Researchers say they've discovered two gene variations that influence the metabolism of caffeine in the body and are associated with how much caffeine people consume, WebMD reported Thursday.
Both genes are possessed by all people, but a study of more than 47,000 middle-aged Americans of European descent found people with the highest-consumption variant for either gene consumed about 40 milligrams more caffeine -- about the equivalent of half a cup of coffee or one can of soda -- per day than people with the lowest-consumption gene varieties.
"There are hundreds of genes known for specific medical conditions -- for dietary consumption we know very little," study co-author Dr. Neil Caporaso of the National Cancer Institute told the BBC.
"Now, for the first time, we know specific genes that influence the amount of caffeine that individuals consume," he said.
This genetic knowledge could be used "to advance caffeine research and potentially identify subgroups, defined by genotype, of the population most susceptible to the effects of caffeine," said study co-author Dr. Marilyn C. Cornelis of the Harvard School of Public Health.
"More research on the precise function of these variants is needed, however, and there are likely more 'caffeine genes' to be identified."
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