Association between depression and fruit and vegetable consumption among adults in South Asia

Background In recent years there has been a growing research interest regarding the impact of dietary behaviour on mental health outcomes. The present study aimed to investigate the association between fruit and vegetable (F&V) consumption and depression in three south Asian countries- Bangladesh, India and Nepal. Methods Cross-sectional data were obtained from World Health Survey of WHO conducted during 2002–04. In total 14,133 adult subjects (Bangladesh 3262, India 7594, Nepal 3277) aged 18 years and above were included in the study. Outcome variables were Self-Reported Depression (SRD) during last 30 days and 12 months. Multivariable regression methods were used to explore the association between F&V consumption and depression. Results Prevalence of Self-Reported Depression during past 12 months were respectively 39%, 17.7%, and 49.9% for Bangladesh, India and Nepal. In India, those who consumed less than five servings of vegetables were respectively 41% [AOR = 1.41; 95%CI = 0.60-3.33] and 57% [AOR = 1.57; 95%CI = 0.93-2.64] more likely to report severe-extreme and mild-moderate depression during past 30 days compared to those who consumed five servings a day. Regarding fruit consumption, compared to those who consumed five servings a day, the odds of severe-extreme and mild-moderate SRD were respectively 3.5 times [AOR = 3.48; 95%CI = 1.216-10.01] and 45% [AOR = 1.44; 95%CI = 0.89-2.32] higher in Bangladesh, and 2.9 times [AOR = 2.92; 95%CI = 1.12-7.64] and 42% higher [AOR = 1.41; 95%CI = 0.89-2.24] in Nepal compared to those who consumed less than five servings a day during last 30 days. Conclusion Daily intake of less than five servings of F&V was associated with higher odds of depression. Nutrition programs aimed at promoting F&V consumption might prove beneficial to reduce the prevalence of depression in south Asian population. Further studies are required to understand the factors limiting the adequate consumption of F&V.


Background
Depression represents a major public health concern worldwide and it is often referred as the common cold in the field of psychiatry. This analogy may provide a good understanding of the frequency of occurrence, however its significance goes far deeper with repercussions on academic and professional performance, Quality of Life (QoL), familial and Social Well Being (SWB). Global Burden of Disease (GBD) 2010 Study reported a global prevalence of Major Depressive Disorder (MDD) of 4.7% (4.4-5.0%) with an incidence of 3.0% (2.4-3.8%) [1]. Moussavi et al. reported a lifetime prevalence of depression of 15 to 20% globally [2]. Another Global Burden of Disease (GBD) 2010 study reported that MDD ranked 11 th among the leading causes of Disability Adjusted Life Years (DALYs) worldwide in 2010, a 37% increase since 1990 (15 th in 1990) [3]. Worldwide, about 25% of individuals develop one or more mental or behavioral disorders during their lifetime [4]. In 2002, depression was the third leading cause of disease burden (equivalent to 4.3% of all DALYs), and also the leading cause of disability responsible for 13.4% of Years Lived with Disability (YLDs) in women and 8.3% in men [5]. According to the World Health Organization, depression is projected to be a leading cause of disability worldwide by 2020, second only to ischemic health disease [6].
There is a growing volume of research dedicated to investigating the epidemiology and rising prevalence of depression, the risk factors, and devising preventive and intervention measures. Some have attributed the increasing prevalence to the changing lifestyle brought by modernity and to the depressiogenic/stressogenic environment it has brought along e.g. dietary changes, urbanization, social inequality and isolation, loneliness, sedentary lifestyle, sleep-deprivation [7][8][9]. Certain lifestyle related issues and adoption of unhealthy behaviours function as contributing factors to poor physical health outcomes and give rise to higher incidence of psychological disorders [7][8][9][10]. Pharmacological treatments of depressive disorders have experienced remarkable progress over the course of past 4-5 decades and constitutes to be the main therapeutic approach for depression. However, non-pharmacological management (e.g. dietary behaviour, physical activity) of psychological disorders are also gaining increasing attention. For instance, there has been a renewed interest in the potential role of dietary management such as fruit and vegetables consumption in preventing Non-communicable Chronic Disease (NCDs) including mental illnesses [11,12]. According to some estimates, inadequate fruit consumption is the most prominent dietary risk factor for global disease burden and responsible for about 4.9 million (95% CI 3.8-5.9) deaths and 4.2% (95% CI 3.3-5.0) of global DALYs [13].
Fruits and vegetables are regarded as essential components of a healthy diet for their low energy content and rich sources of micronutrients, fiber, and other large number of bioactive compounds with potential effect on brain and overall health [14]. One widely accepted mechanism for higher fruits and vegetables consumption on better mental health is that antioxidants defend against the negative effects of oxidative stress, which is associated with depression [15,16]. Moreover, antioxidants are shown to have beneficial effects on inflammatory markers which are associated with elevated levels of depression [17]. Regular consumption of fruits and vegetables can help body fight against the causative agents and cope up with depressive syndromes. Dietary guidelines by WHO/FAO recommends a minimum of 5 servings (400 g) of F&V/day that provides a reasonable amount of micronutrients which may contribute to favorable cardiometabolic outcomes [18]. However, in many Low and Middle-Income Counties (LMICs) the level of F&V intake is far lower than this level. In South Asia for instance, F&V intake among adults in India and Pakistan was reported at about 100 g per capita per day or less, compared to 300 g in Europe and the USA [19]. Country level data on F&V consumption are not available, however different sources suggest that average number of vegetable servings on the days when vegetable was consumed were of 3-3.4 servings in Matlab, and 1.3-1.5 servings in Vadu, India [19]. A multi-country study reported 74% lower than recommended level of F&V consumption among adult population in India [20]. Though several researches have provided evidence on the role of F&V consumption in the prevention of chronic diseases on South Asian population, there is no study so far conducted in the context of psychological disorders. With an aim to address this gap, we conducted this study exploring the association between the frequency of F&V consumption and Self-Reported Depression. It should be noted that data on dietary pattern and mental illness are very limited in this region. We utilised datasets from the World Health Survey (2002-04) which is the first to provide country representative data on these indicators in South Asia.

The survey
This study is based on data extracted from World Health Survey of WHO conducted between 2002 and 2004 which are available from WHO upon request. The program is operational in 70 countries including four south Asian nations namely Bangladesh, India, Nepal and Sri Lanka. Objectives of the WHO funded survey were to provide reliable, nationally comparable data on a wide range of health and socioeconomic indicators that are necessary for monitoring performance and responsiveness of health systems progress towards public health related goals [21]. The target population were randomly selected male and female adults aged 18 years or over residing in non-institutional settings (e.g. excluding military reservations, or other non-household living arrangements). For those who were in a health institution (e.g. hospital, hospice, nursing home, home for the aged, etc.) at the time of household visit, interview was conducted either in the institution or upon their return to their household if within a period of two weeks from the first visit to the household.
The interviews were done face-to-face in the local language using pencil and paper questionnaires. Each interview lasted for approximately sixty minutes depending on the comprehension and literacy level of the respondent. Interviews were conducted by qualified personnel familiar with the local culture, customs and the language. Multistage cluster sampling method was employed to include eligible individuals and the number of individuals selected were 5924 for Bangladesh (response rate 94%), 9977 for India (response rate 97%), 8818 for Nepal (response rate 98%), 6759 for Sri Lanka (response rate 99%). Further details regarding the survey methods are available elsewhere [22].

Outcome
Self-Reported Depression (SRD) status during last 30 days and 12 months were the outcome variable in this study.
Respondents were asked-During the last 12 months, have you had a period lasting several days when you felt sad, empty or depressed. Self-reported response categories to these question was-1. Yes, 2. No.
For short term depression, the question was-Overall in the last 30 days, how much of a problem did you have with feeling sad, low or depressed? Possible answers to this question were: 1. None 2. Mild 3. Moderate 4. Severe, and 5. Extreme. For regression analysis, the categories were collapsed into three: Not depressed, Mild-Moderate Depression, and Severe-Extreme Depression.
The explanatory variable of primary interest was fruit and vegetable consumption. Respondents were asked: How many servings of fruit do you eat on a typical day?
Answer ranged from 0 to 14 servings a day. As per WHO/FAO recommendation, the cut-off of at least five servings of F&V a day was used, and the following categorisation was used: <5 servings a day/5 servings a day every day/>5 servings a day.
Based on literature review and availability on the datasets, the other explanatory variables included in the study were-Age: 18-29/30-39/40-49/50-59/60+ years; Sex: Female/ Male; Currently married: No/Yes; Educational attainment: Nil/Less than primary school/Primary complete/Secondary complete/High school/equivalent complete/Pre-university/ University; Employment status: Government employee/Private employee/Employer/Unemployed; Smoking habit: Daily/Yes but not daily/Non-smoker; Ever drank alcohol: Yes/No, Satisfaction with health: Very dissatisfied/Dissatisfied/Neither Satisfied nor dissatisfied/Satisfied/ Very Satisfied.

Statistical analysis
Datasets were checked for missing values, outliers and were weighted to ensure the results are representative of the population. Variables were also categorised before analysis. Sample characteristics were analysed through simple descriptive statistics e.g. frequencies and percentages. Cross tabulation was performed to measure the distribution of the sociodemographic variables across the outcome variable and crude prevalence of depression. Significance of group differences (depressed Vs not depressed) for the explanatory variables were tested by chi-square tests and was presented as p-values. Final step was regression analysis that assessed the adjusted associations between depression and F&V consumption. Only the variables that had a p-value below 0.025 in the cross-tabs were selected for the regression analysis [23]. Three separate regression models were run for each country. The outcomes of the regression analysis were reported in terms of adjusted odds ratios (AOR) and corresponding 95% confidence intervals. Analyses were performed with SPSS version 21 and Stata version 12.

Results
Basic socioeconomic and demographic characteristics of the study population are presented in Table 1 Prevalence of self-reported depression and its association with the explanatory variables Table 2 indicates that prevalence of Self-Reported Depression (SRD) was respectively 39%, 17.7%, and 49.9% for Bangladesh, India and Nepal. SRD tended to be more   Those who reported being very satisfied with health and consuming 5 or 5+ servings of fruits and vegetables were less likely to report suffering from depression. Prevalence of SRD in past 30 days was shown in table 3. Nepal had the highest prevalence of severe to extreme SRD (17.2%) and India had the lowest (11.9%). Mild to moderate SRD was most prevalent in Bangladesh (44.7%) followed by Nepal (36.4%) and India (33.3%). Similar to SRD during past 12 months, that during past 30 days were more prevalent among those were elderly, female, currently unmarried, had no formal education and employment, smoked tobacco, drank alcohol and less prevalent among those who reported satisfaction with health and consuming 5/5+ servings of fruits and vegetables every day.

Association between fruit and vegetable consumption and SRD
Results of multivariable regression analysis for the association between frequency of fruit and vegetable consumption during past 12 months and 30 days with SRD were shown in Tables 4 and 5. Results indicate that compared to those who consumed five servings of vegetables per day, those who consumed less than five servings had 51% [AOR = 1.51; 95%CI = 0.82-2.76] higher odds of reporting depression during past 12 months in India. In Bangladesh, consuming more than five servings of vegetables decreased the odds of SDR by 32% [AOR = 0.67; 95%CI = 0.44-1.03]. Compared to those who consumed five servings of fruits per day, the odds of SDR were respectively 86% and 3.1 times higher in Bangladesh and India among those who consumed less than five servings.
Regarding fruit consumption, compared to those who consumed five servings a day, the odds of severeextreme and mild-moderate SDR were respectively 3.

Discussion
Findings indicate that Nepal had the highest rate of SRD both in the past 12 months and 30 days followed by Bangladesh and India. However, prevalence of mildmoderate depression was highest in Bangladesh as more than two-fifth participants reported being depressed during past 30 days compared to about one-third in Nepal. India had the lowest prevalence of depression of any duration. Explanations for this variation is not within the scope of the present study, however the lowest prevalence of depression among Indians could partly be due their better living standard (In terms of HDI) compared to most other south Asian nations. Material standard of living were reported to be associated with poor physical and mental health outcomes [21]. Prevalence of adequate amount (five servings per day) of fruits and vegetable consumption were remarkably low in all three countries. Fruit consumption at five servings/day was highest in India flowed by Nepal and Bangladesh. This could be due the fact that fruit is used as an essential component in traditional festivals and rituals practised by the Hindu communities across India and Nepal. Surprisingly, vegetable consumption (five servings/day) was lowest in India. Despite being a largely vegetarian country and being among the highest F&V producing nation, F&V account for less than one-tenth of total caloric intake among Indians [24]. This is mainly due to higher dependence on cereal diets, and availability issues due to poor preservation and supply chain infrastructure. Low F&V consumption may also be due to the dietary transition and rapid urbanization these countries are experiencing [22]. Over the past two decades, South Asian food intake patterns and dietary composition have undergone remarkable changes marked by a shift from a traditional cereal-and vegetable-based and low-meat diet to a high animal-based and low fruits-and vegetable-based diet [22]. In Bangladesh, consumption of F&V is currently 20% below the recommended daily intake [25]. In a Nepal, different studies have reported that about 66 to 99.2% of the population were not consuming recommended level of F&V [26,27].
Consistent with previous researches, F&V intake was associated with higher prevalence of SRD in our analysis. Though data are not available for south Asian countries, evidence from developed countries indicate a positive dose-response relationship between F&V consumption with the risk of depression [28][29][30]. Among Swiss adults, consuming five servings of F&V a day was associated with lower odds of being highly or moderately distressed than consuming less than that [28]. Cross-sectional studies in the US and Canada also reported positive association between high fruit and vegetable consumption and lower mental distress [29,30]. A recent metaanalysis on ten studies indicated that F&V consumption was inversely associated with the risk of depression [31].

Strengths and limitations
To our knowledge, this is the first study to focus on F&V consumption and depression in South Asian population. Sample size was reasonably good for all three countries and was representative of the population. Therefore, the findings serve equally usefully to both policy makers and public health and nutrition researchers. As both shortterms and long-term depression were included, the findings produced a clearer picture on the magnitude of depression. Using the standard cut-off of five servings a day provides an internationally comparable prevalence of F&V consumption in the population. Despite these contributions, there are some important limitations that need to be considered to interpret the findings. As the survey was cross-sectional in nature, it does not allow making any causal inference of the associations. Also, since the direction of the association is not possible to know, low intake of F&V among subjects with depression could also be a result of reduced appetite. Last but not least, information on F&V intake and depression were self-reported, hence

Conclusion
In conclusion, prevalence of depression was high in all countries and was more prevalent among subjects who reported less than adequate level of F&V intake. An alarmingly large proportion of sample population did not adhere to the recommended amount of F&V consumption. Although the basic therapeutic approach for depression is pharmacological treatment, many clinical psychiatrists consider non-pharmacological approaches as an essential component of treatment. Non-pharmacological interventions such as dietary modification by encouraging higher consumption of F&V should be given more programmatic attention. The widespread production of F&V offers the opportunity for mass intervention of depression. In order to promote F&V consumption at national level, nutrition education and dietary behaviour changing programs can be integrated with community health projects. Addressing the barriers to access to F&V should also be taken into consideration in national food and nutrition security agenda. More in-depth studies are required to understand the barriers to and behavioral factors associated with F&V consumption.