In March 2018, a judge in Los Angeles ruled that coffee sold in California must carry a warning label, based on Proposition 65, which requires companies to alert consumers about products containing any of a growing list of chemicals (now more than 850) that could possibly cause cancer or birth defects. The coffee industry is fighting the decision. The chemical in coffee is acrylamide, which we first wrote about in 2002. That was when Swedish researchers caused an uproar by reporting that fried or baked starchy foods like French fries, crackers, potato chips, and even bread and breakfast cereals contain the compound, which they said may cause cancer.
For those of you who don’t live in California, Prop 65 (formally called the Safe Drinking Water and Toxic Enforcement Act of 1986) has been controversial from day one. Countless products carry the warning label, which overall has helped consumers make safer choices, though the ubiquity of the warnings makes it hard to distinguish genuine risks from trivial ones. For some labeled compounds, including acrylamide, the evidence of carcinogenicity for humans is open to debate. Prop 65 lawsuits are a big business. And what happens in California often affects the rest of the nation, as companies try to reformulate their products to avoid having to add a Prop 65 warning.
Acrylamide forms during frying, grilling, baking, roasting, and toasting, when the amino acid asparagine (notably in potatoes and grains) reacts with naturally occurring sugars, a reaction that gives the foods their brown color, crusty texture, and distinctive taste.
Potato chips, French fries, and other fried potato products have the most acrylamide. (The darker the color, the more acrylamide.) Lower levels are found in some presumably healthier foods—namely breakfast cereals, crackers, and bread, which we tend to consume a lot of. Roasted nuts, peanut butter, olives, some dried fruit, and, yes, coffee also contain low levels. By one estimate, nearly 40 percent of calories in the U.S. come from acrylamide-containing foods. Nonfood sources include cigarette smoke and, to a much lesser extent, drinking water.
Putting this brewhaha in perspective
How risky is acrylamide? The U.S. National Toxicology Program and the International Agency for Research on Cancer (part of the World Health Organization) have deemed acrylamide a likely or probable human carcinogen, based on studies of animals fed very high amounts. But studies in people have had mixed results, with some showing no increased risk in those with the highest dietary intakes. According to the National Cancer Institute, “a large number of epidemiologic studies (both case-control and cohort studies) in humans have found no consistent evidence that dietary acrylamide exposure is associated with the risk of any type of cancer.”
The potential health risks of acrylamide for humans are hard to study, largely because its levels vary tremendously within the same types of foods, not only from brand to brand, but even from batch to batch. And since acrylamide is so prevalent in the food supply, there’s not much difference between low-intake and high-intake groups in observational studies.
Because of Prop 65 lawsuits and consumer concerns, the food industry has been devising strategies to reduce acrylamide in order to avoid labeling—for example, by altering cooking times, temperature, and methods and by using ingredients that help block the formation of acrylamide.
Back to coffee. Like many plant-derived foods, coffee naturally contains thousands of chemicals, plus others, like acrylamide, that are formed during roasting. Research suggests that many of these compounds have potential anti-cancer and other beneficial effects, while others may promote cancer and pose additional risks (some may have both good and bad effects). Of course, as the saying goes, “the dose makes the poison,” and the amounts of various compounds (including acrylamide) in even a whole pot of coffee are truly minuscule.
The good news is that observational studies have consistently linked coffee to a host of potential health benefits, sometimes even a reduced risk of certain cancers, such as prostate, colon, and endometrial cancer, as well as reduced mortality rates. The latest Dietary Guidelines for Americans state that moderate coffee intake has potential health benefits.
If you want to minimize your intake of acrylamide, limit or avoid French fries, chips, cookies, pastries, biscuits, and pies, which tend to have the most acrylamide. Don’t roast potatoes or toast bread until they are dark brown. Above all, don’t smoke: You’ll get much more acrylamide from tobacco smoke than from food.
Also see Acrylamide in Food: Chip Tips.