Folks who chug lots of coffee may have their genetics to thank for their java cravings, a new study says.
Researchers have linked six genes to a person's coffee consumption. All of the genes are related to the body's response to caffeine, according to the study.
"These are genes that we previously would not have implicated with coffee, and they show that there is some genetic basis for our coffee consumption behavior," said lead author Marilyn Cornelis, a research associate in nutrition at the Harvard School of Public Health.
These genes could help explain why some people enjoy coffee more than others. "My response to a cup of coffee might be very different to someone else's response to the same cup," Cornelis said.
They also could explain the popularity of energy drinks and other products that contain caffeine, said Rachel Poole, a postdoctoral fellow at the Monell Chemical Senses Center in Philadelphia, a nonprofit scientific institute dedicated to research on the senses of taste and smell.
"In the past coffee and tea were the primary sources of caffeine worldwide. Now, there are many more products that contain caffeine -- energy drinks, flavored waters, gums," Poole said. "Therefore, it is important that we understand genetic factors underlying caffeine intake as caffeine consumption patterns have changed."
Coffee is one of the most popular beverages worldwide, according to background information in the study. In North America, people who drink coffee generally consume about two cups a day. In Europe, the average is about four cups daily, the study reports.
Previous research has linked regular coffee consumption to a reduced risk of Parkinson's disease, type 2 diabetes and liver disease, according to the study. However, not all research on coffee is positive. The beverage has also been implicated in cardiovascular problems and other health issues, the study reported.
Researchers discovered the six "coffee" genes after reviewing 28 previous studies on the genetic makeup of more than 120,000 coffee drinkers. They compared each person's genetics to how much coffee they said they regularly drink each day.
"Out of 2.5 million variants in the genome, we found a handful that were strongly linked to coffee consumption," Cornelis said.
Two of the genes are related to the way a person's body metabolizes caffeine, the study reports.
"Individuals that consume larger quantities of coffee may metabolize caffeine more quickly than others, and this could be due to their genetic makeup," Poole said.
Another two genes appear linked to the "kick" that a person receives from caffeine. These genes are tied to the brain's pleasure centers, and likely influence the amount of stimulation or enjoyment that caffeine provides, Cornelis said.
The final two genes "were really unexpected," Cornelis said. Those genes previously have been linked to metabolism of fats and sugars, but had not been suspected as influencing the body's response to coffee.
This indicates that the genes may impact the brain process that senses blood glucose levels, which may in turn influence a person's response to caffeine.
Poole warned that while these specific genes respond to caffeine, there likely are other factors that influence a person's love of coffee.
"It would not be correct to conclude that coffee consumption is driven solely by genetic responses to caffeine. There are many bioactive compounds in coffee that could determine coffee consumption," she said. "Furthermore, many people add milk and sugar to their coffee, and genetic factors underlying milk and sugar intake could play a role in coffee intake."
The next step in the research will be to examine the genes identified in this study and see if they impact the risk of certain diseases, Cornelis said.
The findings were published Oct. 7 in the journal Molecular Psychiatry.