Carcinogens in Coffee and Smokeless Tobacco: Truths & Half-Truths

If a health official announced, “The use of coffee, which contains 21 known human carcinogens, is not harmless,” she would be correct... but not entirely so.

A leading expert in carcinogenesis, Bruce Ames, authored a scientific manuscript in 2000 reporting that 21 known carcinogens are found in coffee (abstract here). Roasted coffee contains thousands of chemicals in addition to addictive caffeine. Some of these agents have been shown in laboratory experiments to cause cancer. Professor Ames also reported that humans consume carcinogens every day in foods and beverages that are considered “safe”; the carcinogens are present in such minuscule quantities that they play no significant role in the development of human cancer. He wrote:

“Naturally occurring pesticides that are rodent carcinogens are ubiquitous in fruits, vegetables, herbs, and spices. Cooking foods produces about 2000 milligrams per person per day of burnt material that contains many rodent carcinogens and many mutagens… In a single cup of coffee, the natural chemicals that are known rodent carcinogens are about equal in weight to a year’s worth of synthetic pesticide residues that are rodent carcinogens, even though only 3% of the natural chemicals in roasted coffee have been adequately tested for carcinogenicity.”

Here are some of the cancer-causing agents in coffee: Acetaldehyde, benzaldehyde, benzene, benzofuran, benzo(a)pyrene, caffeic acid, catechol, 1,2,5,6-dibenzanthracene, ethanol, ethylbenzene, formaldehyde, furan, furfural, hydrogen peroxide, hydroquinone, isoprene, limonene, 4-methylcatechol, styrene, toluene, xylene. And there are still about a thousand chemicals that haven’t been tested.

While this is a scary list, health officials are not calling for a ban on coffee. They know that epidemiologic studies show that coffee, while not absolutely harmless, is quite safe to consume.

Let’s get back to that statement at the beginning of this entry. In fact, a Daviess County (Kentucky) health department official was quoted in a news report, saying, “The use of smokeless tobacco, which contains 28 human carcinogens, is not harmless.” She was commenting on Switch and Quit Owensboro, a public health campaign that tells smokers the truth about vastly safer smoke-free cigarette substitutes (here).

The health department official was parroting a commonly used but almost meaningless factoid about smokeless tobacco. It is used by the CDC (here), the National Cancer Institute (here), the American Lung Association (here), and many state agencies (example here ).

The factoid is essentially meaningless because numerous epidemiologic studies have established that cancer risks associated with smokeless tobacco are so low that they are barely measurable.

Coffee contains 21 carcinogens and smokeless tobacco contains 28; both have high levels of an addictive drug (caffeine and nicotine, respectively). Neither coffee nor smokeless tobacco is absolutely safe, but informed public health practitioners know that the health risks with either are minimal. The real risk is in misleading smokers with partial truths.