For some, coffee is the true nectar of the gods, while others won't touch a drop of the stuff. Now, a new study reveals how genes influence people's preferences for a cup o' Joe.
Researchers analyzed genetic data from studies of more than 120,000 coffee drinkers of European and African-American ancestry. They found eight locations of the human genome linked with coffee drinking, six of which had never been linked to consumption of the beverage before, according to the study, published today (Oct. 7) in the journal Molecular Psychiatry.
The findings further boost the idea that a hit of caffeine is what motivates regular coffee consumption, and could explain why the same amount of coffee or caffeine can have enormously different effects on different people. [10 Surprising Facts About Coffee]
"Coffee, a major dietary source of caffeine, is among the most widely consumed beverages in the world and has received considerable attention regarding health risks and benefits," the researchers wrote in the study.
Research consistently suggests that drinking coffee is linked to a lower risk of type 2 diabetes, liver disease and Parkinson's disease, the researchers said. However, the effects of coffee on cancer risk, cardiovascular health, pregnancy and other conditions remain unclear.
In the study, researchers at the Harvard School of Public Health in Boston looked at the entire genomes of 90,000 coffee drinkers of European ancestry who had participated in 28 previous studies of regular coffee consumption.
They identified individual genetic differences, called single nucleotide polymorphisms (SNPs), which were associated with coffee consumption, and then conducted follow-up studies of about 30,000 and 8,000 coffee drinkers of European and African-American ancestry, respectively.
The researchers identified two new genes involved in how the body processes caffeine, POR and ABCG2. The found that those who drank more coffee were more likely to have certain variants of both of these genes, which encode proteins involved in caffeine metabolism.
They also found two regions of DNA near genes called BDNF and SLC6A4 that might play a role in how caffeine affects the brain by positive reinforcement. The study participants with a certain variant, who secrete less BDNF, may feel less of the rewarding effects of drinking coffee, according to the study. But the bigger coffee drinkers were more likely to have a certain variant of the SLC6A4 gene, which encodes a protein that transports the brain chemical serotonin.
They also identified regions near genes called GCKR and MLXIPL that are involved in sugar and fat processing, but had not been linked to the breakdown or neurological effects of coffee before. They found that people who drank more coffee were more likely to have a variant of the GCKR gene involved in glucose sensing in the brain, and that may affect how the brain responds to caffeine. The link between MLXIPL and coffee drinking remains unclear, the researchers said.
"Our results support the hypothesis that metabolic and neurological mechanisms of caffeine contribute to coffee consumption habits," the researchers wrote.
In addition, the findings help explain the difference in coffee consumption among people.
So, next time you reach for that sixth cup of coffee, just blame it on your genes.