If you've ever wondered why you go through several cups of coffee a day while your best friend stops at two, researchers may have found the answer — and it doesn't have to do with the amount of sleep you get.
According to researchers at University of Edinburgh, the amount of coffee we consume may actually be linked to our genetics. The study, published in the journal Scientific Reports, found that people with a DNA variation in a gene called PDSS2 tend to drink fewer cups of coffee than those who did not carry the specific variant. The researchers said that the gene might reduce cells' ability to break down caffeine, causing it to stay in the body longer.
The study examined the genetic makeup of a little over 1,200 people living in Italy and asked participants to complete a survey that included a question about how many cups of coffee they drank daily. The researchers found that people with the DNA variation in PDSS2 tended to consume fewer cups of coffee than people without it. On average, those who carried the variation had around one more cup of coffee per day than those who did not.
To confirm those findings, the researchers also replicated the study on another group of more than 1,700 people in Netherlands. The results were similar, although the effect on the number of cups of coffee people drank was slightly lower, a finding that researchers attribute to a difference in the type of coffee people are drinking. People in Italy tend to drink small cups of espresso, versus the larger cups containing more caffeine that are more common in Netherlands.
Nicola Pirastu, MD, the study's author, admitted that his team would have to expand the study to a larger sample to confirm the discovery, but said in a press release, "The results of our study add to existing research suggesting that our drive to drink coffee may be embedded in our genes."
Previous studies have suggested a link between coffee and genetics, though this is the first to identify a specific genetic variant.
So the next time someone judges you for that fourth cup of coffee, just blame it on your genes.