Coffee drinkers live longer, according to two large-scale studies released Monday that add to extensive research indicating coffee consumption is associated with better health.
The studies examined the health histories of hundreds of thousands of people who were tracked over many years. They found that coffee-drinking reduced the risk of various diseases among people from several ethnicities, and this effect was seen in drinkers of regular or decaffeinated coffee. And the more coffee consumed, the greater the benefit.
These are observational studies, not controlled clinical trials. So while they demonstrate an association, they don't prove cause and effect. And it's possible that extremely high levels of coffee consumption may produce other undesirable effects besides caffeine jitters.
But at the least, researchers said the latest evidence reinforces a large body of previous reports indicating there's no harm from most people's coffee consumption habits, and that it might very well benefit people's health.
Both of the new studies were published in the Annals of Internal Medicine. They asked participants about whether they drank coffee, and if so, how much. Participants were also asked about habits that influence health, such as smoking, exercise and heart disease.
One study was led by Veronica W. Setiawan of the University of Southern California. Funded by the National Cancer Institute, it examined coffee-drinking habits among more than 180,000 whites, African-Americans, Latinos, Japanese-Americans and native Hawaiians. They were followed for an average of 16 years. Go to j.mp/coffeeusc for the study.
The other was performed by European scientists from Imperial College London and the International Agency for Research on Cancer, led by Marc J. Gunter of the IARC. It examined coffee-drinking among more than 520,000 adults from 10 European countries. Go to j.mp/eucoffee for the study.
The study led by Setiawan found those drinking one cup of coffee daily had a 12 percent lower risk of death from heart disease, cancer, stroke, diabetes, respiratory and kidney disease. For those drinking 3 cups a day, the risk reduction rose to 18 percent.
In previous studies, the great majority of those examined were white, meaning that environmental and lifestyle differences among ethnicities could have confounded the results. But her study found these benefits to occur regardless of the ethnicity studied.
The study led by Gunter likewise found a lower death risk from various ailments, including digestive, circulatory and liver disease. The relationship was the same regardless of country, the study found. It was funded by the European Commission Directorate-General for Health and Consumers and International Agency for Research on Cancer.
A Good Buzz
The studies make a significant contribution to knowledge about coffee and health, said Peter Adams, professor of the Tumor Initiation and Maintenance Program at Sanford Burnham Prebys Medical Discovery Institute.
"It's good to know that not everything that gives you a buzz is bad for you," Adams said by email.
"These two publications extend the findings of previous studies indicating the apparent benefits of coffee drinking," he added. "While the data across these and previous investigations seems consistent and compelling, to be really convincing it is important to figure out how it works.
"As the authors note, coffee is a complex concoction, and caffeine itself does not seem to be responsible. Coffee does contain many other candidate molecules, for example anti-oxidants."
"However, recent studies have challenged the view that anti-oxidants are always beneficial. Oxidants may not cause aging as previously thought, and anti-oxidants can even help cancer cells to survive!"
"So until we figure out how it works, you can keep drinking coffee and stay off the expensive anti-oxidants from the pharmacy," he said.
Coffee is most renowned for its stimulant effect, provided by caffeine. However, individuals respond differently based on their genetics. Some people are metabolically fast at breaking down caffeine, others metabolize it more slowly.
Among the slow metabolizers, Ozzy Osbourne, the heavy metal legend and lead singer of Black Sabbath, which recently completed what the band billed as its final tour.
This has health consequences. One of the few studies that showed some harm in coffee found that slow metabolizers who drank four or more cups of regular coffee a day experience a 36 percent greater risk of nonfatal heart attacks.
However, fast metabolizers who drank that much coffee had a lower risk of heart attacks. The presumptive explanation is that the non-caffeine components of coffee exert beneficial effects, and fast metabolizers clear caffeine quickly enough to avoid harm from an excessive dose.
The coffee tree is believed to have originated in Ethiopia. The beans were originally eaten for energy before the art of brewing the beverage was discovered. About 1,000 years ago, its use was first described in writing by Avicenna, the medieval Persian physician/philosopher.
Coffee's use spread throughout the Moslem world in the next few centuries. The first coffee houses opened in Istanbul and other parts of the Ottoman Empire. It gradually became popular in Europe, and gained predominance in the nascent United States as a patriotic alternative to drinking tea.
Since then, coffee-drinking has become such a widespread daily ritual around that world that it has been taken for granted. In recent decades, scientists have made growing efforts to understand what coffee does for us -- or to us.
Harvard University scientists have carried out a large number of these studies.
In 2001, Harvard researchers reported that drinking caffeinated coffee greatly reduced the risk of developing Parkinson's disease, cutting rates nearly in half.
A 2011 Harvard study found that men who regularly drink coffee have a lower risk of a lethal form of prostate cancer.
Two studies released by Harvard in 2012 found coffee consumption reduced risks of heart failure and skin cancer. The heart failure study found the benefits peaked at two cups per day, but declined with more coffee. At five cups a day, the benefit vanished and a potential for harm emerged.
There's plentiful research on coffee and health outside of Harvard. For example, a 2014 study from the National Cancer Institute reported that drinking coffee, both caffeinated and decaffeinated, may protect liver health.
Another study conducted in 2014 in Singapore found that coffee consumption reduces the risk of death from non-viral liver cirrhosis by 66 percent.
Before the recent slew of research, coffee had something of a bad reputation, according to an article on the Mayo Clinic website by Dr. Donald Hensrud.
"Why the apparent reversal in the thinking about coffee? Earlier studies didn't always take into account that known high-risk behaviors, such as smoking and physical inactivity, tended to be more common among heavy coffee drinkers," Hensrud wrote.
But these benefits come with some risks, he added. High consumption of unfiltered coffee is associated with mild elevation in cholesterol levels. And some studies have found that drinking two or more cups of coffee a day increases heart disease risk in people with a common mutation that slows caffeine metabolism.
In other words, easy on the java, Ozzy.
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