April 8, 2011

DNA Determines Coffee Intake

According to new research, our own DNA is the single biggest factor in determining whether we go for that cup of coffee every morning.

Researchers, reporting their findings in the journal PLoS Genetics, believe they have found two genes that affect how quickly a person "metabolizes" the stimulant that makes him or her crave more or less coffee.

The new study found that people who carry a specific version of the two genes were much more likely to consume caffeine. Those genes identified were CYPIA2, previously linked to the metabolism of caffeine, and AHR, which helps to regulate CYPIA2.

"We know caffeine had an inherited component but for the first time we know specifically the major genes involved," Dr. Neil Caporaso, branch chief of genetic epidemiology at the National Cancer Institute and senior investigator for the study, told ABC News. "Genetic studies have identified many associations with diseases, but very few for diet agents."

Caporaso, co-author of the study, said it's an "incredible story"¦. People don't really suspect it, but genetics plays a big role in a lot of behaviors, such as smoking and alcohol consumption."

Caporaso and colleagues from the Harvard School of Public Health and the University of North Carolina, got their results from the genetic mapping of more than 47,000 Americans of European descent compiled from five different studies between 1984 and 2001. The analysis examined average caffeine consumption estimates -- when available -- for each participant's intake of coffee, tea, soda, and/or chocolate.

Gathering and combining the data, Caporaso and colleagues found that those who carried the highest-consumption version of the genes consumed, on average, and extra 40 milligrams of caffeine compared to those with the lowest-consumption genotype.

This closely equals the amount of caffeine found in a single can of cola, or in a third of a cup of coffee.

"The point here is that the way we drink caffeine is not just random," said Caporaso. "It's related to the genetic hand of cards you were dealt. And that means that now we can dissect people into fast metabolizers and slow metabolizers: people who have just one small coffee and feel well caffeinated for a day, and people who have two large ones and then another Coke a little later in the day to get the same effect," he added.

The study noted that 9 in 10 adults eat or drink caffeine on a regular basis and eight in 10 Americans who consume caffeine are coffee drinkers.

Caporaso noted that it was "astonishing" to find the two linked caffeine genes after searching over 300,000 genetic markers. And, since one gene regulates the other, "to find them both holding hands was amazing," he added.

"Caffeine is the most commonly consumed substance with important psychoactive properties," said Caporaso. "Just try skipping your coffee for two days! Knowing the specifics of the genetic influence on its disposition will jumpstart lots of studies."

The caffeine study provides "another block in building a picture of personalized medicine," Dr John Mulvihill, at the University of Oklahoma, told The Telegraph.

"Even though the general notion of having more or less tolerance to caffeine is not a new observation, the clinical utility of this work could eventually have to do with the fact that the genes implicated in caffeine metabolism are also involved in the metabolizing of other things," Mulvihill said.

Researchers hope to study why people react differently to caffeine and how the drug can impact other conditions like diabetes and heart disease.

"This is one of the most obvious examples of where we're going with personalized medicine," said Dr. Michael Watson, executive director of the American College of Medical Genetics. "We're able to look at the variations and the way people deal with drugs and the way they metabolize them."

"This is not something that just geneticists are going to be doing in the future," said Watson. "Once we figure it out, a person's primary care physician will use the information with their patients."


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