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Apparently, some decaffeination processes (the "direct method", for example) use solvents or other chemicals that don't sound very healthy (dichloromethane "is the least toxic of the simple chlorohydrocarbons, but it is not without health risks", for example).

The article on Wikipedia doesn't talk about the effect of those chemicals used for decaffeination and whether they still can be detected in the final product:

https://en.wikipedia.org/wiki/Decaffeination#Health_effects_of_decaffeinated_coffee

Some mentions that decaffeinated coffee might be bad are marked with "citation needed" in "Health effects of coffee" on Wikipedia:

https://en.wikipedia.org/wiki/Health_effects_of_coffee

Some people still assured me that it was definitely bad for my health.

Olivier Bruchez
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  • Well, dippy birds like dicholoromethane ;-) http://en.wikipedia.org/wiki/Drinking_bird – Highly Irregular Feb 20 '12 at 08:49
  • What's so bad about dichloromethane? Its most serious affect is that it is heavier than air and volatile so can exclude air from an enclosed space killing by asphyxiation (like CO2). It has been extensively studied and doesn't have any known long term harmful effects in people. – matt_black Feb 20 '12 at 14:46
  • This is rather complicated. Caffeine-consumption is correlated with some disease and inversely correlated with some others. Other compounds that are in BOTH coffee AND decaffeinated coffee have simialr effects [example](http://care.diabetesjournals.org/content/28/6/1390.short). So, even before you consider whether there are any ADDITIONAL nasties in decaff, you have a messy playing field. (If your alternative to decaff coffee is, say, cola, the story gets even more murky.) – Oddthinking Feb 20 '12 at 15:18
  • @Oddthinking: So I guess I could rephrase my question as: Is decaffeinated coffee worse than regular coffee for your health? – Olivier Bruchez Feb 20 '12 at 15:38

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Someone asked Alice this, on the Columbia University health page.

The the answer is as follows:

In order for coffee to qualify as decaffeinated, it must have at least 97 percent of its caffeine removed. What does that chock up to? An eight-ounce cup of decaf coffee would have no more than 5 or fewer milligrams of caffeine (compared to the range of 40 - 180 mg. typically found in one eight-ounce cup of brewed, dripped, or percolated java).

Today, most processors use safe methods to remove caffeine. A few different techniques are available, and understanding them may help allay your concerns about coffee contaminants. Coffee beans are decaffeinated by softening the beans with water and using a substance to extract the caffeine. Water alone cannot be used because it strips away too much of the flavor. The goal is to extract the caffeine with minimal loss of flavor. Substances used to remove the caffeine may directly or indirectly come in contact with the beans, and so the processes are referred to as direct or indirect decaffeination.

In one process, coffee beans are soaked in water to soften them and dissolve the caffeine. The water containing the caffeine (and the flavor from the beans) is treated with a solvent, heated to remove the solvent and caffeine, and then returned to the beans. The flavors in the water are reabsorbed by the beans, which are then dried. This process is referred to as "indirect decaffeination," because the beans never touch the solvent themselves. The most widely used solvent today is ethyl acetate, a substance found in many fruits. When your coffee label states that the beans are "naturally decaffeinated," it is referring to this process, specifically using ethyl acetate. Although it doesn't sound like a natural process, it can be labeled as such because the solvent occurs in nature. Other solvents have been used, some of which have been shown to be harmful. One, methylene chloride, has been alleged to cause cancer in humans and therefore is not often used. Back in the 1970s, another solvent, trichloroethylene, was found to be carcinogenic and is no longer used.

Another indirect method soaks the beans in water to soften them and remove the caffeine, and then runs the liquid through activated charcoal or carbon filters to decaffeinate it. The flavor containing fluid is then returned to the beans to be dried. This charcoal or carbon process is often called "Swiss water process" (developed by a Swiss company).

Your concern over the safety of decaffeinated coffee probably stems from solvents used in the past. If your coffee is labeled naturally decaffeinated or Swiss water processed, you can be assured that no harmful chemicals are used. If you are uncertain, you can ask or call your coffee processor to learn about the method used.

I think it is safe to say that any decaffeinated coffee purchased in a country that competently regulates food safety is safe to consume

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