations among depression, cigarette smoking, and fruit and vegetable intake (FVI). This study evaluated FVI as a moderator of the association between depressive symptoms and smoking.

METHODS

The authors analyzed data from the National Longitudinal Survey of Youth 1979: Child and Young Adult. The study sample was adults aged 19-33 years at baseline in the year 2004 from the Young Adult Survey portion. Moderation analyses were performed using the Johnson-Neyman technique to assess whether baseline FVI moderated the association between depressive symptoms and smoking status cross-sectionally and as a predictor of smoking cessation longitudinally at 4-year follow-up.

RESULTS

Cross-sectionally, at lower levels of FVI (<4.9 times/day), there was a significant association between smoking and depressive symptoms (P < .05), but not at higher levels of FVI (≥4.9 times/day; P > .05). Longitudinally, there was an inverse association between depressive symptoms and quitting smoking at FVI <1.2 times/day (P < .05), but there was not a significant association at FVI ≥1.2 times/day (P ≥ .05).

CONCLUSIONS

FVI moderated the association between depressive symptoms and cigarette smoking cross-sectionally and longitudinally. The cross-sectional findings might be partially explained by the longitudinal findings paired with prior research; there might be fewer smokers with high FVI because depressive symptoms are removed as an impediment to cessation. Further experimental research is warranted to test the efficacy of increased FVI as an adjunct to smoking cessation, with a possible mechanism of action being reduced depressive symptoms during quit attempts.

Psychological distress, gender and dietary factors in South Asians: a cross-sectional survey

OBJECTIVE

Psychological distress, defined as symptoms of depression and anxiety, is an increasingly important public health issue in developing countries. Little is known about the extent to which adverse dietary factors are associated with psychological distress in South Asians. Our aim was to compare the associations of diet and psychological distress in men and women in Goa, India.

DESIGN

Cross-sectional study of consecutive attendees in nine urban and rural general practices in Goa, India in 2004-2005. All participants completed an FFQ on their dietary intake in a typical week. Psychological distress was measured using the Kessler Psychological Distress Scale (K10), a WHO-validated screening instrument.

RESULTS

Consecutive attendees (n 1512; 601 men and 911 women) aged 30 to 75 years participated. Moderate and high scores of psychological distress were detected in significantly more women than men (eighty-eight men v. 264 women, unadjusted OR = 0·39; 95 % CI 0·29, 0·52). Those who ate one or more portions of fish weekly had nearly half the prevalence of distress in both sexes (women, OR = 0·52; 95 % CI 0·29, 0·91; men, OR = 0·50; 95 % CI 0·25, 0·99) and this was independent of age, marital status, education, income, religion and living alone.

CONCLUSIONS

Psychological distress is significantly lower with fish intake in both sexes. Further longitudinal work is needed to establish temporal relationships. Addressing psychological distress is becoming an increasingly significant public health priority in both high- and low-income countries.

Stages of change and health-related quality of life among employees of an institution

BACKGROUND

Transtheoretical Model of change has been used successfully in promoting behaviour change.

OBJECTIVE

To examine the relationships between health-related quality of life (HRQoL) scores with the stages of change of adequate physical activity and fruit and vegetables intake.

DESIGN

This was a cross-sectional study conducted among employees of the main campus and Engineering campus of Universiti Sains Malaysia (USM) during October 2009 and March 2010.

MAIN VARIABLES STUDIED

Data on physical activity and fruit and vegetable intake was collected using the WHO STEPS instrument for chronic disease risk factors surveillance. The Short Form-12 health survey (SF-12) was used to gather information on participants' HRQoL. The current stages of change are measured using the measures developed by the Pro-Change Behaviour Systems Incorporation.

STATISTICAL ANALYSIS

One way ANOVA and its non-parametric equivalent Kruskal-Wallis were used to compare the differences between SF-12 scores with the stages of change.

RESULTS

A total of 144 employees were included in this analysis. A large proportion of the participants reported inadequate fruits and vegetable intake (92.3%) and physical activity (84.6%). Mean physical and mental component scores of SF-12 were 50.39 (SD = 7.69) and 49.73 (SD = 8.64) respectively. Overall, there was no statistical significant difference in the SF-12 domains scores with regards to the stages of change for both the risk factors.

CONCLUSIONS

There were some evidence of positive relationship between stages of change of physical activity and fruit and vegetable intake with SF-12 scores. Further studies need to be conducted to confirm this association.