Researchers at the university analyzed the health records and the self-reported coffee consumption of 347,077 people between the ages of 37 and 73 in the UK Biobank. The Biobank is a national and international health resource with unparalleled research opportunities, open to all bona fide health researchers.
The study found that people who drink one to two cups of caffeinated coffee a day had a lower risk of cardiovascular disease than people who drank decaf or no coffee at all. But for individuals who consumed six or more cups of caffeinated coffee a day, the risk of cardiovascular disease increased 22%. The researchers found no genetic cause for this increase.
This is the first time an upper limit has been placed on safe coffee consumption and cardiovascular health.
"In order to maintain a healthy heart and a healthy blood pressure, people must limit their coffees to fewer than six cups a day — based on our data six was the tipping point where caffeine started to negatively affect cardiovascular risk," Hyppönen said.
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Even though the research says five cups of coffee is permissible, Hyppönen said each person should know his or her own limit. If you begin feeling jittery, irritable or nauseated, she said, you might have reached your limit for the day.
The study was published in the American Journal of Clinical Nutrition. You can read it here.