How does coffee fight cancer?

You may very well be drinking coffee as you read this. Are the chemical compounds in your coffee working at this very moment to fend off cancer in your throat, your liver, or your colon? According to several studies, drinking coffee does, indeed, reduce the risk of these and other cancer types. But how does coffee do it? Is it the caffeine, the roasting process, or something in the coffee bean itself?

And if we can find out how coffee does it, can we create a drug from it to combat cancer directly?

Coffee vs cancer

In numerous studies, researchers have demonstrated coffee’s anticarcinogenic and anti-inflammatory properties. (Although some studies have not found associations between coffee drinking and reduced risk of cancer.) In one meta-analysis, researchers compared people with low coffee intake vs those with high coffee intake. The researchers found that coffee reduced liver cancer by 54%, oral and pharyngeal cancer by 31%, endometrial cancer by 27%, colon cancer by 13%, prostate cancer by 11%, and melanoma by 11%.

These same researchers found a dose-response relationship to coffee drinking and certain types of cancer. Specifically, two extra cups of coffee per day reduced the risk of liver cancer by 27%, endometrial cancer by 12%, and prostate cancer by 3%.

On the other hand, coffee intake seemed to increase the risk of lung cancer by 118%. However, investigators noted that drinking coffee frequently goes hand-in-hand with cigarette smoking, which likely accounts for the increased risk of lung cancer in coffee drinkers.

Finding common grounds

Coffee is one of the most popular drinks in the world. More Americans than ever—63% of adults—now drink coffee daily.

The dark brew also contains many substances that affect the human body, including caffeine, caffeic acid, chlorogenic acid, and diterpenes such as cafestol and kahweol.

• Caffeine. Coffee may reduce the risk of colorectal cancer thanks to caffeine, which can rush carcinogens through the digestive tract, thereby reducing the gut's exposure to them. Caffeine may also possess antioxidant properties, and may limit the growth and migration of colon cancer cells. In cell studies, caffeine influenced cell signaling, which suppressed cell growth and boosted apoptosis of colorectal cancer cells.

However, researchers studying decaffeinated coffee found that it, too, reduced colon cancer risk, which shows that caffeine isn’t the only active compound in coffee.

• Caffeic acid. Researchers have found that caffeic acid possesses anti-inflammatory, anticarcinogenic, and enzyme-inhibiting properties. As with other coffee polyphenols, caffeic acid demonstrates anti-tumor activity.

Caffeic acid is a metabolite of another coffee compound, chlorogenic acid.

• Chlorogenic acid. Coffee is the primary source of chlorogenic acid in the human diet, and the level of chlorogenic acid increases in the body depending on how much coffee you drink. In cell studies, researchers showed that chlorogenic acid appeared to overproduce reactive oxygen species in human colon cancer cells, which conferred an anti-tumor effect.

• Cafestol and kahweol. These compounds have both anticarcinogenic and chemoprotective properties. Acting as antioxidants, kahweol and cafestol protect against oxidative stress and DNA damage. They are believed to block proteins that activate carcinogens, thereby inhibiting cell growth and proliferation. But they also stimulate enzymes that inactivate carcinogens and increase apoptosis of cancer cells.

Note that these are just a few of the better-known compounds in coffee. There are others that aren’t as well-investigated, and more that haven’t yet been identified.

Moreover, the amount of bioactive compounds in coffee depends on many factors. For example, the concentration of caffeine in coffee differs by the method of brewing (drip, boiled, pour over, etc), the type of coffee (regular coffee or espresso), and how dark the beans are roasted—not to mention the type of bean itself (ie, robusta beans have twice the caffeine of Arabica beans).

Also, the size of the coffee grounds and the number of boiling-water pours influence the concentration of chlorogenic acid, while using a filter (or not) as well as the filter’s material affect the concentration of kahweol.

All in all, coffee is like a cancer fighter in a cup.