In a 10-year U.S. study, people who drank coffee regularly were less likely to die of many causes, including heart disease and diabetes, than those who didn't drink coffee at all.
The more coffee study participants consumed, the lower their risk of dying, and decaf drinkers showed a similar pattern.
"Coffee contains numerous biologically active compounds, including phenolic acids, potassium, and caffeine," said lead author Dr. Erikka Loftfield of the National Cancer Institute in Rockville, Maryland.
Many studies have found that coffee consumption is associated with lower risk of overall and heart-related mortality, Loftfield told Reuters Health by email.
The researchers used data from a previous study on 90,317 adults without cancer or history of cardiovascular disease who were followed from 1998 through 2009. They had reported their coffee intake, along with other dietary and health details, at the start of the study.
By 2009, about 8,700 people had died. After accounting for other factors like smoking, the researchers found that coffee drinkers were less likely to have died during the study than nondrinkers.
The risk of death was lowest for those who drank four to five cups of coffee per day. A similar association was seen among drinkers of decaffeinated coffee as well, according to the results in American Journal of Epidemiology.
Coffee drinkers had a reduced risk of death from heart disease, chronic respiratory diseases, diabetes, pneumonia and influenza and suicide, but not cancer, the researchers found.
"Although coffee drinking has also been inversely associated with incidence of certain cancers, like liver, in epidemiological studies, we did not observe an association between coffee and overall cancer mortality," Loftfield said. "This may be because coffee reduces mortality risk for some cancers but not others."
People who consumed two to three cups of coffee per day had approximately an 18 percent lower risk death during follow-up compared to those who reported drinking no coffee, she said. Drinking up to five cups per day, or 400 milligrams of caffeine per day, is not associated with any long-term health risks, Loftfield added.
Moderate caffeine intake, up to 200 milligrams per day, is even safe for pregnant women, according to a statement by the American College of Obstetricians and Gynecologists.
"There is an accumulating number of studies of very high quality that show that people who drink more coffee tend to have better health outcomes," said Dr. Marc J. Gunter of Imperial College London, who was not part of the new study.
"Coffee drinking is correlated with other health behaviors," and those who drink it regularly may have other healthy habits, like exercising and keeping to a healthier diet, though the researchers tried to account for those other factors, Gunter told Reuters Health.
The study doesn't prove that coffee extends life.
"You could argue that people who are already sick might not be drinking as much coffee," Gunter said.
But coffee may also have a direct effect on inflammation or cardiovascular health, he said.
"It doesn't seem to do you any harm, if you like drinking coffee then carry on," Gunter said.
Coffee can be part of a healthy, balanced lifestyle, and it may even do some good, though we can't yet recommend than non-drinkers adopt the habit for health reasons, he said.