In the current study evaluating the relation between DPI and psychologic disorders, we observed that higher intake of phytochemical-rich foods was inversely associated with risk of depression and anxiety symptoms in participant with normal BMI. These protective relations remained significant after adjusting for a wide range of possible confounding variables. To the best of our knowledge, this study is among the first study exploring the DPI-psychological disorders relationship in a large population from a Middle-Eastern country where the prevalence of psychological disorders is higher than other part of the world (22).
A long-standing studies have been showed that food or dietary pattern with fluent phytochemical are protective for mental health, for instances, results of cohort study shown that high intake of flavonols, flavones and flavanones were inversely associated with risk of depression (23). Another study reported that high intake of phenolic acid, flavanones and anthocyanins significantly decrease risk of depressive (24). Some studies reported that "prudent", “lacto-vegetarian” and " healthy " dietary pattern characterized by high intakes of phytochemical rich foods including fruits, vegetables, medium fat dairy, nuts, legumes and fish was protectively associated with depression and anxiety (22, 25). In addition, some other studies confirmed the health benefit effects of DPI on abdominal obesity, lipid profile and insulin resistant (13, 14). In contrast with our results, a cohort study reported high intakes of flavan-3-ols and anthocyanins were not significantly associated with depression risk in women (23). Other study explained that higher consumption of high phytochemical foods such as fruits and vegetables was not associated with levels of depressive symptoms among males (26) Also, there was not any significant association between DPI and inflammatory markers as a mediator of psychological disorders in another research (27).
Inflammatory markers such as serum levels of C-reactive protein, tumor necrosis factor alpha and Interleukin 6 were related with mental health in previous studies (28, 29). So, the pro-inflammatory cytokines create numerous clinical distinct of depression such as disrupted serotonin metabolism, overactivity of the hypothalamus–pituitary–adrenal axis and
neurovegetative symptoms (30). Phytochemical disrupt production of pro-inflammatory mediators such as these derived from the arachidonic acid cascade. This derived components can be inflammatory effect via modulating neuro-inflammation by cooperation with p38 signaling cascades and STAT-1 (31). Fruits and vegetable are main sources of folate. Results of some studies shown that there are association between serum folate and dietary intake of this vitamin and depression (25, 32, 33). It can be effect on mental health via methylation in the nervous system (32). Numerous psychiatric disorders were associated to oxidative stress. Brain is attainted especially susceptible to oxidative damage. Brain relatively consumes high oxygen and consequently higher production of free radical also brain has lipid-rich structure that vulnerable for oxidation (34, 35). Phytochemical are powerful antioxidants. It by donating an electron or hydrogen atom can able to neutralize free radicals (8).
Our results showed no significant association between stress and DPI. Few studies investigated association between food group and symptom stress. Results of cohort study shown that Mediterranean Diet Score was inverse association with psychological distress. This score was computed on the basis frequencies of intake vegetables, fruit, cereals, legumes and fish (36). The results of our studies were inconsistent with previous studies. The reason for inconsistency probably was using different questionnaires to diagnose psychological distress. Also one study conducted only on 488 women while sample sizes of our study are higher and conducted both men and women.
There was no any significant association between DPI and psychological disorders in overweight and obese subjects. Few studies investigated association between food groups and psychological disorders in overweight and obese subjects. In consistent with our, other study reported that there was no association between traditional and lactovegetarian dietary pattern with high DPI-food such as vegetables, fruit and wholegrain
and psychological disorders in obese participant (22). Probably obesity can cause mental disorders in other ways, which has mitigated the phytochemical effects on mental disorders. Obese and overweight usually have negative body image. There is evidence that shown relationship between depressive symptoms and anxiety with body image dissatisfaction (37). Some studies revealed that obesity acts a role in development of psychopathological disorders such as anxiety and psychosis via begin low self-esteem (38, 39).
This study has several strengths. We adjusted for a wide range of potential confounders that might affect psychological conditions, also the large represented sample size of the study including both sexes. Stratified results base on BMI as an important dietary variable related with psychological disorders was presented. This study has some limitations. First the cross-sectional study was not show causal relationship between mental health and DPI. Second we undertake to control for manifest confounding factors however may has been some residual confounding. Third DPI does not include non-caloric phytochemical-rich food such as green and black tea that are sources of phytochemicals. finally, DASS questionnaire do not provide diagnostic of disorders and only estimate symptoms of depression and anxiety.