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 single nucleotide polymorphism (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 4 cups/day instant coffee for 12 weeks or a control group (n=8) who remained coffee/caffeine free. Venous blood samples were taken pre- and post13 intervention. Primary analysis revealed no significant differences between groups. Analysis of the coffee group by genotype revealed several differences. Prior to coffee intake, the AC genotype (“slow” caffeine metabolisers, n=9) displayed higher baseline glucose and non esterified fatty acids (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.