New research from the Canadian Longitudinal Study on Aging shows that adults who have low fruit and vegetable intakes have a higher likelihood of being diagnosed with an anxiety disorder.
“For those who consumed less than 3 sources of fruits and vegetables daily, there was at least at 24% higher odds of anxiety disorder diagnosis,” says study lead Karen Davison, health science faculty member, nutrition informatics lab director at Kwantlen Polytechnic University, (KPU) and North American Primary Care Research Group Fellow.
“This may also partly explain the findings associated with body composition measures. As levels of total body fat increased beyond 36%, the likelihood of anxiety disorder was increased by more than 70%,” states co-author Jose Mora-Almanza, a Mitacs Globalink Intern who worked with the study at KPU.
“Increased body fat may be linked to greater inflammation. Emerging research suggests that some anxiety disorders can be linked to inflammation,” says Davison.
Other factors associated with anxiety disorders among mid-age and older Canadians
In addition to diet and body composition measures, the prevalence of anxiety disorders also differed by gender, marital status, income, immigrant status and several health issues.
One in nine women had an anxiety disorder compared to one in fifteen men.
“Our findings are in keeping with previous research which has also indicated that women are more vulnerable to anxiety disorders than men,” says co-author Karen Kobayashi, Professor in the Department of Sociology and a Research Affiliate at the Institute on Aging & Lifelong Health at the University of Victoria.
The prevalence of anxiety disorders among those who had always been single (13.9%) was much higher than among those who were living with a partner (7.8%).
Approximately one in five respondents with household incomes under $20,000 per year had anxiety disorders, more than double the prevalence of their richer peers.
“We were not surprised to find that those in poverty had such a high prevalence of anxiety disorders; struggling to afford basics such as food and housing causes relentless stress and is inherently anxiety inducing,” says co-author Hongmei Tong, Assistant Professor of Social Work at MacEwan University in Edmonton.
Individuals with three or more health conditions had fivefold the prevalence of anxiety disorders in comparison to those with no chronic conditions (16.4% vs 3%).
Those in chronic pain had double the prevalence of anxiety disorders in comparisons to those who were free of pain.
“Chronic pain and multiple health conditions make life very unpredictable and can be anxiety producing. One never knows whether health problems will interfere with work or family responsibilities and many activities become more challenging and time consuming,” says co-author Shen (Lamson) Lin, a doctoral student at University of Toronto’s Factor-Inwentash Faculty of Social Work (FIFSW).
Immigrants to Canada had a lower prevalence of anxiety disorders compared to their peers born in Canada (6.4% vs 9.3%).
“Immigrants may face a myriad of challenges associated with resettling in a new country, including language barriers, poverty, difficulties in getting qualifications recognized, and limited social support, so it seems counter-intuitive that they should have a lower likelihood of anxiety disorders than those born in Canada.
It may be that potential immigrants with anxiety disorders would find the challenges of relocation too anxiety-inducing and would therefore not choose to immigrate, so there is a ‘self-selection’ for those with lower anxiety,” says senior author, Esme Fuller-Thomson, professor at FIFSW and director of the Institute for Life Course & Aging. Fuller-Thomson is also cross-appointed to the Department of Family and Community Medicine and the Faculty of Nursing.
“For those who consumed less than 3 sources of fruits and vegetables daily, there was at least at 24% higher odds of anxiety disorder diagnosis,” says study lead Karen Davison, health science faculty member, nutrition informatics lab director at Kwantlen Polytechnic University, (KPU) and North American Primary Care Research Group Fellow.
The study team analyzed data from the Canadian Longitudinal Study on Aging which included 26,991 men and women between the ages of 45 and 85. The article was published this week in the International Journal of Environmental Research and Public Health.
An important limitation of the study was that the assessment of anxiety disorders was based upon self-reporting of a medical diagnosis.
The authors also conducted multivariate analyses taking into account the use of a family physician in the past year to address the possibility of under-reporting of anxiety disorders among those who rarely visited health professionals. This adjustment was not found to substantially change the associations discussed above.
“It is estimated that 10% of the global population will suffer from anxiety disorders which are a leading cause of disability” says Karen Davison “Our findings suggest that comprehensive approaches that target health behaviors, including diet, as well as social factors, such as economic status, may help to minimize the burden of anxiety disorders among middle-aged and older adults, including immigrants.”
Depression is a major mental disorder worldwide. According to reports from the World Health Organization, the global prevalence of depression is 4.3%, with an incidence of 3.0%, and the condition is one of the leading causes of disability around the world [1, 2].
The prevalence of depression among Korean adults was estimated to be 5.6% in 2006 and 6.7% in 2011, and that increased to 10.3% in 2013 [3]. Depression is a mood disorder that includes feelings of worthlessness, being overwhelmed, and a lack of confidence.
It is related to reduced productivity and poor quality of life and can give rise to a higher risk of suicide [4]. The causes of depression have not been clearly identified, but they are known to be related to a variety of biological, genetic, psychological, and environmental factors [5].
In recent years, dietary nutrients have received attention for their potential to prevent and treat chronic diseases, including depression. Several healthy dietary patterns, such as the Mediterranean (high in vegetables, fruits, and olive oil) [6–8], traditional Japanese (rich in fruit, vegetables, green tea, and soy) [9], and traditional (rich in vegetables, fruit, fish, and unprocessed meat) [10, 11] diets, have all been reported to be negatively associated with depressive symptoms.
On the other hand, unhealthy dietary patterns, including processed foods such as sweets, fried food, processed meats, refined grains, and high-fat dairy [12], and a Western diet [9, 11, 13] have been reported to be positively associated with the odds of depression.
More evidence of an inverse association between fruit and vegetable consumption and depression in a Western population was reported by McMartin et al. [14], Mihrshahi et al. [15], Johnson et al. [16], and Ribeiro et al. [17]. Bishwajit et al. [18] reported that daily intake of fewer than five servings of fruits and vegetables was associated with higher odds of depression in a south Asian population. However, the prevalence of self-reported depression in Bangladesh, India, Nepal, and Sri Lanka averaged more than 35%, which seems to be an overestimation.
Studies of the association between vegetable and fruit intake and depression in the Korean population, whose average intake of fruits and vegetables is relatively high, are lacking, limited to an examination of the relationship between dietary patterns and depression in adolescent girls [19] and Korean adults [20].
Therefore, we used data from the 2014 Korea National Health and Nutrition Examination Survey (KNHANES) to investigate the association between vegetable and fruit intake and the prevalence of depression among Korean adults.
Discussion
In this study, we used 2014 KNHANES data to examine the correlation between vegetable and fruit intake and depression among Korean adults. We found that higher vegetable and fruit intake was significantly associated with a decreased prevalence of depression. Regarding the relevance of depression according to general characteristics, subjects who were female, aged 30–49 years, unemployed, or with a college or higher education exhibited a higher proportion of depressive symptoms than others.
Regarding dietary behavior and prevalence of depression, depression rates were higher among subjects who skipped lunch, were in the “mildly insecure” food security group, ate out 1–3 times/month, or consumed < 400 g of vegetables and fruits per day. Regarding nutrient intake, protein, fiber, calcium, phosphorus, iron, potassium, thiamine, and riboflavin levels were significantly lower in the depression group than in the non-depression group in the unadjusted data.
After adjustment for sex, age, and energy intake, only fiber and potassium were significantly lower in the depression group than in the non-depression group. Subjects in the depression group also consumed significantly less seaweed than those in the non-depressed group after adjustment.
Significantly, subjects with depression consumed less total food, legumes and their products, vegetables (non-salted and salted), fresh fruits, and other food than those without depression in both unadjusted and adjusted analyses. The odds of depression decreased significantly as the consumption of vegetables and fruits increased among all, male, and female subjects.
Miki et al. [31] investigated the association between dietary fiber and depressive symptoms among 1977 Japanese workers aged 19–69 years. They found that a greater intake of dietary fiber from vegetables and fruits correlated significantly with lower depressive symptoms. Major depression is primarily associated with imbalances in neurotransmitter production and transmission, such as serotonin receptor abnormalities, higher monoamine oxidase (to metabolize serotonin), and abnormalities in the expression of tryptophan hydroxylase (involved in serotonin synthesis) [32–34].
Recent studies have reported that the gut microbiota are important in the gut–brain axis and play a role in modulating brain function by altering the level of cytokines. Dietary fiber from vegetables, fruits, and other plants can help to improve the composition of intestinal microbiota [35].
Our results in this study also indicate that some micronutrients (calcium, iron, thiamin, and riboflavin) were significantly lower in the depression group than in the non-depression group (data not shown).
Some essential micronutrients, including calcium, zinc, iron, and folate, play important roles in depression through their regulation of cellular functions and neural transmission [36–40]. The inverse relationship between dietary iron and calcium intake and depression in this study is supported by several epidemiological and meta-analysis studies [40–42].
Calcium and iron are involved in the synthesis of neurotransmitters related to depression, such as serotonin and dopamine [43, 44]. The vitamin B complex, including thiamine and riboflavin, is essential for maintaining healthy immune and nervous systems.
Dietary vitamin B deficiency could thus be closely related to mental disorders such as depression, mood disorders, anxiety, and cognitive decline [45]. In a study of 1587 Chinese adults aged 50–70 years, Zhang et al. [46] reported that insufficient thiamine was significantly associated with higher odds of depression.
Another study reported that depressive patients who received thiamine supplementation showed improvement in depressive symptoms in as little as 6 weeks [47].
Our findings support previous studies that reported that healthy diets, including high vegetable and fruit intake, reduced the rates of depression and other mental health disorders. McMartin et al. [14] examined the association between fruit and vegetable intake and mental health disorders using a cross-sectional study of Canadians (n, 296,121 aged 12 years or older) five times between 2000 and 2009.
They found that fruit and vegetable intake was negatively associated with depression, psychological distress, and poor mental health. A meta-analysis of fruit and vegetable consumption and risk of depression (including 227,852 participants for fruit intake and 218,699 participants for vegetable intake) was reported by Lui et al. [48].
They also found that fruit and vegetable intake was inversely related to the risk of depression. The negative association between fruit intake and depression has thus been observed in both cross-sectional and cohort studies.
Johnson et al. [16, 17] reported an association between mental well-being and a community-based healthy living intervention that included greater fruit and vegetable consumption and physical activity.
They reported improvements in the mental well-being of participants 3 months after the healthy living intervention. Fruit and vegetable consumption greatly increased over time compared with physical activity, and greater fruit and vegetable consumption was associated with more positive changes in the mental well-being than physical activity. Mihrshahi et al. [15, 16] reported an association between fruit and vegetable intake prevalence and incidence of depressive symptoms in a study of 6271 middle-aged women from the Australian Longitudinal Study on Women’s Health.
They found that depressive symptoms were lower among subjects who ate more than two servings of fruits per day and that higher vegetable intake was negatively associated with the prevalence of depressive symptoms.
Kim et al. [49] reported an association between dietary patterns and depression among US adults using two waves (2007–2008 and 2009–2010) of National Health and Nutrition Examination Survey (NHANES) data. They found that the “healthy” dietary pattern (whole grains, vegetables, fruits, fish, nuts and seeds, and oil, with high consumption of protein, dietary fiber, polyunsaturated fat, vitamin C, vitamin A, β-carotene, vitamin E, vitamin D, calcium, and sodium) was negatively related to prevalence of depression in women. On the other hand, the Western dietary pattern did not show any relationship to depression among men or women.
Miki et al. [31] examined the relationship between dietary patterns and depressive symptoms in 2006 Japanese employees aged 19–69 years using an empirical dietary pattern method (reduced rank regression).
They found that a healthy dietary pattern that included high intakes of vegetables, fruits, mushrooms, seaweeds, soy products, green tea, potatoes, and small fish (including bones) and low rice consumption was negatively associated with depressive symptoms.
A cross-sectional study of 2266 Japanese employees aged 21–65 years showed that participants with high scores for the balanced Japanese dietary pattern (high intake of vegetables, including carrots and pumpkin, as well as typical Japanese foods such as mushrooms and seaweed) were significantly less likely than others to show depressive symptoms [4]. Jacka et al. [10, 11] reported that traditional Norwegian and Australian diets that included vegetables, fruit, meat, fish, and whole grains were also associated with a low incidence of depression. Similarly, a study by Sanchez-Villegas et al. [8] demonstrated that the Mediterranean diet might help to reduce depressive symptoms.
This study had some methodological limitations. First, the estimated food intake (including vegetable and fruit consumption) might not accurately reflect subjects’ usual food intake because the survey used the 24-h recall method. Second, the cross-sectional study design means that cause–effect relationships cannot be confirmed between vegetable and fruit intake and depression. For example, the low intake of vegetables and fruits among subjects with depression could be a result of appetite loss, which is a common depressive symptom. Third, our data assessed depression using a self-reported questionnaire (PHQ-9), not medical diagnoses by a specialist.
Despite these limitations, this study also has its strengths. First, it is a population-based study with a relatively high response rate and large sample size. Second, this is the first cross-sectional study to investigate associations between vegetable and fruit consumption and the prevalence of depression in an Asian population.
Most research on the association between vegetable and fruit intake and depression has been conducted in European countries. Studies that include Koreans, including our findings, remain very limited. Additional epidemiological and clinical randomized controlled trials are needed to clarify the role of vegetable and fruit intake in depression.
Source:
University of Toronto
