Welcome to the Great Debates, where we consider the greatest nutritional controversies of our time. Our goal isn't to tell you what to think or do, but rather to present both sides of hot-button issues, like coffee (is it good for you?) and breakfast (the most important meal of the day?). What's being said? Who's saying it? Then it's up to you to make your own decisions.
Coffee! Intoxicating miracle elixir, or carcinogenic poison in a paper to-go cup?
The relative merits of the stuff have been hotly contested for centuries. The following historical allegations have been made (in no particular order): coffee causes impotence, blindness, stunted growth, heart attacks, and may increase the risk of bladder cancer.
At the same time, coffee has been been credited with an equal and opposite list of potential health benefits, including (although again not limited to) increased life expectancy; decreased risk of certain cancers, type-2 diabetes, heart attacks (are you sensing some contradictions?), and strokes; lowered risk of depression (in women); and the ability to help undo liver damage.
And so what are we, coffee drinkers and non-coffee drinkers alike, to do? Should we stop drinking coffee if we drink it? Should we start drinking coffee if we don't?
In the interest of living our longest, fullest, and most caffeinated lives, let us examine the evidence, beginning with the positive.
Coffee Is Good: The Evidence
In the last year in particular, an onslaught of studies have come out suggesting that coffee may have so many possible health benefits that it's practically kale.
Coffee and Mortality
Coffee drinking was linked to a reduced risk of death from heart disease, stroke, diabetes, neurological diseases and suicide, although not from cancer.
The study, which followed more than 200,000 doctors and nurses for up to 30 years, found the association between coffee consumption and not dying stands even after controlling for "age, alcohol consumption, B.M.I. and other health and diet factors." It also holds true whether people drink caffeinated brew or decaf.
Still, in what will become a running theme here, the observational study doesn't prove that coffee is the cause of the mortality drop — only that the two factors are associated.
Coffee and Cancer
While that specific study did not show a link between between coffee and cancer, other studies do suggest moderate sipping won't cause cancer and may even help lower the risk of at least some cancers. This past spring, the World Health Organization's International Agency for Research on Cancer published a report, for which 23 international scientists reviewed more than 1,000 studies on the topic. Here'sthe New York Times, on the findings:
The agency said the evidence showed that drinking coffee was unlikely to cause several types of cancer, including breast, prostate and pancreatic cancers, and that it was associated with a lower risk of uterine and liver cancers. For 20 other types of cancer there was "inadequate" evidence of a link to cancer, said Dana Loomis, the deputy head of the agency's program that classifies carcinogens and the first author of the report.
Hurray! And while we're on the topic of cancer, here's even more to celebrate: Coffee has also been associated with a lowered risk of colon cancer recurrence — although again, it's not clear if that's because of the coffee, or because coffee-drinkers tend to be neurotic people more likely to be obsessive about their treatment plans — and a slightly reduced risk of melanoma. As usual, it's not yet clear if that's causation or correlation, but we'll take it! (Also, though, wear sunscreen.)
Coffee and Cirrhosis, Depression, Tinnitus, and Parkinson's
Another argument for the curative properties of the stuff: A recent study found that drinking coffee might help fend off cirrhosis, the kind of liver disease associated with alcohol, Reuters reported. In fact, the more cups of daily brew people drank, the more their risk seemed to fall. Refills for everyone!
If cirrhosis isn't your concern, perhaps depression is? Because a study out of the Harvard School of Public Health found that postmenopausal woman who drank four cups of caffeinated coffee a day (or more) had a lower risk of depression than women who drank a cup or less per week. (Note: The study doesn't prove cause and effect — only that there's a link.)
Suffering from tinnitus? Apparently, drinking roughly a cup of (caffeinated) coffee a day is associated with a 15 percent lowered risk of oppressive ear-ringing. Coffee drinkers also have lower rates of Parkinson's than their less-caffeinated peers.
Coffee Is Bad: The Evidence
"Bad" might be an overstatement here. There are the obvious potential side effects, none of which will come as a surprise if you've had a few cups too many — trouble sleeping, a spike in anxiety, a general jittery feeling — but there's not currently a whole lot of evidence that normal coffee is bad-bad. Even the USDA says moderate consumption (three to five cups per day, by their definition) is "not associated with increased long-term health risks," and, moreover, goes on to acknowledge "consistent evidence" of its assorted health benefits.
Still, to all roses, there are thorns, and coffee does indeed have downsides — at least for some people, and at least in some cases.
Coffee and Diabetes
While coffee may lower the risk of type 2 diabetes (see above), drinking caffeinated coffee is not necessarily great if you already have type 2 diabetes. Caffeine raises blood sugar, the AARP explains, which can make it harder to manage insulin levels. It can also raise blood pressure. Neither is an argument against coffee per se, but if you're concerned about either issue, switching to decaf could help.
Coffee and Heart Disease
Coffee could actually increase your risk of heart disease. But didn't we just say the opposite of that? Yes, yes we did. And that seems true for a lot of people.
But some studies have shown that in certain people — people with a specific, but relatively common genetic mutation that affects the breakdown of caffeine — two or more coffees a day might not be such a boon after all, according to the Mayo Clinic
Some early studies suggested that coffee might increase cholesterol levels in general, and LDL cholesterol levels — that's the "bad" kind — in particular, but the Harvard Health Letter, from Harvard Medical School, reassuringly explains that that's true only if the coffee is brewed using certain methods:
"… upon closer inspection, the bad news turned out to be not so bad, because the cholesterol-raising effect seems to be limited to coffee that hasn't been filtered, which includes Turkish coffee, coffee brewed in a French press, and the boiled coffee consumed in Scandinavia."
Paper filters it is! (That said, a 2011 study showed cotton-nylon cloth filters or metal mesh filters are also pretty effective.) Of course, the complicating factor (there is always a complicating factor) is that LDL cholesterol might also have some anti-cancer, pro-liver health benefits, but if cholesterol is a concern, it is possible you should consider switching away from your French press.
In Conclusion: Your Decision
Should you drink coffee? It's complicated. The general consensus as of now seems to be that yes, if you already drink coffee and enjoy drinking coffee, you should feel free to continue drinking coffee. But if you don't drink coffee, you probably don't have to start. "We'd need a different level of evidence to recommend it to people," Dr. Rob van Dam, an adjunct associate professor of nutrition and epidemiology at Harvard University, told the Times earlier this year.
In conclusion, do what you want — at least, for now.
Have your own thoughts on the matter percolating? Share them in the comments!