People under 55 who drink an average of more than than four cups of coffee a day raise the risk of dying from all causes, according to a study published in the journal Mayo Clinic Proceedings.
Researchers led by Steven Blair at the University of South Carolina found that people aged under 55 who drank more than 28 cups a week saw a 56% increase in death from all causes.
The study analyzed medical and personal history questionnaires filled out by a total of 43,727 participants (33,900 men and 9,827 women) aged 20 to 87 between 1979 and 1998.
After a typical follow-up period of 17 years, more than 2,500 participants had died.
Xuemei Sui, a co-author on the study, noted that the " exact mechanism between coffee and mortality still needs clarification" but noted that coffee has the potential to " stimulate the release of epinephrine, inhibit insulin activity, and increase blood pressure."
Sui added that related vices, such as heavy drinking, may play a part.
"Heavy coffee consumption behavior might cluster with other unhealthy behaviors such as sleeping late, and eating a poor diet," Sui said in a statement.
Joseph Jebelli of The Guardian notes the study found that those who drank larger amounts of coffee were more likely to smoke and had less healthy lungs and hearts.
The study concluded: " On the basis of these findings, it seems appropriate to suggest that younger people avoid heavy coffee consumption (ie, averaging >4 cups per day). However, this finding should be assessed in future studies of other populations."
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