Health benefits of coffee and a proposed warning label

Coffee cup and beans on wooden table. Top view.
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Faculty Editor, Harvard Health Publishing

Coffee is among the most popular beverages ever, enjoyed by millions of people worldwide each day. Estimates suggest that Americans consumed 3.4 billion pounds of coffee last year. When it comes to its health effects, coffee is also among the best studied beverages. How much is too much? Does coffee cause cancer? What is behind the proposed new warning label for coffee?

Fortunately, the news on coffee is mostly good. This includes a recent study that found coffee drinkers live longer, a conclusion that held up even for heavy coffee consumption (eight or more cups of coffee each day), and regardless of whether the coffee was caffeinated or not. And longevity was linked to coffee consumption regardless of what type of caffeine metabolism genes you carry. The authors concluded that the health benefits of coffee go beyond caffeine.

Prop 65 warning label

Perhaps you saw articles like this one describing an effort in California to require a notification to coffee consumers of a possible link to cancer. Here’s the reason: in 1986 California passed Proposition 65, which requires businesses to provide a warning label when exposing any consumer to any item on a long list of potentially harmful chemicals. Acrylamide is on that list, and coffee contains acrylamide, a chemical produced during the roasting process.

How worried should we be about acrylamide in coffee?

Nothing has changed in our understanding regarding the potential side effects of coffee, or its benefits. No study has convincingly linked acrylamide in coffee (or coffee in general) to one’s risk of cancer, and there is plenty of research. Many studies have explored whether there is a potential link between drinking coffee and cancer. Perhaps the most damning are ones (such as this one) suggesting hot beverages and foods may increase the risk of esophageal cancer. But that concern isn’t particular to coffee, and the specific temperature at which this risk appears has not been well defined.

The amount of acrylamide in coffee varies, and is quite small compared to amounts found to cause cancer in animals. In addition, there are other sources of acrylamide exposure no one is making a fuss over, including bread, potato chips, and breakfast cereals. It’s also found in cigarettes.

The challenge of proving a negative

The Los Angeles judge ruling on the new labeling requirement for coffee wrote that the coffee companies did not prove that acrylamide was safe. In essence, the judge was asking that the coffee makers prove a negative (the absence of risk), and that’s hard to do!

For example, if a particular food (or other exposure) is safe, studies finding no connection to harm can always be criticized — a different analysis, more time, or more study subjects could have led to different findings. Or, it might take a long and expensive study that hasn’t happened yet. For a particularly dangerous exposure (such as cigarette smoking), establishing a link is much easier. (As an aside: the difficulty proving a negative is a major reason that unfounded conspiracy theories persist.) The judge also discounted the extensive research linking coffee consumption to health benefits; exactly why he did is unclear.

While future research could find a link between coffee and cancer, there’s no particular reason to expect that to happen.

Health benefits of coffee

A partial list of potential coffee health benefits includes a lower risk of:

  • liver cancer (and perhaps colon cancer as well)
  • liver failure due to cirrhosis
  • dementia
  • type 2 diabetes (which accounts for more than 90% of all diabetes)
  • gout
  • death (as noted above, a number of studies have linked coffee consumption with living longer).

So, even if the trace amounts of acrylamide in coffee were found to increase cancer risk or cause other harms, these risks might be outweighed by the benefits of drinking coffee.

What’s next for coffee lovers?

Additional legal wrangling is expected, so it may be a while before California’s plans regarding warning labels for coffee are settled. In the meantime, you can take steps to limit your exposure to acrylamide by not smoking, eating less fried, burnt, or charred foods, and avoiding instant coffee. And perhaps we will discover ways of reducing or even eliminating acrylamide in the coffee roasting process. But it’s not clear that changing how coffee is roasted will actually improve your health. As is so often the case with potentially carcinogenic toxins, we’ll need additional research to determine whether the amount of acrylamide in coffee and other foods and drinks matters a little, a lot, or not at all.

(Reprinted with permission from Harvard Gazette.)


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