ABSTRACT

There is much epidemiological evidence suggesting a reduced risk of development of type 2 diabetes (T2D) in habitual coffee drinkers, however to date there have been few longer-term interventions, directly examining the effects of coffee intake on glucose and lipid metabolism. Previous studies may be confounded by inter-individual variation in caffeine metabolism. Specifically, the rs762551 SNP in the CYP1A2 gene has been demonstrated to influence caffeine metabolism, with carriers of the C allele considered to be of a ‘slow’ metaboliser phenotype. This study investigated the effects of regular coffee intake on markers of glucose and lipid metabolism in coffee-naïve individuals, with novel analysis by rs762551 genotype. Participants were randomised to either a coffee group (n 19) who consumed four cups/d instant coffee for 12 weeks or a control group (n 8) who remained coffee/caffeine free. Venous blood samples were taken pre- and post-intervention. Primary analysis revealed no significant differences between groups. Analysis of the coffee group by genotype revealed several differences. Before coffee intake, the AC genotype (‘slow’ caffeine metabolisers, n 9) displayed higher baseline glucose and NEFA than the AA genotype (‘fast’ caffeine metabolisers, n 10, P<0·05). Post-intervention, reduced postprandial glycaemia and reduced NEFA suppression were observed in the AC genotype, with the opposite result observed in the AA genotype (P<0·05). These observed differences between genotypes warrant further investigation and indicate there may be no one-size-fits-all recommendation with regard to coffee drinking and T2D risk.