Association of heavy metals and bio-elements blood level with metabolic syndrome: a systematic review and meta-analysis of observational studies.

Background and objectives: The literature has reported heavy metals might alter the physiological and biochemical functions of body organs and cause several health problems. So, the present systematic review and meta-analysis aimed to investigate the association of blood levels of essential or non-essential metals with metabolic syndrome (MetS). Methods: In this systematic review, some international databases including PubMed, Embase, Scopus, and Web of Science were searched up to February 2024. All observational studies which assessed the association of three heavy metals (cadmium, mercury, lead) and bio-elements (chromium, iron, manganese, and magnesium, copper) with the risk of MetS were included. There was no limitation in the time of publication and language. A random-effects meta-analysis was performed to estimate the pooled effect sizes. Possible sources of heterogeneity were explored by meta-regression analysis. Results: Totally, 29 studies were eligible for meta-analysis. Our results showed that increased level of cadmium (pooled OR: 1.24, 95% CI: 1.05, 1.46) and mercury (pooled OR: 1.22, 95% CI: 1.08, 1.38) significantly increased the risk of MetS. In contrast, increased level of chromium significantly reduced the risk of developing MetS (pooled OR: 0.68, 95% CI: 0.56, 0.83). Moreover, association between lead, iron, copper, magnesium, and manganese with MetS was not statistically significant (P > 0.05). However, elevated lead levels in men increased the odds of MetS. Conclusion: Our results show a significant association between blood levels of some heavy metals, including cadmium, mercury, and lead, with increased odds of MetS. On the other hand, chromium as a biometal decreased the odds of MetS. Supplementary Information: The online version contains supplementary material available at 10.1007/s40200-024-01500-9.