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Don’t worry about coffee’s cancer risk — or its health benefits

Don’t worry about coffee’s cancer risk — or its health benefits


Don’t drink coffee because it may help you live longer. Do it because you enjoy it.

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Photo by Amelia Holowaty Krales / The Verge

A ruling from a Los Angeles judge last week now means that in California, coffee companies like Starbucks must warn customers of a potentially cancer-causing chemical found in coffee. Naturally, this gave jitters to coffee makers and coffee drinkers alike — and renewed a centuries-old debate: Is coffee bad for you?

A nonprofit group, the Council for Education and Research on Toxics, sued 91 coffee companies for not warning consumers about a particular chemical produced when coffee beans are roasted. The chemical, called acrylamide, can also be found in some foods and cigarette smoke. Though it’s been shown to up the risk of various types of cancer in rats and mice — at least when they’re exposed to high doses — no such link has been confirmed in humans, according to the American Cancer Society.

“I’m not the least concerned about coffee being a problem for causing cancer.”

The coffee companies, which included Starbucks, said there isn’t enough acrylamide in the coffee to harm consumers. But Superior Court Judge Elihu Berle ruled that the coffee companies didn’t show that acrylamide was present at safe levels; they also didn’t show that drinking coffee has benefits, according to the Associated Press. The case isn’t over: No one has yet determined how much money the coffee companies will pay. But it’s the latest example of a judge being called to weigh in on scientific matters; the same is happening with climate change and even researchers trying to take down their own critics.

In this case, the ruling was probably an overreaction, says John Ioannidis, a professor of medicine, health research, and policy at Stanford University. “I’m not the least concerned about coffee being a problem for causing cancer,” Ioannidis says in an interview. The amounts of acrylamide people are exposed to in their coffee are so low that it’s hard to say it’d cause cancer, he says. “Among the zillions of things that surround us,” Ioannidis says, coffee is “among the most safe in terms of cancer risk.”

Joseph Galati, medical director for the Center of Liver Disease and Transplantation at The Methodist Hospital in Houston, agrees. “I really do not believe that there’s any validity to this,” he says. People tend to gravitate towards stories about coffee causing cancer since drinking coffee is part of so many people’s routines. “We make a big hoopla about it,” Galati says, but “at the end of the day, it is really meaningless.”

Photo by Amelia Holowaty Krales / The Verge

In fact, many studies have shown that drinking coffee might actually protect people from developing prostate and liver cancer, melanoma, and a type of cancer in the lining of the uterus, according to a huge review of the scientific literature published last year in The British Medical Journal. For certain types of cancer, like colon cancer, the evidence is a little less clear, says Syed Kazmi, assistant professor at UT Southwestern Medical Center and colon cancer expert. Some studies show that drinking coffee might protect people from getting colon cancer, while others don’t see that association. But research suggests that coffee drinkers who are diagnosed with colon cancer live longer than cancer patients who don’t drink coffee, Kazmi says.

It’s not just cancer, either. Drinking three to four cups of joe a day might lower your risk of dying of heart diseases, such as coronary heart disease, congestive heart failure, and stroke, says Donna Arnett, dean of the University of Kentucky College of Public Health and former president of the American Heart Association. There also seems to be no link between coffee intake and high blood pressure or irregular heart rhythm, she says. Some studies have even found that drinking coffee may reduce your risk of dying of an early death from any disease, by as much as 64 percent. How exactly coffee helps us out is unclear: It could be that coffee has anti-inflammatory properties, Galati says, or that it is a good source of antioxidants, which protect cells from damage.

As good as these findings sound, you’d be wise to be skeptical of them, says Ioannidis. Many of these studies are observational; they rely on participants to accurately report their own eating, drinking, and lifestyle habits over a long period of time. That leaves a lot of room for error. People may not remember how much coffee they drink, or they may not report some behavior, like smoking, because they’re ashamed of it. Plus, there are so many factors that affect your health, and whether or not you develop cancer, and observational studies can’t really account for all of them. “It’s a complete mess and to be honest, I think these studies are getting nowhere and we should just quit doing them,” Ioannidis says.

“I wouldn’t be surprised, actually, if there’s just no major benefit like there’s no major harm.”

To really find out if coffee is beneficial, researchers should conduct randomized trials where thousands of participants are either assigned to a coffee-drinking group or a no-coffee group, and followed for at least five years, Ioannidis says. But Arnett says that in our society, where coffee is so prevalent, it’d be really hard to conduct such a study. If a coffee drinker is randomly assigned to the no-coffee group, will that participant really give up coffee for five years? “I’m not sure that a randomized controlled trial would be feasible,” Arnett says.

Even without those kinds of rigorous studies, drinking coffee is definitely not something you should worry about, Ioannidis says. (The US dietary guidelines say it’s totally fine to guzzle up to five cups of joe a day.) Maybe just don’t drown it with sugar and cream, Kazmi says. Plus, know your limits: If you’re very sensitive to caffeine and downing an espresso at 4 PM will keep you up all night, don’t do that. For people who have migraines, a little coffee can help stave off headaches, but too much caffeine can actually trigger them.

Ioannidis says that we may never know how coffee really affects our health. “I wouldn’t be surprised, actually, if there’s just no major benefit like there’s no major harm,” he says. So if you’re a coffee lover, there’s no need to change your habits. But don’t drink coffee because it may help you live longer. Do it because you enjoy it.