Associations of coffee genetic risk scores with consumption of coffee, tea and other beverages in the UK Biobank

AIMS To evaluate the utility of coffee-related genetic variants as proxies for coffee consumption in Mendelian randomization studies, by examining their association with non-alcoholic beverage consumption (including subtypes of coffee and tea) and a range of socio-demographic and life-style factors. DESIGN Observational study of the association of genetic risk scores for coffee consumption with different types of non-alcoholic beverage consumption. SETTING UK general population. PARTICIPANTS Individuals of European ancestry aged 40-73 years from the UK Biobank between 2006 and 2010 (n = 114 316). MEASUREMENTS Genetic risk scores were constructed using two, four and eight independent single nucleotide polymorphisms (SNPs) identified in genome-wide association studies (GWAS) of coffee consumption. Drinks were self-reported in a baseline questionnaire (all participants) and in detailed 24 dietary recall questionnaires in a subset (n = 48 692). FINDINGS Genetic risk scores explained up to 0.38, 0.19 and 0.76% of the variance in coffee, tea and combined coffee and tea consumption, respectively. Genetic risk scores demonstrated positive associations with both caffeinated and decaffeinated coffee and tea consumption, and with most subtypes of coffee consumption, but only with standard tea consumption. There was no clear evidence for positive associations with most other non-alcoholic beverages, but higher genetic risk for coffee consumption was associated with lower daily water consumption. The genetic risk scores were associated with increased alcohol consumption, but not consistently with other socio-demographic and life-style factors. CONCLUSIONS Coffee-related genetic risk scores could be used as instruments for combined coffee and tea consumption in Mendelian randomization studies. However, associations observed with alcohol consumption require further investigation to determine whether these are due to causal effects of coffee and tea consumption or biological pleiotropy.