In the early 1900s, according to coffee lore, German coffee merchant Ludwig Roselius discovered decaf by accident after a shipment of coffee beans was soaked in seawater during transit, naturally extracting some of the caffeine.

A few years later, Roselius patented the first commercially successful means of decaffeinating coffee. But instead of just salt water, his method also used a more potent chemical solvent called benzene to finish the job.

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We now know that when inhaled, even in small amounts, benzene can cause drowsiness, dizziness, and headaches, as well as eye, skin, and respiratory tract irritation. Over the long term and in high doses, benzene has been linked to cancer, blood disorders, and fetal development issues in pregnant women.

It’s no wonder the new type of brew—which later relied on other similarly toxic solvents—got a bad rap.

Today, coffee manufacturers have switched to safer decaffeination methods, though many still use potent chemicals to strip away caffeine. Meanwhile, researchers have wondered whether any of coffee’s healthful compounds are lost along with the caffeine.

So is decaf healthy? We talked to experts including William D. Ristenpart, Ph.D., a professor of chemical engineering at the University of California, Davis, and director of the UC Davis Coffee Center, to figure out what we really know.

How Decaffeination Works

There are three key methods for removing caffeine from regular coffee beans: The most common uses a chemical solvent, another uses liquid carbon dioxide (CO2), and the last simply uses water.

All take green, unroasted coffee beans, soak or steam them until the caffeine is dissolved or their pores are opened, and then extract the caffeine.

While the CO2 and water methods are considered chemical-free, the solvent method relies on synthetic chemicals such as ethyl acetate (naturally found in some fruits) and methylene chloride (commonly used in industrial applications such as in adhesives, paints, and pharmaceuticals).

The Swiss Water Process tends to produce the most flavorful coffee, Ristenpart says, because it’s good at removing caffeine and without stripping other flavorful compounds from the beans. But it’s also more expensive and difficult to produce at scale. For this reason, Ristenpart says, you’ll typically find it used on higher-end coffees, such as Blue Bottle. (See our coffee ratings for the best beans.)

None of these methods scrubs the bean of caffeine completely. While the Food and Drug Administration requires that at least 97 percent of caffeine be removed, some decaffeinated coffees can still contain between 3 and 12 mg of caffeine per cup. 

Does Decaffeinated Coffee Have Risks?

While experts agree that the Swiss Water Process and liquid carbon dioxide don’t introduce any health risks, methylene chloride is controversial in some coffee circles.

When inhaled in small doses it can cause coughing, wheezing, and shortness of breath. At higher doses, it can cause headache, confusion, nausea, vomiting, dizziness, and fatigue, and has been found to cause liver and lung cancer in animals.

In 1999, however, the FDA concluded that the trace amounts you get in decaf coffee are too minuscule to affect your health. The agency strictly limits its presence to no more than 10 parts per million, or 0.001 percent, of the final product.

Coffee producers will sometimes say that beans decaffeinated with ethyl acetate are “naturally decaffeinated” because the compound is naturally found in some produce. But as with methylene chloride, the ethyl acetate is typically produced synthetically and carries some risks at high doses.

The bottom line, Ristenpart says, is that the solvents used in the decaffeination process today are much safer than they used to be, and they are generally found on beans only in trace amounts. 

Which Decaf Should You Choose?

Experts say you shouldn’t be concerned about the chemicals used in the decaffeination process. But if you are looking to minimize your exposure, you might want to know which decaffeination method was used on a particular bag.

This may be more challenging to find out than you think, Ristenpart says, because there are no specific labeling rules that require disclosing exactly how coffee was decaffeinated.

“If consumers want to be sure that synthetic solvents weren’t used to decaffeinate, they should look for the organic seal,” says Charlotte Vallaeys, Consumer Reports’ senior policy analyst and food-label expert. That seal prohibits not only pesticides, but chemical solvents during processing, too.

If your beans are not organic, ask your supplier which method was used, either in person if you’re buying local or over the phone. If it used the solvent process, there are probably trace amounts of chemical residue on the beans. 

Is Decaffeinated Coffee as Healthy as Regular?

Because decaffeination itself is generally considered safe, the bigger question is whether decaf has the same health benefits as regular coffee.

This is a tough question to answer, says Angela M. Zivkovic, Ph.D., an assistant professor in the department of nutrition at the University of California, Davis, and we don’t yet have a firm answer.

A 2014 meta-analysis published in the journal Diabetes Care and led by researchers from Harvard found that those who drank six cups of coffee per day had a 33 percent lower risk of developing type 2 diabetes than those who drank no coffee. The reduced risk was seen for both decaf and regular coffee.

Another study published in the Annals of Internal Medicine in 2008 found that coffee-drinking in general was not associated with a higher risk of dying from any cause, and even further, those who drank decaf were slightly less likely than those who drank regular to die from any cause.

Zivkovic says, however, that we should interpret such results with caution because “it is very possible and likely that people who choose decaf are also making other ‘healthy’ lifestyle choices.”  

In short, though some studies suggest that decaffeinated coffee is linked to health benefits, more research is needed.

Is Decaffeinated Coffee for You?

We still don’t know whether it’s the caffeine, or one of the thousands of other biologically active compounds and antioxidants (which decaf seems to have, too, albeit at slightly lower levels), that may be responsible for coffee’s many health perks.

What’s really clear, however, is that for people who experience insomnia, irritability, headaches, nausea, anxiety, jitters, and increased blood pressure after drinking too much caffeine, switching to decaf may be a healthy option, says Edward Giovannucci, M.D., Ph.D., a researcher and professor of nutrition and epidemiology at Harvard’s T.H. Chan School of Public Health.