Do Coffee and Tea Reduce Cancer Risk?

Cancer epidemiologists who study diet have long sought to understand the associations between coffee and tea drinking and the risks for a host of cancer types.

With coffee, weak or inconsistent associations have been reported for breast, ovarian, and other cancers, whereas a growing body of research suggests that regular coffee drinking can lower the risk for liver, endometrial, and colorectal cancers. Late last year, an analysis of pooled data from more than a dozen studies showed higher coffee or tea consumption linked to significantly lower risk for multiple types of head and neck cancer.

Though encouraging, the evidence is not enough to result in formal dietary recommendations — at least not yet, said Caroline Um, PhD, of the American Cancer Society in Atlanta, who works with data from the Cancer Prevention Studies (CPS)-II and CPS-III, both long-term, prospective nutrition cohort studies. In 2020, Um published results from the CPS-II cohort showing reduced risk associated with drinking coffee for colorectal cancers, and plans to study coffee and tea further using data from the newer CPS-III cohort.

It’s important to continue studying coffee and tea, Um said, because “a lot more people are starting to drink it at a younger age now,” as industry studies have shown. At the same time, Um said, “we see cancer rates changing with both colorectal cancer and breast cancer, and we’re starting to see more of both in younger adults. Why is this happening? We don’t know. And we don’t know if the risk factors are the same in the younger patients as for older ones. So we want to try and assess everything possible when we’re trying to figure out those types of answers.”

New Insights From Head and Neck Cancer Studies

For the research published in December 2024, Yuan-Chin Amy Lee, PhD, a cancer epidemiologist at Huntsman Cancer Institute at the University of Utah in Salt Lake City, Utah, and her colleagues, looked at both coffee and tea consumption related to different types of head and neck cancers.

By conducting a pooled analysis of 14 studies that included 9500 cases and nearly 16,000 controls, Lee and her colleagues were able to report that heavy drinkers of caffeinated coffee — people drinking four or more cups daily — saw significantly lower risk for head and neck cancer compared with nondrinkers of coffee (odds ratio, 0.83; 95% CI, 0.69-1.00). Breaking down results by cancer type, they found that oropharyngeal, hypopharyngeal, and oral cavity cancer risk was also significantly lowered with daily coffee consumption.

A key strength of Lee’s study was the large number of cases included, which allowed investigators to look separately both cancer types and beverage types. Drinking at least one cup a day of decaffeinated coffee was associated with a reduced risk for oral cavity cancer, the researchers saw.

The findings add evidence to an emerging consensus that caffeine is not necessarily the mediator of cancer risk with coffee and tea, as was once assumed.

In Um’s colorectal cancer study, daily consumption of decaffeinated coffee was seen associated with an 18% reduction in colorectal cancer risk, a stronger association than for caffeinated coffee.

Lee said that other compounds — including some present in both coffee and tea — probably play bigger roles.

“Based on our observations we feel that polyphenols, bioactive compounds found in all different types of caffeinated coffee, decaf coffee and tea, may be protective,” she said. “They have exhibited antioxidative and anticancer properties in cancer cell lines. But further studies will be required to confirm it.”

Teasing Out Hidden Interactions

Inverse associations with cancer risk were seen for both tea and coffee in Lee’s study. But there was one surprise finding: Risk for laryngeal cancer, one type of head and neck cancer, was higher among regular tea drinkers.

Lee said the researchers hypothesized that this may be because theophylline, a bioactive compound in black tea, can lower esophageal sphincter pressure, resulting in acid reflux and raising laryngeal cancer risk. “But we really need to see more data,” she cautioned.

In Um’s study, coffee, and especially decaf coffee, was seen lowering the risk for all the colorectal cancer types studied. Greater daily consumption of caffeinated coffee, however, was associated with a higher risk for rectal cancer.

“It’s possible that we weren’t able to account for all of the other different risk factors that could contribute to that particular cancer. And with these rarer cancers we have smaller numbers of cases,” she said, pointing to Lee’s finding with laryngeal cancer and tea as similarly hard to interpret.

Such incongruent findings speak to the complexity of the interactions between coffee and tea, their metabolites, and the gut microbiota, all of which could be contributing to risk, Um said.

“We don’t yet know enough yet about the different types of bacteria in our colon, and how they may differ along the parts of the colon. So that’s something we want to look into,” she said, noting that the CPS-III cohort study is collecting microbiome samples as well as dietary information.

Other researchers have studied the metabolites, or metabolic products, of coffee and tea, as measured in the urine and blood, and their links to cancer risk. One research group investigated specific coffee metabolites associated with liver cancer, for which the risks are lower with daily consumption.

“I think it’s going to take more of these molecular-type studies to really understand what’s going on,” Um said. Not only must researchers tease out the roles of phytochemicals like polyphenols, which occur in both coffee and tea, but they need to understand how these are metabolized by individual human bodies, with different genetic profiles, and interacting with individual microbiomes in raising or lowering risk for different cancer types.

“Everyone has a very different metabolism, even with coffee,” Lee said.

Capturing Ever-Changing Habits

Coffee and tea drinking habits are “so complex,” said Lee, who is planning further studies to capture a broader swath of global data to analyze for coffee, tea, and head and neck cancer associations. And because cultures prepare these beverages differently, new associations may emerge.

“With the populations in our most recent study, we didn’t know if people were adding milk, sugar, or other additives,” she said. “Or anything about how the drinks were prepared — different methods of roasting, or how hot the beverages were when they were served, which we think is important with some cancers.”

Um said that “even which country the coffee beans are from” could potentially make a difference, but that such details are very hard to capture.

Additionally, “our diets are always changing because all the types of foods and beverages available and being sold is also changing,” Um said. “How do you keep up with all of that? That’s really a major challenge.”

The coffee and tea consumption by participants in the CPS-II study, which began in the 1980s, would likely be very different than those seen in the CPS-III study, which started in 2006 — when the Starbucks era was well underway. The CPS-III study, which uses detailed nutritional surveys, contains different questions related to coffee and tea than the previous cohort study.

More coffee is being consumed now, and with a huge array of additives that could potentially confound cancer epidemiology studies, including by contributing to obesity, Um said.

Um said that while there is some intriguing evidence of beneficial phytochemicals present in both coffee and tea, they should continue to be studied separately — “ideally with epidemiological studies, molecular studies and randomized trials.”

Both researchers agreed that actionable dietary recommendations are probably a long way off for either coffee or tea. “I think like we saw previously with tobacco and alcohol, it will require a panel of experts in the field to review all the evidence in order to make a call,” Lee said. And that evidence is still dripping in.

The experts interviewed for this piece had no disclosures.