Health benefits of coffee and a proposed warning label

Robert H. Shmerling, MD

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.

Comments:

  1. cherry zhou

    Coffee Drinking has no doubt more benefits than disadvantages. I get it you have posted this article in favor of coffee drinking, but don’t you think the article would have been much better if you had mentioned the potential side affects as well?

    Cherry Zhou,

  2. Federico

    Dr. Schmerling

    Thanks for the article, very interesting and also clear on the coffee benefits. Just one question: Why do you state consumers should avoid instant coffee?

  3. J W

    coffee drinkers tend to be white collar professionals, they have better health care and other health habit, thus lives longer, need have better control groups for these studies.

  4. Cody Phillips

    Nice article on a salient topic.

  5. John

    The tone of this article seems a little skewed: it appears to undermine the studies on the potential harmful effects of coffee as not convincing because such links have not been proven, but then it seems eager to tout the health benefits of coffee using studies that likely have the same difficulty proving causality. Hence, it is important to highlight that in spite of the rhetoric that there is mostly good news about drinking coffee and that there is no reason to expect any links to cancer, the author can only speak of the “potential” health benefits of coffee and that the risks of coffee “might” be outweighed by the benefits. There are likely both benefits and hazards to be found in coffee, and it is still too early to be more dismissive of one side for the other.

  6. Dwight Oxley

    Excellent article.

  7. William (Bill) Murray

    Dr. Schmerling –

    Thank you for this excellent, succinct, and very clear summary of the situation regarding coffee, health, and California’s Proposition 65.

    I would only add that – perhaps in part due to clear-eyed assessments such as yours – the California regulator, OEHHA, is considering adopting a new rule which would eliminate the need for “coffee and cancer” warnings pertaining to acrylamide and other substances. The rationale for this change, according to the regulator, very closely tracks your own assessment.

    California authorities are currently in a public-input-phase of the process, which will end on August 30th of this year. With “science” on the side of this proposed change, there is an opportunity for the State’s decision-making process to be guided by the substantial body of independent research into coffee and health, and not by a legalistic interpretation of the statute.

    Sincerely,

    N.B. I am President of the National Coffee Association.

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