It’s been a good couple of weeks for coffee. First, the panel of experts assigned the job of revising the U.S. Dietary Guidelines for Americans essentially gave the all-clear to drinking a few cups of the caffeinated beverage daily.
“Strong evidence shows that consumption of coffee within the moderate range (3 to 5 cups [per day] or up to 400 milligrams [per day] caffeine) is not associated with increased risk of major chronic diseases, such as cardiovascular disease (CVD) and cancer and premature death in healthy adults,” they wrote. (Note: The exception was pregnant women, who the panel said should limit their daily caffeine intake to 200 milligrams a day.)
This is the first time over the 30-plus-year history of the guidelines that health officials have addressed the issue of coffee.
Then, this week, came a study from Korea that seemed to be suggesting moderate coffee consumption helps protect against clogged arteries (atherosclerosis) and, thus, heart attacks.
Seemed is, of course, the operative word here. For, as medical reporter Larry Husten explains in an online column for Forbes, the Korean study was observational, which means that its findings cannot be interpreted as demonstrating any kind of causal connection — good or bad — between coffee and heart disease.
“Although the researchers attempted to adjust for important differences between the groups, this effort is ultimately impossible when studies deal with real people in the real world and not mice living in cages,” Huston writes. “I would be willing to bet a whole lot of money that people who drink different amounts of coffee differ in all sorts of extremely important ways (psychological, physical, environmental, social). There is no way to measure or adjust for most of these factors. Coffee — along with alcohol, exercise, diet, and so many other “lifestyle” factors — is how we define ourselves.”
But that didn’t stop some media outlets from confidently declaring the study had demonstrated that coffee has direct health benefits: “Coffee Prevents Clogged Arteries,” “Drinking Three Cups of Coffee a Day Reduces Risk of Heart Attacks,” and “Coffee Can Save You from Heart Attacks Aside from Keeping You Awake.”
As Huston points out, the authors of the new study were much more cautious than the media about their research’s conclusions. “Our findings are consistent with a recent body of literature showing that moderate coffee consumption may be inversely associated with cardiovascular events,” the authors wrote. They also stressed that “further research is warranted to confirm our findings and establish the biological basis of coffee’s potential preventive effects on coronary artery disease.”
One of the authors of the study told Huston that he was concerned that the media was exaggerating the findings. No one at this point should be drinking coffee to prevent heart disease, the researcher explained, but, on the other hand, people who already drink coffee in moderation may find some reassurance in the study’s findings that coffee is not associated with an increased risk of heart disease.
A matter of dose
And that’s pretty much what the U.S. Dietary Guidelines experts say in their new recommendations.
They, too, don’t claim that coffee is good for you. In other words, no one should start consuming coffee to prevent cardiovascular disease. Indeed, if you want to take action to protect your heart, go for the lifestyle behaviors with a proven track record: regular exercise, not smoking, eating a heart-healthy diet and maintaining a healthy weight.
What the experts are saying, however, is that if you’re already drinking coffee (in moderation), you don’t necessarily need to stop.
Of course, this advice is for adults. Furthermore, the “moderate consumption” recommendations are really about caffeine, not about cups of coffee. Sodas and energy drinks, for example, often contain plenty of caffeine as well.
And then there’s the matter of cup size. The panel of experts’ “3 to 5 cups per day” recommendation refers to 8-ounce cups of coffee containing an estimated 100 milligrams of caffeine each. But the smallest cup of coffee offered in most coffee shops starts at 12 ounces, and a single 20-ounce cup of coffee from Starbucks contains 415 milligrams of caffeine.
So start doing the math. For help with figuring out the caffeine content in your favorite coffee (and other foods and drugs), use this handy listing from the Center for Science in the Public Interest. (Full disclosure: I worked for CSPI many years ago.)