The Association Between Diet and Mental Health

Abstract

The aim of this study was to investigate the association between diet/nutrition and depression, anxiety and stress accounting for personality traits. First aim was to investigate the relationship between healthy and unhealthy diet and levels of anxiety, depression and stress while accounting for personality traits, secondly to see whether regular eating habits would have an effect on anxiety, depression and stress. Lastly, to look into whether supplementation impacts depression, anxiety and stress symptoms. A survey was conducted and 347 responses were recorded. The Mini International Personality Item Pool (Mini-IPIP), Depression, anxiety and stress scale (DASS-21), Perceived Stress Scale (PSS) and an eating regularity, supplementation, diet adaptation questionnaires were developed for this study. Data was analysed on SPSS and correlation, regression and a Principal Components Analysis (PCA) was run to observe any significant relationships. Hypothesis 1 and 2 were supported, whereas supplementation had no significant relationship with mental health.

The Association Between Diet and Mental Health

What we choose to put into our bodies has the ability to make changes to our mental health. Every individual has a certain diet that they adhere by and this refers to the type and variety of food that they choose to consume. Mental health refers to the way a person thinks, feels and behaves- it is related to psychological and emotional health, this includes depression and anxiety (Glasser, 2003). Depression is defined as a mood disorder that is distinguished by low mood that is recurrent, negative thoughts and actions, a tendency to withdraw from situations, and interferes with everyday life (American Psychiatric Association, 2013). Anxiety is distinguished by more than one factor including nervousness, fear, anxiousness and constant worry impacting thoughts and emotions (American Psychiatric Association, 2013). This report will demonstrate a study that was conducted on the association between diet and mental health- in specific depression and anxiety and whether supplementation has an effect on mental health. It was hypothesized that there would be a negative relationship between diet quality and symptoms of depression and anxiety. It was also hypothesized that more irregular eating behaviors would be associated with increased levels of depression and anxiety. An investigation into the impact of supplementations was conducted to see if there would be any significant findings. This report will include a look into the literature associated with diet and mental health, a method section outlining the process of the study, the results and a discussion about the findings.

Quality and type of food consumed can determine mental health status. A systematic review was conducted to find out whether there was a relationship between diet quality and mental health in children and adolescents. The results showed that there was a significant cross-sectional relationship between unhealthy consumption of food and a decline in mental in children and adolescents (O’neil et al., 2014). Twelve epidemiological studies were looked into and seven of those studies were of high methodological quality, meaning that only seven of those studies were considered good research and well-designed. Similarly, evidence established from two studies conducted by Jacka, Rothon, Taylor, Berk and Stansfeld (2013) and Jacka et al. (2011) demonstrated that an unhealthy diet caused symptoms of depression. The study that was done in the United Kingdom in East London proposed that the results are consistent with other studies (Jacka, Rothon, Taylor, Berk, & Stansfeld, 2013).It is suggested that further intervention studies would need to consider and investigate the effect of avoiding common mental health disorders through changing an individual’s diet (Jacka et al., 2011). This could be because of previous methods that were used that did not allow for interventions in specific to be investigated. These studies demonstrate that if an individual changes the quality and type of food being consumed, there is a good chance of increasing better mental health.

Supplementation use has become very popular worldwide. Tarleton et al. (2017) found that consuming magnesium tablets has a vital role in helping with depression. The evidence suggests that magnesium is only considered effective for mild to moderate depression in adults and it is noted that its effects work rapidly (Tarleton, Littenberg, MacLean, Kennedy, & Daley, 2017). There is no need of supervision from a professional which makes it easier for an individual as the product can be purchased over the counter. Supplementation can be a possible treatment option for people that have depression.

An additional consideration of the Big Five Personality Traits: Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness will be investigated (Zillig, Hemenover, & Dienstbier, 2002). A study looking at three eating surveys to see whether personality traits and eating habits are associated resulted in observations of openness and conscientiousness associated with other health-related aspects (Goldberg & Strycker, 2002).

The first aim of this research was to investigate the association between healthy and unhealthy diet and levels of anxiety, depression and stress while accounting for personality traits, secondly to investigate whether regular eating habits would have an effect on the levels of anxiety, depression and stress. Lastly, to look into whether taking  supplements impacts depression, anxiety and stress symptoms. It was conducted as a cross-sectional correlational study design to determine the association between diet, nutrition and supplementation on mental health.

Method

Participants

432 responses were submitted, 84 cases were removed after visual inspection, a further 3 were removed due to two being fake and one being underage (Qualtrics failed to detect this), leaving a total of 347 responses recorded in the final analysis (97%). Participants needed to be over the age of 18, are required to have basic English skills and are Australian residents. Recruitment was done through the use of social media (Facebook) and flyers were hung around La Trobe University that had a link on it directing to the online survey (see Appendix A). Recruitment also included in-person, which meant having research assistants tell people about the study and ask them whether they would like to participate. Participants were sampled from a wide range of occupations, age groups and educational levels. They had the option of giving their details at the end of the survey for the chance to win one of six $50 gift vouchers. An Ethics approval was completed- the approval number is: HEC18113- low risk study.

Materials

A Qualtrics survey database was used to administer and collect participant responses and data was put through using SPSS v.22 to analyse the data. Table 1 summarises the scales that were used within the study.

Table 1.

Summary Table of the scales used and their Descriptions and Reliability.

Scale	Description of Scale and Reliability Information
Demographic Questionnaire	Included a total of 17 questions asking about background information such as age, gender, living, annual income before tax, education level, general health, occupation, ethnic background, smoking status, height, weight and diagnosis of depression/anxiety.
Mini-IPIP- Mini International Personality Item Pool	Has 20 items measuring an individual’s personality based on the following five traits: Neuroticism, Extraversion, Agreeableness, Conscientiousness, and Openness. The items were scored on a five point Likert scale- 1 being ‘Strongly disagree’ and 5 being ‘Strongly agree’. The higher the score, the more likely an individual has that certain trait. The Internal reliability of the Mini IPIP ranges between α= .62 and α= .78 along all the domains of the personality traits, meaning acceptable internal consistency (Donnellan, Oswald, Baird, & Lucas, 2006).
DASS21- Depression Anxiety Stress Scale	DASS-21 is a short form of the original DASS, consists of a 21-item self-report questionnaire that measures symptoms of depression, anxiety and stress symptoms. Reliabilities and internal consistencies for the DASS-21 resulted in Depression: α= .88 with a confidence interval ranging between .87 and .89, Anxiety: α= .82, CI= .80-.83, Stress: α= .90, CI= .89-.91, and the total scale: α= .93, CI= .93-.94. This implies that the scale has adequate internal consistency and reliability (Henry & Crawford, 2005).
PSS- Perceived Stress Scale	Consisted of 10 questions measuring an individual’s perception of stress in their everyday life. They were on a 5 point Likert scale, ranging from 1 being ‘Never’ and 5 being ‘Very often’. The higher the score, the more stressful the situation or concept is to the individual (S. Cohen, Kamarck, & Mermelstein, 1994). PSS has acceptable internal and test-retest reliability according to studies conducted and correlated such as higher PSS scored related to failure to stop smoking (S. Cohen, Kamarck, & Mermelstein, 1983).
Dietary Supplements Questionnaire	This questionnaire was developed for this study. It measures supplement consumption on a 7-point Likert scale. Answers are either yes or no, and how often they take the supplements ranges from: 1= monthly, 2= weekly, and 3= daily.
Diet Adaptation Questionnaire	A questionnaire developed by the CSRIO that contains 58 items regarding eating habits, type and quality of food consumed and how much/ how often food is eaten. Responses range from 0 being ‘Never’ and 3 being ‘Each day’. The amount of servings ranges from 0 servings to 5 or more.
Eating regularity Questionnaire	A questionnaire developed for this study consisting of an 8-item questionnaire looking at eating regularity. The questionnaire investigates the amount of times an individual may snack, the time they eat lunch and dinner, how often a meal is eaten, the amount of times an individual eats throughout a day, and whether snacks replace main meals. Responses range from ‘Everyday’ to ‘Never’ and ‘Once’ to ‘More than 5 times’.

Procedure

Funding applications and Investigator templates were submitted by research assistants. A Human Ethics application was also submitted and the study received approval. A Qualtrics survey was created and the reason it being Qualtrics is because there is the ability to export the data from Qualtrics to SPSS. A recruitment statement was created (see Appendix B) to post on social media. Before making the survey accessible, research assistants completed the survey themselves to investigate whether there are any errors or whether anything needed to be changed. After changes were made and the survey was finalised, recruitment commenced and it was made accessible for two weeks (5^th September- 19^th September). The study was advertised on social media, in-person, and on flyers around the campuses La Trobe University Bundoora, and La Trobe University Bendigo. The aim was to have at least 400 responses. Before commencing the survey, there is a participant information consent form outlining what the study is about, whether participation is compulsory or not, inclusion and exclusion criteria, what they will be asked to do, the benefits, risks, personal information, change of mind and email and contact number were provided for further details or enquiries about the study. The required time to complete the survey is approximately 30 minutes and upon completion of the survey, there is a chance to enter a draw to win one of six $50 gift vouchers for participating. All data is anonymous. After the survey had closed, all flyers and posts were asked to be taken down due to the link not being open anymore and data analysis commenced.

Data Analysis

The data was cleaned and any missing values were replaced with the average score. 84 of the cases were removed after visual inspection and a further 4 were removed due to three being fake and one being underage (16 years old) which Qualtrics failed to detect this, leaving a percentage of 97% (347) completed responses recorded. Then scores for the Mini IPIP and the PSS were reversed. The amount of data was reduced by using a data reduction process in which new variables for Diet and Nutrition were created by multiplying the frequencies by serves (e.g. How often do you eat fruit? x How many serves? = Fruit (New variable)). The only variable that was left as it is the water variable (how many cups per day?). Then a Principal Components Analysis (PCA) was conducted and new variables were created. Kaiser-Meyer-Olkin (KMO) – .8, which is above .6 indicating that the data set is well-suited for PCA and both KMO and Bartlett’s Test of Sphericity were significant (p = .000). The correlations matrix was investigated and values above .3 were not observed, therefor it is not ideal and a factor analysis should be considered, despite this the analysis was continued as it was not seen as of importance. Frequency of each item was recoded: Never=0 instead of Never= 3. The portion size was also recoded using the transform function on SPSS. Scores were recalculated. After running an analysis to view descriptive information and leaving out alcohol and water, the PCA displayed a pattern matrix. Regression and correlation was analyzed to see if there was a significant relationship between the variables and depression, anxiety and stress.

Results

Data collected through Qualtrics was exported onto SPSS. Outliers within the data were investigated and determined as an accurate representation of the sample of this study. A PCA was conducted, Cronbach’s alpha was calculated to find out the reliability of each subscale and the correlations were looked at too.

Table 2 below presents a summary of the demographics of the study. Participants were mainly female (283, 81.6%) and ages ranged from 18- 77.

Table 2.

Summary of Gender, Age, Education level, Occupation status, and Ethnic Background. 

Demographic	Category	Number (Frequency in %)
Age	18-25	242 (69.7)
	26-40	62 (18.2)
	41+	43 (12.1)
Education Level	Year 10 or below	18 (5.2)
	Year 11 or 12	144 (41.5)
	Diploma	40 (11.5)
	Undergraduate or Post graduate Degree	144 (41.5)
Gender	Male	62 (17.9)
	Female	283 (81.6)
	Other	2 (0.6)
Occupation status	Student	129 (37.2)
	Unemployed	13 (3.7)
	Employed	205 (59.1)
Ethnic Background	Australian	151 (43.5)
	Other	196 (56.4)

Table 3 displays the descriptive and reliability of the scales used within the study. The internal consistency was adequate for the PSS, DASS-21 and the Mini IPIP. Cronbach’s alpha ranged from .78 and .93 for the three scales, which adheres to the recommendation of a maximum alpha value of .90- meaning high validity, internal consistency and reliability (Tavakol & Dennick, 2011).

Table 3.

Summary of the Means, Standard Deviations, the number of items on each subscale and Cronbach’s alpha.

Scale & Subscales	No. of items	M	SD	α
Mini IPIP
Openness	4	3.54	.77790	.692
Conscientiousness	4	3.55	.84958	.730
Extraversion	4	3.19	.88732	.764
Agreeableness	4	4.06	.67968	.680
Neuroticism	4	3.12	.83192	.674
DASS-21
Depression	7	5.26	4.54	.897
Anxiety	7	4.95	4.25	.839
Stress	7	7.42	4.52	.869
PSS	10	18.92	7.07	.907
Eating Regularity Questionnaire	3	12.88	2.26	.459
Dietary Supplement Questionnaire	6	190.20	375.36	.706
Diet/Nutrition	54
Total Healthy	30	6441.89	2593.64	.542
Total Unhealthy	24	1441.27	1180.55	.583

A Pearson and Spearman correlation coefficient were conducted to determine the strength and direction of the relationships between the five personality traits (NE, EX, OP, AG, CO) (see Table 4), depression, anxiety through the DASS, PSS for stress, healthy and unhealthy food, supplements, total vegetables, and magnesium. According to Cohen (1992), an r value of .3 is considered small, .5 = medium, and .7 is a large effect. This means that if two groups means have no differences by .2 standard deviations or more, the difference is considered of little importance, even if it is significant (J. Cohen, 1992).

Table 4.

Summary Table of Correlation Coefficients Between the Five personality traits, PSS, healthy and unhealthy foods, total vegetables, supplements, magnesium and the DASS subscales.

Scale

NE

EX

OP

AG

CO

DA

DD

DS

HE

UH

ER

TV

SU

MA

PSS

NE

–

EX

-.116*

–

OP

-.092

.263**

–

AG

.040

.264**

.224**

–

CO

-.207**

.086

-.047

.096

–

DA

.450**

-.161**

-.015

.050

-.200**

–

DD

.510**

-.198**

-.116*

-.006

-.259**

.668**

–

DS

.588**

-.092

-.017

.083

-.176**

.736**

.710**

–

HE

-.085

.131*

.096

.088

.117*

-.079

-.123*

-.057

–

UH

.086

-.070

-.021

-.019

-.076

.101

.127*

.147**

-.039

–

ER

-.193**

.044

.005

.022

.178**

-.209**

-.296**

-.215**

.347**

-.171**

–

TV

-.092

.107*

.118*

.115*

.114*

-.095

-.180**

-.094

.794**

-.137*

.251**

–

SU

.022

.040

.076

.006

.009

-.019

-.017

.050

.077

-.143**

.041

.120*

–

MA

-.012

.018

.014

.050

.032

-.041

-.082

-.067

.102

-.113*

.013

.144**

.552**

–

PSS

.631**

-.158**

-.104

-.014

-.253**

.623**

.783**

.709**

-.109*

.105

-.306**

-.152**

-.032

-.046

–

Note: NE = Neuroticism; EX = Extraversion; OP = Openness; AG = Agreeableness; CO = Conscientiousness; DA = DASS_Anxiety, DD = DASS_Depression, DS = DASS_Stress, HE = Healthy food, UH = Unhealthy food, ER = Eating regularity, TV = Total vegetables, SU = Supplements, MA = Magnesium, PSS = Perceived Stress.

Individuals that responded high to Neuroticism displayed a positive association with depression, anxiety and stress. Therefore, high neuroticism results in increased symptoms in depression, anxiety and stress. Extraversion was negatively correlated with anxiety and depression implying that individuals whom score high in extraversion have a decrease in depression and anxiety. Eating regularity was positively associated with anxiety, but had a negative relationship with stress and depression. This means that an individual’s anxiety symptoms go up when eating regularly. Whereas, stress and depression increase when an individual does not eat regularly. Lastly, a positive association is observed between unhealthy food and stress, implying that the more unhealthy food consumed, the more likely the person will experience stress.

Two three step hierarchical multiple regressions were conducted with Depression and Anxiety being the dependent variable. The Big Five Personality traits were placed in step 1, Total Perceived Stress Scale was placed in step 2, and Healthy, Unhealthy, Eating regularity and Supplements were placed in step 3. Assumptions were violated due to some of the distributions of the scales were not normal. Transforming the data was not an option as this is common to happen in large samples (Tabachnick & Fidell, 2007). Regression statistics are reported in Table 5 for variables predicting Depression.

Table 5.

Summary of Hierarchical Regression Analysis for Variables predicting Depression.

Variable	β	t	sr2	R	R2	ΔR2	p
Step 1				.326	.316	.326
Neuroticism	.463	9.715	.475				.000**
Extraversion	-.140	-2.869	-.157				.004**
Openness	-.042	-.863	-.048				.389
Agreeableness	.029	.606	.034				.545
Conscientiousness	-.172	-3.631	-.198				.000**
Step 2				.584	.576	.257
Neuroticism	.035	.731	.041				.465
Extraversion	-.091	-2.347	-.130				.020*
Openness	-.016	-.421	-.023				.674
Agreeableness	.040	1.069	.059				.286
Conscientiousness	-.103	-2.727	-.150				.007
TotalPSS	.686	14.130	.618				.000**
Step 3				.589	.576	.005
Neuroticism	.032	.666	.037				.506
Extraversion	-.092	-2.387	-.132				.018*
Openness	-.020	-.513	-.029				.608
Agreeableness	.045	1.187	.066				.236
Conscientiousness	-.097	-2.547	-.141				.011*
TotalPSS	.669	13.446	.601				.000**
Healthy	.018	.469	.026				.639
Unhealthy	.034	.905	.051				.366
Eating Regularity	-.066	-1.632	-.091				.104
Supplements	.013	.348	.019				.728

The hierarchical multiple regression at Step 1 demonstrated that Neuroticism, Extraversion, and Conscientiousness contributed significantly to the regression model, F (5, 31) = 31.40, p < .05, and accounted for 31.6% of variation in Depression. In Step 2, the TotalPSS was added and variables explained 57.6% variance. Step 3 had Healthy, Unhealthy, Eating regularity and Supplements which resulted in 57.6% of variance explained. Predictors that made a unique contribution to depression are Neuroticism, Extraversion, Conscientiousness, and TotalPSS. Table 6 will explore variables predicting Anxiety.

Table 6.

Summary of Hierarchical Regression Analysis for Variables predicting Anxiety.

Variable	β	t	sr2	R	R2	ΔR2	p
Step 1				.253	.242	.253
Neuroticism	.439	8.757	.437				.000**
Extraversion	-.137	-2.655	-.146				.008**
Openness	.047	.914	.051				.361
Agreeableness	.042	.838	.046				.403
Conscientiousness	-.098	-1.962	-.108				.051
Step 2				.391	.380	.138
Neuroticism	.126	2.164	.120				.031*
Extraversion	-.100	-2.148	-.119				.032*
Openness	.065	1.418	.079				.157
Agreeableness	.051	1.108	.062				.269
Conscientiousness	-.047	-1.034	-.057				.302
TotalPSS	.502	8.557	.430				.000**
Step 3				.394	.375	.003
Neuroticism	.120	2.039	.113				.042*
Extraversion	-.102	-2.175	-.121				.030*
Openness	.063	1.349	.075				.178
Agreeableness	.052	1.129	.063				.260
Conscientiousness	-.046	-.990	-.055				.323
TotalPSS	.497	8.219	.418				.000**
Healthy	.007	.139	.008				.889
Unhealthy	.002	.043	.002				.966
Eating Regularity	-.036	-.736	-.041				.462
Supplements	.047	1.064	.059				.288

The hierarchical regression displayed in Table 5 shows the variables and their contribution to the regression model, F (5, 22) = 22, p < .05. Step 1 accounted for 24.2%, Step 2: 38% and Step 3; 37.5% of the explained variance. When all variables were added within the last stage, Openness, Agreeableness, Conscientiousness, Healthy, Unhealthy, Eating regularity and supplements had no significance towards Anxiety. Whereas, Neuroticism, Extraversion, and TotalPSS were significant predictors of Anxiety.

Discussion

The first aim of this study was to investigate the association between healthy and unhealthy diet and levels of anxiety and depression and stress while accounting for personality traits. Secondly to investigate whether regular eating habits would have an effect on the levels of anxiety and depression and stress. Lastly, to look into whether taking supplements impacts depression, anxiety and stress symptoms. It was conducted as a cross-sectional correlational study design to determine the association between diet, nutrition and supplementation on mental health. The first hypothesis was supported as an unhealthy diet was associated with an increase in depression, anxiety and stress. The second hypothesis was also supported as irregular eating habits was associated with heightened stress symptoms. The last hypothesis was not supported as supplementation did not have any significant relationships with the variables.

Some of the findings are consistent with past studies by O’neil et al. (2014), who observed that there was a decline in mental health when individuals consumed unhealthy foods. This is the same as what had been discovered within this study- a significant relationship was seen between unhealthy foods and an increase in depression, anxiety and stress. Despite observing no association between supplementation and mental health, magnesium was conducted within the correlation analysis and was not consistent with the findings of another study. Tarleton et al. (2017) stated that magnesium can be effective for mild-moderate depression and works rapidly. Whereas, this study found no associations with magnesium and mental health. Results were consistent with another study that looked at nutritional behaviour and stress and depressive symptoms (El Ansari, Adetunji, & Oskrochi, 2014). Results were consistent with another study that looked at nutritional behaviour and stress and depressive symptoms. As anticipated, the same relationship between unhealthy food and stress/depressive symptoms were observed in both studies. A study looking into a similar age group of 18-89 years of age and the correlation between diet and personality traits displays consistency with the current study (Mõttus et al., 2012). Mõttus et al. (2012) discovered that an increased score in diet factor had a relationship with lower Neuroticism, similarly, this study found that there was a negative correlation between Neuroticism and eating regularity. Studies that associate stress with unhealthy dietary patterns support the outcomes of this study. A healthy eating program with exercise or stress-management can result in assisting individuals with high stress (Gonzalez & Miranda-Massari, 2014).

Limitations within this study included using non-validated scales, a scale that was based off something that was already published. Strengths include: a large sample size that consisted of different backgrounds, ages and ethnicities, the inclusion of personality and nutritional scales, participants were free to complete the survey wherever and whenever they wanted, it was anonymous. Weaknesses include: some participants did not take the survey seriously, missing data, unfinished surveys, study can be a little difficult to replicate.

It would be suggested that in the next study, a reduced number of variables are used, as it makes it less confusing and keeps the study focused on one outcome. It would be a good idea to consider looking for validated scales to assess eating behaviour; such as the Eating Behaviour Rating Scale (EBRS) (Wilson, Touyz, Dunn, & Beumont, 1989). This scale can measure more than one aspect, therefore will cut back on the amount of variables (Tully, Matrakas, Muir, & Musallam, 1997). The next question that should be investigated is whether a combination of healthy food and exercise long-term has an association with depression, anxiety and stress.

As discussed within the previous studies, findings for associations between unhealthy food and mental health with the accountance for personality traits are consistent, whereas, supplementation had no association with mental health. Two of the hypothesis were supported and the results detailed significant findings for depression, stress and anxiety. This report provides evidence for the relationships observed between diet/nutrition and mental health with the accountance of personality traits.

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