Coffee and metabolic impairment: An updated review of epidemiological studies

Background: Coffee is one of the most consumed beverages worldwide. In the last years, coffee consumption has been associated with a number of beneficial effects against metabolic impairment. The aim of this narrative review was to report the most updated and comprehensive evidence from epidemiological and experimental studies as well as mechanisms of action of coffee on metabolic impairment. Methods: A search in electronic databases (PUBMED and EMBASE) was performed to retrieve systematic and pooled analyses on coffee and diabetes, hypertension, and dyslipidemia. Furthermore, the most accredited hypotheses and mechanisms of action of coffee have been described. Results: Coffee consumption has been associated with reduced risk of diabetes in observational studies. However, the effect seems not to be mediated by caffeine. Contrasting results have been found in pooled analyses of observational studies on hypertension, despite short- and long-term follow-ups that have been demonstrated to influence the outcome. Poor or little effect on plasma lipids has been reported in studies on acute administration of coffee, yet depending on the type of coffee preparation. The main beneficial effects of coffee consumption seem to rely on the content of antioxidant and anti-inflammatory compounds (i.e., polyphenols). Among the most important, chlorogenic acids have demonstrated direct anti-hypertensive action through beneficial effect on endothelial function, and significant improvement in glucose and insulin metabolism. Also, diterpenes and melanoidins are major candidates as antioxidant compounds showing the capacity to inhibit the production of inflammatory mediators. However, caffeine and diterpenes may also exert negative effects, such as acute rise in blood pressure and serum lipids. Conclusion: In light of the most recent evidence, coffee consumption seems to be favorably related with health and to protect by metabolic impairment.