What’s the link between coffee and cancer?

Coffee is one of the most frequently consumed beverages in the world and its popularity continues to rise. But a debate has raged for decades over coffee’s relationship with cancer—a disease that has long been the second leading cause of death globally.

In 1991, the WHO added coffee to its list of possible carcinogens. A quarter of a century later, however, the beverage was removed from the list when a bulk of research found no association between coffee and cancer risk, according to an article published by Harvard T.H. Chan School of Public Health. In fact, the body of evidence demonstrated the opposite—that drinking coffee regularly was linked to a decreased chance of certain cancers. But that didn’t put the debate to bed. 

Coffee was put on trial again years later due to concerns over the chemical acrylamide, which is found in coffee beans after they’ve been roasted. Some research has shown that, at high enough levels, this chemical is a carcinogen. As a result, in 2018, a California judge ruled that all coffee products sold in the state required labels that warned consumers about their “potential cancer risk.” 

However, once again, researchers came to coffee’s rescue, as new evidence demonstrated that levels of acrylamide found in coffee are not high enough to have negative impacts on humans. Coffee was removed from the list of products that require cancer warnings in the state of California after a review of more than 1,000 studies published by the WHO’s International Agency for Research on Cancer concluded there’s inadequate evidence that drinking coffee causes cancer, according to Harvard Health.

More recently, studies have found that coffee may be associated with a decreased likelihood of specific cancers. Here’s a review of the latest research.

Coffee’s effect on cancer

The most recent evidence links coffee consumption with lowered risks of liver and endometrial cancers. This was recently supported by a review of 28 meta-analyses, published in BMC Cancer last year. The review found “highly suggestive evidence for an inverse association between coffee intake and risk of liver and endometrial cancer,” though the authors noted that further research is needed for evidence regarding cancer at other sites. Those research gaps are slowly being filled. 

According to a recent study published in the International Journal of Epidemiology, coffee consumption may be linked with a lower risk of renal cell carcinoma. Researchers examined a cohort of over 420,000 participants from the National Institutes of Health-American Association of Retired Persons Diet and Health Study. They identified 2,674 incident cases of renal cell carcinoma and examined the participants’ coffee drinking habits. The researchers found that those who drink 2 or more cups of coffee a day had a 20% lower risk of developing the disease, compared with no coffee consumption, and concluded that

The authors of the review analyzed 16 studies, with 57,000 cases of prostate cancer, and over 1 million participants. The authors concluded that coffee consumption is “significantly associated with a reduced risk of prostate cancer in men,” at a reduction rate of nearly 1% for each cup of coffee consumed per day. For those who drank the most coffee among the cohort, the authors found a 7% reduction in risk for localized prostate cancer.

On the other hand, a study published in the International Journal of Cancer showed that coffee may not have the same effect on lung cancer. The researchers concluded that a higher level of caffeine consumption was associated with an increased risk of lung cancer, although they noted that the findings may be confounded by participants’ smoking habits.

Is coffee protective against cancer?

Coffee may interact with cancer cells from the moment they develop all the way to their death, according to the Harvard School of Public Health article. Coffee contains polyphenols (micronutrients, found in plant-based foods), which studies have shown can slow or prevent cancer growth in animals.

Additionally, coffee appears to reduce inflammation and has been linked to lower levels of estrogen, a hormone that’s associated with some types of cancer. Beyond this, researchers hypothesize that coffee might stimulate the production of bile acids and increase the pace of digestion, which can limit the exposure of carcinogens to colon tissue.

The aforementioned BMJ Open review noted that coffee is a major source of chlorogenic acids, which may help to increase insulin sensitivity and lower blood glucose levels. Coffee consumption may also be linked to increased levels of adiponectin plasma, which could play a role as an endogenous insulin sensitizer. The dietary antioxidants found in coffee are thought to protect cells from damage caused by oxidative stress and inflammation, which may inhibit the growth of certain cancers. 

And the American Cancer Society (ACS) weighs in as well. It’s true that newer studies associate coffee drinking with a decreased risk of some cancers, but in some of the studies the benefit was found in those who drank 4-6 cups per day, the ACS points out.

“Too much caffeine can interfere with sleep, trigger migraines, and cause digestive problems. And if you take your coffee with cream and sugar, the added fat and calories can contribute to weight gain—which increases the risk for many types of cancer,” noted an article on the ACS website. 

The best way to lower cancer risk, the ACS advises, is to avoid smoking, enjoy a healthy diet, and be physically active. 

Bottom line

Overall, the current evidence seems to give us a thumbs-up for drinking a few cups of coffee per day—especially if we don’t load it up with extra fat and calories, and avoid it before bedtime. And, it may well help keep some cancers at bay. 

To learn more about coffee’s effects on other diseases, click here.