Journal of Clinical Nutrition & Dietetics

Abstract

Caffeine is the most widely consumed physiological stimulant worldwide. Its effects on metabolic syndrome outcomes have been controversial at a population level. This review systematically investigates evidence from both, Randomized Controlled Trials (RCTs) and non- RCTs, how do some caffeine metabolism-related polymorphisms influence the effect of caffeine consumption on metabolic syndrome outcomes. Two databases (PubMed and EMBASE) were independently searched using almost the same algorithm. Included studies that involved only human participants and explored the influence of any genetic polymorphisms related to caffeine and metabolic syndrome outcomes. We included 16 studies (four randomized controlled trials, one interventional and quasi-interventional, seven crosssectional studies, and four case-control studies). Cytochrome P450 (CYP1A2) single nucleotide polymorphisms and the family of adenosine receptor (ADORA) genotypes, mostly ADORA2A, were associated with caffeine consumption and metabolic outcomes. However, the findings are controversial, and betterdesigned studies with larger sample sizes, fewer confounders, and better estimation of caffeine intake are needed in the Future.