Objective: Vegetarian diets contain various anti-inflammatory components. We aimed to investigate the effects of vegetarianism on inflammatory biomarkers when compared with omnivores.Design: Systematic review and meta-analysis.Setting: Literature search was conducted in Science Direct, Proquest, MEDLINE and Google Scholar up to June 2016. Summary estimates and corresponding 95 % CI were derived via the DerSimonian and Laird method using random effects, subgroup analyses were run to find the source of heterogeneity and a fixed-effect model examined between-subgroup heterogeneity.Subjects: Studies were included if they evaluated effects of any type of vegetarianism compared with omnivores on circulating levels of inflammatory biomarkers. No restriction was made in terms of language or the date of study publications.Results: Eighteen articles were included. Pooled effect size showed no difference in high-sensitivity C-reactive protein (hs-CRP) levels in vegetarians v. omnivores (Hedges’ g=−0·15; 95 % CI −0·35, 0·05), with high heterogeneity (I²=75·6 %, P<0·01). A subgroup analysis by minimum duration of vegetarianism showed that a minimum duration of 2 years vegetarianism was associated with lower hs-CRP levels v. omnivores (Hedges’ g=−0·29; 95 % CI −0·59, 0·01), with moderate heterogeneity (I²=68·9 %, P<0·01). No significant effect was found in studies using a minimum duration of 6 months of vegetarianism, with low heterogeneity. Vegetarianism was associated with increased IL-6 concentrations (0·21 pg/ml; 95 % CI 0·18, 0·25), with no heterogeneity (I²=0·0 %, P=0·60).Conclusions: The meta-analysis provides evidence that vegetarianism is associated with lower serum concentrations of hs-CRP when individuals follow a vegetarian diet for at least 2 years. Further research is necessary to draw appropriate conclusions regarding potential associations between vegetarianism and IL-6 levels. A vegetarian diet might be a useful approach to manage inflammaging in the long term.

The results of human studies are inconsistent regarding selenium and depressive disorders. Therefore, we aimed to conduct a systematic review and meta-analysis of observational and interventional studies and provided an overview of the role of selenium in depression. Three databases including Medline, Scopus, and Web of Science were searched on June 30, 2020 and updated on April 12, 2021. Also, we searched in electronical databases of WHO Global Index Medicus and ClinicalTrials.gov. No time or language restrictions were used for the search. A random effects model was used to pool effect sizes. In total, 20 studies were included in the systematic review, and 15 studies were included in the meta-analysis. There were no significant differences in serum selenium levels between patients with depression and healthy subjects (WMD: 2.12 mg/L; 95% CI: − 0.11, 4.36; I² = 98.0%, P < 0.001). Also, no significant correlation was found between serum levels of selenium and depression scores (r: − 0.12; 95% CI: − 0.33, 0.08; I² = 73.5%, P = 0.010). Nevertheless, there was a significant negative association between high selenium intake and the risk of postpartum depression (OR: 0.97; 95% CI: 0.95, 0.99; I² = 0.0%, P = 0.507). In addition, selenium supplementation significantly reduced depressive symptoms (WMD: − 0.37; 95% CI: − 0.56, − 0.18; I² = 0.0%, P = 0.959). Taken these results together, selenium seems to have a protective role against postpartum depression and can be considered as a beneficial adjuvant therapy in patients with depression. Further studies are necessary to draw definitive conclusions.

Background: Hyperhomocysteinaemia is known to interfere with neurological functions; however, there is a controversy regarding the relationship between homocysteine and depression. Materials and methods: Science Direct, MEDLINE and ISI Web of Science were searched to find relevant articles, published up to August 2020. Studies were included if they compared homocysteine levels in healthy subjects with subjects with depression. Also, articles that reported the association between hyperhomocysteinaemia and risk of depression were included. Odds ratios of depression and means of homocysteine were used to ascertain the overall effect size. Results: Homocysteine level was higher in subjects with depression in comparison with healthy controls (weight mean difference = 2.53 µmol/L, 95% confidence interval: 1.77, 3.30), and the depression diagnostic tool was a source of heterogeneity. Homocysteine level was significantly higher in subjects with depression in studies that used Diagnostic and Statistical Manual of Mental Disorders‐IV (DSM‐IV), Geriatric Depression Scale (GDS), Zung Self‐Rating Depression Scale (ZDRS) and Beck Depression Index II (BDI‐II) as depression diagnostic tools. Also, participants with hyperhomocysteinaemia had a higher chance of depression (Pooled risk = 1.34, 95% confidence interval: 1.19, 1.52), where the depression diagnostic tool was a source of heterogeneity. In contrast to ZDRS and Patient Health Questionnaire (PHQ) subgroups, hyperhomocysteinaemia yielded a significantly higher risk of depression in DSM‐IV, GDS and ‘other’ subgroups. Conclusion: Homocysteinemia level is higher in individuals with depression. However, the depression diagnostic tool used is instrumental in influencing their association, and thus, future studies should focus on the tools for depression assessment.