New research from The New England Journal of Medicine suggests coffee may help you live longer. A study of more than 400,000 men and women links coffee with a lower risk of death
The study, described as the largest of its kind, found that coffee drinkers had a lower risk of death from heart disease, respiratory disease, stroke, accidents and injuries, diabetes, and infections, but not from cancer. Researchers observed these results after accounting for the effects of other risk factors for dying, such as smoking and drinking alcohol.
The scientists examined the connection between drinking coffee and death among more than 400,000 men and women in the National Institutes of Health-AARP Diet and Health Study. Participants lived in six scattered states and the Atlanta and Detroit metropolitan areas. At the beginning of the study, they were 50 to 71 years old and had not had cancer, heart disease, or stroke.
Between 1995 and 1996, the men and women completed a comprehensive questionnaire assessing their diet and lifestyle. Nine out of 10 study participants drank coffee, and few of the coffee drinkers said they also drank tea, the focus of a future analysis, says researcher Neal Freedman, PhD, of the Division of Cancer Epidemiology and Genetics at the National Cancer Institute.
Freedman and his collaborators then followed the people in the study until the date they died or Dec. 31, 2008, whichever came first.
Compared to people who drank no coffee, coffee drinkers who downed three or more cups a day had about a 10% lower risk of death overall and a lower risk of dying from each of a variety of leading killers. Cancer was the only exception.
Among women, coffee drinkers and non-drinkers were equally likely to die of cancer. Among men, there was only a slight connection between heavier coffee drinking and increased risk of dying from cancer.
The study findings should be reassuring to people who drink coffee, one of the most popular beverages in the United States and worldwide, Freedman says. "There's been a concern for a long time that coffee drinking might increase the risk of death."
But he's not advising anyone to start drinking coffee on the basis of his results.
"Coffee is a complicated beverage," Freedman says, noting that it contains 1,000 different compounds, most of them little-studied.
Besides, because study participants weren't assigned to drink coffee or not drink it, the researchers can't be sure what caused the lower death rate -- the beverage itself or some unmeasured characteristic of the people who chose to drink it. This type of study can show the association, but it can't say that coffee caused people to live longer.
If you are thinking about starting to drink coffee, talk to your doctor about whether you might have any reason not to, Freedman says, adding that "there are some data that show coffee might cause a short-term increase in blood pressure."
Although their study can't prove that coffee itself lowers drinkers' risk of dying, Freedman and his colleagues speculate about how it might. Caffeine probably is not a factor, he says, because death rates linked to decaf, preferred by a third of the coffee drinkers, were similar to those associated with caffeinated. But other compounds in coffee, such as antioxidants, might be important, the researchers write.
The researchers note several limitations of their study. For one, they lacked information about how the coffee was prepared, which could affect its compounds. And they asked about coffee consumption only once at the beginning of the study, but participants' habits might have changed over time.
"People do quit drinking coffee as they get older, or they switch to decaf ... because they don't sleep as well or they get palpitations," says Arthur Klatsky, MD, senior consultant in cardiology for Kaiser Permanente of Northern California. Klatsky was not involved with Freedman's research but has conducted his own studies of coffee and health.
"It's a big study with a remarkable result," Klatsky says. "It's a little bit hard to believe that coffee drinking is protective against all those different causes of death."
His own research found no such connection overall. Perhaps Freedman's study would have come up with different findings if it had enrolled a younger and more racially diverse population, Klatsky says.
While Freedman's team seems puzzled by the link between coffee drinking and a lower risk of death from accidents and injuries, including suicide, Klatsky says that one potential link "to me makes a little bit of sense." In this case, it probably is the caffeine, he says. "In people who are caffeine-addicted, it certainly brightens mood and staves off fatigue."