Original articleDietary inflammatory index (DII®) and the risk of depression symptoms in adults
Introduction
The World Health Organization (WHO) estimates that 322 million people live with depression globally [1]. In Australia, one in ten people (10.4%) had depression or feelings of depression in 2017–18 [2], representing a significant public health problem. Depression is a multifactorial disease with biological, psychological, social and behavioural determinants [3]. Of these factors, diet [4] and inflammation [5,6] have been found to be important predictors of depression.
Increased levels of inflammatory markers, such as C-reactive protein (CRP), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α), have been linked with depression [7,8]. In a meta-analytic study of CRP levels, to determine the prevalence of low-grade inflammation among both sexes, nearly 1 in 4 patients with depression showed evidence of low-grade inflammation (CRP>3 mg/L), and 58% exhibited mildly elevated CRP (>1 mg/L) [9]. In addition to inflammatory biomarkers, food and nutrients have pro-/anti-inflammatory properties that may have an effect on depression [10].
Some studies have shown that the inflammatory capacity of diet was associated with an increased risk of depression symptoms (DepS) [[10], [11], [12]]. However, evidence from both cross-sectional [[13], [14], [15], [16], [17], [18], [19], [20], [21]] and longitudinal studies [[22], [23], [24], [25], [26], [27], [28], [29]] has shown an inconsistent association between the inflammatory potential of diet and depression/DepS. In addition, many of these studies have limited generalizability as they used specific cohorts, such as middle-aged women [28], older adults (>65 years) [29], female nurses [25], university graduates [26], primary care centres participants [17], health care centres participants [18] and office-based civil servants [24], rather than the general population. Further, these studies have not investigated the link between the Energy-adjusted Dietary Inflammatory Index (E-DII™) and specific components of the depression score such as depressed mood, feelings of guilt and worthlessness, feelings of helplessness and hopelessness, psychomotor retardation, loss of appetite, and sleep disturbance.
Therefore, this study aimed to explore the association between E-DII score and DepS in a representative sample of Australian adults, focussing on identifying specific DepS (from CES-D items) and updating the previous, most recent meta-analysis [30] by including the new data from the North West Adelaide Health Study (NWAHS) cohort.
Section snippets
Data source and subjects
The data for this study were collected as part of the NWAHS, which is a longitudinal cohort study that recruited participants from the northern and western suburbs of Adelaide, South Australia. Three clinic-based stages of data collection were have been conducted: 1999–2003, 2004–2006, and 2008–2010 [31]. In addition, a self-completed survey (postal or online) was conducted in 2015 (NW15). In the three clinic-based stages, in addition to the clinical assessments, data were collected using
Meta-analysis on DII and DepS
We updated a previous meta-analysis [30], which involved a search of the literature up to 3rd October 2018, to include the NWAHS findings. The meta-analysis techniques were undertaken using similar methods as those used previously by Tolkien et al. [30]. We then conducted literature searches in PubMed® and Scopus® from 4th October 2018 to 15th May 2020 based on the following search terms: ‘inflammat∗’ AND ‘diet’ AND ‘depress∗’. Relevant articles were obtained and included in the meta-analysis
Descriptive characteristics
The mean age (SD) of participants at Stage 3 was 56.6 (SD 13.6) years, ranging from 24 to 94 years. The mean E-DII in this study was −1.30 (SD 1.35), and the scores ranged from −4.53 (most anti-inflammatory) to +3.79 (most pro-inflammatory). The anthropometric, socioeconomic and clinical characteristics of the participants stratified by quartiles of E-DII are illustrated in Table 1. As compared to subjects in the most anti-inflammatory E-DII category (Quartile 1), those in the most
Discussion
This study explored the association between the E-DII and DepS using multiple approaches. First, we used a large community-based cohort to determine the cross-sectional and longitudinal association between E-DII and DepS. Second, we explored the association between E-DII scores and DepS by focussing on individual CES-D items to explore associations with specific DepS. Third, we updated the available data using meta-analytic techniques. To the best of our knowledge, no previous study has
Conclusions
In conclusion, data from this study support a positive association between a pro-inflammatory diet and increased risk of DepS. Our findings support the current recommendation of increasing the consumption of an anti-inflammatory diet and decreasing consumption of a pro-inflammatory diet to improve DepS. However, current evidence on the role of diet-induced inflammation in DepS should be reinforced using further longitudinal studies with extended follow up, larger sample sizes and repeated
Author contributions
All authors conceived the study; PRS drafted the manuscript; PRS and YAM analyzed the data; NS and JRH designed the dietary inflammatory index; YAM, AJP and TKG commented on each draft of the paper. AJP, RJA and TKG provided critical revisions of the manuscript for relevant intellectual content. All authors have read and approved the final version of the manuscript for publication. TKG has primary responsibility for final content.
Conflict of interest
All authors declare no conflict of interest. Wish to disclose that Dr. James R. Hébert owns controlling interest in Connecting Health Innovations LLC (CHI), a company that has licensed the right to his invention of the dietary inflammatory index™ (DII®) from the University of South Carolina in order to develop computer and smart phone applications for patient counseling and dietary intervention in clinical settings. Dr. Nitin Shivappa is an employee of CHI. The subject matter of this paper will
Acknowledgments
We thank all of the participants from North West Adelaide Health Study (NWAHS) and all the members of the team comprising of research scientists, statisticians, study coordinators, nurses, data managers, administrative assistants, and data entry staff, all of whom make the study possible. PRS was supported by Adelaide Scholarship International (ASI) scholarship provided by the University of Adelaide. The authors are also grateful to all of the providers of research funds for this project
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2022, Clinical NutritionCitation Excerpt :Accordingly, nutrition has received more attention in the last decade as a modifiable lifestyle risk factor for depression [10], with a particular focus on the consumption of specific foods that might modulate inflammatory factors [11,12]. Several prospective cohort studies have investigated the associations between the potential inflammatory effects of diet and the incidence of self-reported diagnosis of depression [13,14] or depressive symptoms [15–19] throughout adulthood. However, only a few of these studies have examined this association specifically in older people [19] or stratified by older adult age subgroup [16,17].
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2022, Journal of Affective DisordersCitation Excerpt :The possible explanation for the positive association between DII and depression is that the cumulative diet inflammatory potential may affect the brain immune, antioxidant defense and neurotrophic systems. A pro-inflammatory diet has been shown to increase chronic and sustained activation of the immune system, leading to mild inflammation(Shakya et al., 2021). Evidence suggests that some cytokines may cross the blood-brain barrier, transmitting signals to the brain through afferent nerves that influence brain functions(Miller and Raison, 2016) and promote depressive-like behaviors(Chourbaji et al., 2006; Dantzer et al., 2008; Simen et al., 2006).