Diet and Inflammation

Association of the Dietary Inflammatory Index with depressive symptoms among pre- and post-menopausal women: Findings from the National Health and Nutrition Examination Survey (NHANES) 2005–2010

Depression, affecting more than 350 million people across the world, has been recently associated with a state of low-grade chronic inflammation. Our diets were found to play a role in the development of a pro-inflammatory state, where the consumption of foods that scored high on the Empirical Dietary Inflammatory Index (EDII) was associated with an increase in circulating plasma inflammatory markers. The EDII is a validated new tool that focuses on the weekly consumption of sixteen net pro- or anti-inflammatory food groups, a tool that has not been used yet in the rising number of studies linking pro-inflammatory diets to depression. The relationship between diet and depression is yet to be fully understood, meanwhile, the use of pharmacologic therapies continues to be considered our most advanced treatments for major depressive disorders, despite several studies suggesting that such methods are insufficient. Identifying the need to explore the relationship between pro-inflammatory diets and depressive symptoms to achieve a holistic, evidence-based treatment approach, Belliveau, R., Horton, S., Hereford, C. et al (2022) endeavored to investigate this relationship using the EDII, coupled with a Patient Health Questionnaire-9 (PHQ-9) to score depression amongst a population of healthcare personnel. The results obtained from 631 participants demonstrated a significant association between pro-inflammatory diets and depression while accounting for variables such as gender, psychiatric diagnosis, and physical and spiritual exercise. The findings demonstrated that participants who reported eating fewer leafy greens, consuming greater amounts of bread or pasta, sugar- sweetened beverages, and processed meats (a diet that ranks high on EDII) scored higher on PHQ-9 and suffered more depressive symptoms when compared to their peers. The authors conclude that anti-inflammatory diets can play a key role in the treatment of depression. [NPID: Depression, nutrition, empirical dietary inflammatory index, EDII, DI, patient health questionnaire (PHQ-9), healthcare]

The purpose of this 2021 review was to sum up the relationship between inflammation and depression. While there is substantial evidence linking inflammation with the development of depression, the diverse nature of depression has limited the understanding, prevention, and treatment of this disease. The article looks at the core features of depression such as overreacting to negative information, changes in reward processing, declining cognitive control, and somatic syndrome. The reviewers analyzed how each core feature relates to depression and investigates the potential role of inflammation. The authors concluded that inflammation may play a factor in several characteristics of depression, including overreaction to negative information, altered reward responses, and physical symptoms. There was less evidence supporting the influence of inflammation on cognitive control. The review then discusses what these results may mean for research in the future. [NPID: review, inflammation, depression, depressive symptoms, dietary inflammatory index]

Since inflammation is known to induce mitochondrial dysfunction in the nervous system, this 2017 study tested whether mitochondrial dysfunction contributes to lipopolysaccharide (LPS)-induced depression-like behavior in mice. Another goal of this study was to check if the antioxidant resveratrol alleviates inflammation-induced depressive-like behavior by preventing mitochondrial dysfunction in the hippocampus. It was found that the liposaccharide (LPS) caused mitochondrial oxidative stress and dysfunction in the mice, but these effects were attenuated by injection of the antioxidant Mito-TEMPO (targets the mitochondria). The mice treated with LPS exhibited depressive-like behaviors in the forced swimming test. It was reported that both Mito-TEMPO and resveratrol could significantly improve these depressive-like behaviors. In contrast, injecting rotenone (an inhibitor of the mitochondrial respiratory chain) induced mitochondrial oxidative stress and dysfunction in the hippocampus, resulting in depressive-like behaviors. In conclusion, resveratrol can have an antidepressant-like impact in mice showing LPS-induced depression-like behavior. This data supports the potential use of resveratrol as a future therapy agent for depression. [NPID: depression, inflammation, mitochondrial dysfunction, resveratrol, antidepressant]

Phillips et al. (2019) point out that there have been 480,000 references to inflammation by articles on diet and health in the National Library of Medicine database, in addition to 30,000+ peer-reviewed articles published on the relationship between diet, inflammation, and health outcomes. With this vast amount of evidence, it is now established that chronic systemic inflammation is associated with most non-communicable diseases (NCDs), including diabetes, obesity, cardiovascular disease, cancers, respiratory and musculoskeletal disorders. Since dietary constituents can influence the level of inflammation in a person, a dietary inflammatory index (DII) has been recently created to calculate the inflammatory potential of diet. While evidence linking this dietary inflammatory index with the risk of various NCDs has grown, this review aims to inspect the current state of research regarding DII’s relationship with cancers, neurodevelopment, mental health outcomes, as well as cardiometabolic, respiratory and musculoskeletal diseases. This article collected the findings of recent studies, discussed possible underlying mechanisms, and commented on future avenues of investigation in this field of nutritional research. [NPIDs: insomnia, sleep, sleep disorders, inflammation, non-communicable disease, diabetes, obesity, cardiovascular disease, cancer, respiratory disorders, musculoskeletal disorders, inflammatory index, cancer, neurodevelopment, cardiometabolic diseases, respiration, musculoskeletal]

The aim of this 2017 study was to examine the relationship between the inflammatory potential of the diet and the presence of incident depressive symptoms, while also investigating the modulatory roles of sex, age, physical activity, and smoking status. Adjibade et al. recruited the 3523 participants of the SU.VI.MAX (Supplémentation en Vitamines et Minéraux Antioxydants) cohort, who were all initially free of depressive symptoms. Over an average follow-up period of 12.6 years, there were 172 reports of incident depressive symptoms. The dietary inflammatory index (DII), which measures the inflammatory potential of the diet, was not related to incident depressive symptoms among the sample population. However, DII was positively linked with risk of incident depressive symptoms in men. When the subjects were sorted by smoking status, current and former smokers with higher DII scores were also found to be more likely to show incident depressive symptoms. Finally, another meaningful relationship was identified between less physically active individuals and increased odds of depressive symptoms. To conclude, this study suggests that eating a healthy diet with anti-inflammatory properties might prevent signs of depression, especially among men, smokers, and physically inactive people. [NPIDs: insomnia, sleep, sleep disorders, inflammation, depression, smokers, physical activity]

While the previous study conducted by Noronha et al. reported the obesity-inducing potential of high-fat diets in rats (with elevated anxiety-related defensive behaviors and reactivity to stress), this present study published in 2019 induced obesity in rats and assessed their anxiety-related defensive behavioral responses. Also, their thermoregulatory responses to stress were tested through an open field assessment. Nine weeks of the fat-enriched diet induced obesity in the rats and increased their anxiety-related defensive behavioral responses and proinflammatory cytokine levels in several regions of their brain. Moreover, the rats’ tail skin temperature rose from the beginning and throughout the open field test. These results support the hypothesis that the high-fat diet induces neuroinflammation, heightens reactivity to stress, enhances anxiety-like defensive behavioral responses, and modifies excitability of brain nuclei that regulate neuroendocrine, autonomic, and behavioral responses to stressful stimuli. [NPIDs: insomnia, sleep, sleep disorders, obesity, stress, reactivity, anxiety, fat, neuroinflammation, behavior, neuroendocrine response]

Ashton et al. (2020) examined a randomized controlled trial on the impact of several nutraceutical treatments on patients with bipolar depression. The 133 participants received 16 weeks adjunctive treatment of either placebo or N-acetylcysteine (alone or combined with mitochondrial-enhancing nutraceuticals). Four weeks after stopping the treatment, the subjects were assessed on diet (quality, inflammatory potential), body mass index, and other significant outcomes (depression symptoms, clinician-rated improvement, and functioning measures). Neither the Australian Recommended Food Score (measure of diet quality), dietary inflammatory index, nor body mass index scores could predict change in depression scores when comparing the combination treatment group with the placebo group. However, participants with better diet quality showed reduced general depression, bipolar disorder symptoms, and greater clinician-rated improvements, regardless of treatment and time. Moreover, a more anti-inflammatory diet (lower dietary inflammatory index score) was linked with less impairment in functioning. It was also suggested that the combination treatment of nutraceuticals may reduce the adverse effects of the pro-inflammatory diet on functioning. Furthermore, cohorts with lower BMIs who were given the combination therapy or N-acetylcysteine alone were reported to show better improvements by the clinicians. Although these results should be interpreted cautiously because of limitations, the data implies that there is an association between quality and inflammatory potential of diet, BMI, and the response to nutraceutical treatment for bipolar disorder in this clinical trial. [NPIDs: insomnia, sleep, sleep disorders, inflammation, depression, Australia, diet quality, bipolar, nutraceuticals, N-acetylcysteine]

In this 2019 study, a mental health disorders profile score was calculated for each Iranian adult participant using regression analysis and based on their levels of anxiety, depression and psychological distress. Haghighatdoost et al. aimed to evaluate the relationship between the subjects’ dietary inflammatory index (DII) and the risk of a worsened mental health disorders profile. The DII scores were calculated based on consumption of 27 macro- and micro-nutrients, onions, teas, and caffeine, which were all obtained through the food frequency questionnaires. The results from the analysis models indicated that participants with the lowest dietary inflammatory index scores (lowest quartile) were less likely to be in the top tertile for mental health disorders profile. Similar relationships were found among both genders, but associations appeared to be more significant in men. The data suggests that the pro-inflammatory characteristics of the diet are directly associated with an increased risk of worse mental health disorder profiles. [NPIDs: insomnia, sleep, sleep disorders, Iran, anxiety, depression, psychological distress, inflammatory index, macros, macronutrients, micronutrients, onions, teas, caffeine]

This 2021 study assessed a sample of Iranian adults on their food consumption to determine their food-based dietary inflammatory index (FDII). The aim was to investigate the relationship between the participants’ FDII and their risk of psychological disorders. The Iranian validated version of Hospital Anxiety and Depression Scale (HADS) and General Health Questionnaire (GHQ) were both used to examine psychological disorders. Results showed that people with the highest FDII scores (top quartile) had greater risks of depression, anxiety, and psychological distress, compared with those with the lowest FDII scores (lowest quartile). When this association between FDII scores and several mental health outcomes was further analyzed according to the subjects’ gender, food-based dietary inflammatory index scores were found to significantly correlate with increased incidences of depression, anxiety, and psychological distress among women. However, no significant link was identified when the highest and lowest quartiles for FDII scores were compared with one another in men. Nevertheless, Salari-Moghaddam et al. conclude that higher food-based dietary inflammatory index scores were related to greater prevalence of psychological disorders. [NPIDs: insomnia, sleep, sleep disorders, Iran, depression, anxiety, psychological distress, inflammation, inflammatory disorder]

While there is evidence suggesting a positive correlation between immune-inflammatory signalling and mood symptoms, McNamara (2015) focuses his attention on long-chain omega-3 (LCn-3) fatty acids such as eicosapentaenic acid (EPA) and docosahexaenoic acid (DHA), which have anti-inflammatory properties. Mental disorders such as mood, bipolar, and major depressive disorder, are thought to be associated with low EPA and/or DHA biostatus, greater LCn-6: LCn-3 fatty acid ratio, and higher levels of various proinflammatory proteins. It is proposed that medications that reduce depressive symptoms or stabilize mood in manic depression disorder may be effective partly due to the reduction of immune-inflammatory signaling and augmented by anti-inflammatory medication. Furthermore, recent studies have implied that a higher LCn-6: LCn-3 fatty acid ratio may elevate risk of developing depression and feeling irritable. The author thus believes that increasing consumption of LCn-3 fatty acids may be a simple strategy to lessen the negative impact of increased immune-inflammatory signaling on mood stability. [NPIDs: insomnia, mood, omega-3s, EPA, DHA, inflammation, anti inflammatory, irritation, depression, sleep, sleep disorders]