you can blame your parents for giving you the coffee-loving gene. Harvard researchers say the difference between someone who sips a single cup of coffee in the morning, and someone who guzzles 4 cups, is genetic. The Harvard team says there’s a cluster of genes that regulate how we react to caffeine. It’s why some people feel buzzed and happy – and others feel sick to their stomach. In fact, the genes that influence our coffee consumption are as strong as the ones that influence how we react to alcohol and cigarettes.