A new study has indicated that genes determine how much caffeine a person consumes in the form of coffee, tea, soda, and chocolates. Two genetic variations that influence the metabolism of caffeine are also associated with how much of caffeine a person consumes. Study leader Marilyn C. Cornelis, PhD, of the Harvard School of Public Health, reports that people with a particular variation in these genes tend to have more caffeine. The two genes identified to be associated with more consumption of caffeine are CYP1A2 and AHR. CYP1A2 is already known to play an important role in metabolism of caffeine while AHR affects the regulation of CYP1A2. All people carry these two genes involved in the metabolism of caffeine.
In this study on 47,000 Americans of European descent, people who had the high-consumption variant of the gene consumes approximately 40 mg more caffeine when compared to people who have the low-consumption variant of the gene. This is equivalent to 1/3 cup of caffeinated coffee or a can of soda. Researchers say that many people drink more not to achieve the pleasurable limits but to avoid withdrawal symptoms. This may suggest that these people might have the genetic variation for a fast metabolism of caffeine. They also add that genetics may play a major role in behaviors like alcohol consumption and smoking also.
For this study, the researchers analyzed the average coffee consumption through coffee, tea, caffeinated sodas or chocolate, in people participating in five studies conducted between 1984 and 2001. About 80% of the caffeine consumption was from the intake of coffee. Researchers propose that people who have the genetic variant for high-consumption of caffeine metabolize caffeine at a different rate when compared to those with the variant for low-consumption of caffeine. The two groups of people require different amounts of caffeine to maintain or achieve the physiological levels that can produce the pleasurable effects, tells Cornelis. “The study clearly shows that the genetic variations affect how our body processes caffeine," adds Cornelis.
Caffeine is known to affect a number of medical and physiological conditions including mood, sleep patterns, energy levels, and mental and physical performance. Further, products containing caffeine is implicated in a variety of medical conditions. “A study focusing on the effects of caffeine on cardiovascular system becomes hard when the metabolism of caffeine differs from person to person," Cornelis remarks.
This knowledge that caffeine intake depends on the genetic variation could be used to advance research and try to identify the group of population who are most susceptible to the effects of caffeine. According to Cornelis, more studies are required in this field and it is possible that more genes are linked with the processing of caffeine. This study published in the journal, PLoS Genetics, may be the first of its kind to show how genetics may be responsible for the differences in how people drink coffee.