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Coffee is powerful stuff. Researchers discovered earlier this year that just a whiff is enough to increase the body’s arousal levels, helping jonesers wake up and feel focused. Yet purported links to cancer, poor heart health, and shorter lives have percolated for decades. Now, better-brewed studies are debunking the previous bad news and linking coffee — even several cups a day — to specific health benefits and longer life.
One new study revealed that, contrary to prior research, drinking coffee isn’t thought to stiffen the arteries, which can force the heart to work harder and lead to a heart attack or stroke.
Researchers pored through a database of 8,412 people who had MRI heart scans and other cardiovascular tests and who answered questions about their coffee consumption. They found there was no difference in the stiffening of arteries among the people who said they had less than a cup a day versus those who drank one to three, or even four to five cups. Several people in the study reported drinking more than 25 cups per day — which generated a flurry of media coverage — but those people were excluded from the study.
“Whilst we can’t prove a causal link in this study, our research indicates coffee isn’t as bad for the arteries as previous studies would suggest,” says study team member Kenneth Fung of Queen Mary University of London. However, he cautions: “The coffee consumption in this study is self-reported, and so a limitation in this study is that the real intake could be over- or under-reported.” The research was presented on June 3 at a meeting of the British Cardiovascular Society.
Looking at the latest research, coffee seems to be somewhere between relatively benign and beneficial for most healthy adults.
A separate study published in the journal JAMA Internal Medicine last year, which relied on the same dataset used by Fung’s team, “suggests a lower risk of death was associated with drinking more coffee, including among coffee drinkers who have eight or more cups per day.”
A 2017 review of 201 coffee studies and 17 clinical trials, published in The BMJ, found coffee was “associated with a lower risk of several cancers, including prostate, endometrial, skin and liver cancer, as well as type 2 diabetes, gallstones, and gout.” Above that, the researchers discovered positive effects on brain health: Coffee consumption was linked to a lower risk of Parkinson’s disease, depression, and Alzheimer’s disease.
Looking at the latest research, coffee seems to be somewhere between relatively benign and beneficial for most healthy adults. So why has it gone from pure vice to potential virtue?
It’s the study design: Most older studies linking coffee directly to heart disease, a variety of cancers, and overall increased risk of death didn’t account for other factors, such as that coffee drinkers might be more likely to smoke or drink excessively, according to the Mayo Clinic. Many studies simply had weak methodology, says Dr. Robert Shmerling, a practicing physician and editor at Harvard Health Publishing.
In 2016, the World Health Organization removed coffee from its list of potentially carcinogenic foods, based on the evidence for coffee’s benefits, and lack of evidence for serious risks. That’s convenient, since nearly two-thirds of Americans drink it daily, according to the National Coffee Association.
Researchers are still figuring out where coffee’s health benefits come from. But, surprisingly, they’ve ruled out a connection to caffeine. A double-shot of research, reported in a 2017 issue of Annals of Internal Medicine, linked coffee — regular and decaf — to longer life and reduced risk of death from all causes.
One of the studies, billed as the largest of its kind, looked at coffee consumption and mortality among 521,330 people across Europe. The researchers discovered the following:
“Higher coffee consumption was associated with a lower risk of death from any cause, and specifically for circulatory diseases, and digestive diseases,” said lead author Marc Gunter, a nutrition expert at the International Agency for Research on Cancer. “Drinking more coffee was [also] associated with a more favorable liver function profile and immune response,” Gunter says.“Importantly, these results were similar across all of the 10 European countries, with variable coffee drinking habits and customs.”
The other 2017 study made a similar analysis of more than 215,000 people, but expanded the heretofore limited ethnic breadth of coffee research: “Drinking coffee was associated with a lower risk of death due to heart disease, cancer, stroke, diabetes, and respiratory and kidney disease for African-Americans, Japanese-Americans, Latinos and whites.”
“This study is the largest of its kind and includes minorities who have very different lifestyles,” says lead author Veronica Setiawan, an associate professor of preventive medicine at the University of Southern California’s Keck School of Medicine. “Seeing a similar pattern across different populations gives stronger biological backing to the argument that coffee is good for you whether you are white, African-American, Latino or Asian.”
Setiawan, who enjoys a cup or two a day, speculates on why coffee seems to be good for us:
“Coffee contains a lot of antioxidants and phenolic compounds that play an important role in cancer prevention,” she says. “Although this study does not show causation or point to what chemicals in coffee may have this ‘elixir effect,’ it is clear that coffee can be incorporated into a healthy diet and lifestyle.”
Antioxidants and other compounds in coffee have, in fact, been linked to reduced inflammation, as free radicals in the body are tamed, possibly lowering the risk of many illnesses. However, specific research on these mechanisms — and thus why coffee appears to be beneficial — remains elusive.
Coffee is not without risks. It harbors more than 1,000 chemicals, many of which aren’t well studied. Caffeine is a powerful stimulant that can cause “nervousness, irritability, trembling, palpitations, flushing, and heartbeat irregularities” in some people, says Graham Davey, a professor of psychology at the University of Sussex. There are conflicting views on whether caffeine is truly addictive, but stopping a heavy coffee habit can bring on headaches.
Caffeine, especially when consumed in the evening, can also impair sleep, and poor sleep is associated with increased risk of heart disease, depression, and other ills.
Coffee does not stunt growth, but given its strong stimulant effects, experts agree it’s bad for kids.
Pregnant women are advised to cut out coffee because it can cause low birth weight. There are also hints that too much coffee might contribute to osteoporosis in women, but the link is not conclusive.
Research suggests that coffee does raise blood pressure in people not used to it, but not in habitual coffee drinkers. Oh, and coffee does not stunt growth, but given its strong stimulant effects, experts agree it’s bad for kids.
For otherwise healthy adults, the U.S. government’s Dietary Guidelines recommend that “moderate coffee consumption (three to five 8-oz cups/day or providing up to 400 mg/day of caffeine) can be incorporated into healthy eating patterns.”
Since 8-ounce cups are so yesterday, here are some comparisons:
Researchers don’t suggest coffee lovers up their consumption, or that non-coffee-drinkers should start up. And exactly zero scientists recommend 25 cups a day.
“I drink a couple of cups of coffee most days,” Erikka Loftfield, whose JAMA study found lower mortality even among people who drink eight or more cups daily, says in an email. “And while I think our study and others offer reassurance to coffee drinkers, I also think that eating a healthy diet and staying physically active are more important for maintaining health and promoting longevity.”