From a coffee drinker's point of view, there are only two kinds of people in the world: those who need their morning jolt and those who don't. As it turns out, there's a genetic component for this need for caffeine. A team of researchers have stirred through a comprehensive search of the human genome involving more than 47,000 participants, and found two genes that appear to be responsible for the amount of caffeine an individual drinks.
The genes are CYP1A2, which researchers had previously known was involved in the metabolism of caffeine, and AHR, which is involved in regulation of CYP1A2. People with the highest-consumption genotype for either gene consumed around 40 mg more caffeine than those with the lowest-consumption genotype--those who consume around 1/3 cup of caffeinated coffee, or a can of cola.
"We know caffeine had an inherited component, but for the first time we know specifically the major genes involved," Dr. Neil Caporaso, a senior investigator in the study, told ABC News. "Genetic studies have identified many associations with diseases, but very few for diet agents."
Knowledge of the genetic determinants of caffeine intake may provide insight into underlying mechanisms and provide ways to study the potential health effects of caffeine more comprehensively, the authors wrote in the open-access journal PLoS Genetics.