Heavy Coffee Drinking Tied to Shorter Lives for Younger Adults in Study
But experts say research has many limitations
Lower levels of coffee-drinking didn't seem to affect mortality. "We were honestly hoping to find that low amounts of coffee were beneficial," said Lavie, "and we were hoping no dose was toxic."
Many questions remain unanswered, however, and the study authors said further research is needed. Lavie said it's possible that coffee might contribute to cancer, but researchers can't confirm that unless they dig deeper to see what killed participants in the study. It's also possible that certain genetic factors put heavy coffee drinkers at greater risk, the study suggests.
Rob van Dam, an associate professor at the National University of Singapore, said the study has significant shortcomings. Among other things, he said, it didn't examine dietary habits or look at causes of death in depth. "There have been several previous studies on this topic, and recommendations about coffee consumption should consider the totality of the evidence rather than only the results from a single study," he said.
Rachel Huxley, chair of epidemiology at the University of Queensland in Australia, cautioned that smoking -- much more common among heavy coffee drinkers than others -- may have thrown off the results by contributing to death rates. The study results don't do enough to take this into account, she said.
Huxley added that previous research as a whole suggests that the level of coffee consumption in question actually helps people live longer.