These popular drinks have been proven to reduce cancer risk

Every day, many people roll out of bed with little else on their minds besides that first cup of joe, especially physicians working long shifts that require their full concentration. In fact, humans consume more than 2 billion cups of coffee every day, making coffee one of the most consumed beverages in the world. Americans are particularly coffee-obsessed—we drink 400 million cups per day, making the United States the leading consumer of coffee in the world. But, is this rampant consumption of caffeine good for our health?

Mounting evidence suggests that caffeine consumption offers several important health benefits. In addition to its ability to potentially boost metabolic rates, reduce the risk of type 2 diabetes, and ward off dementia, recent studies suggest that caffeine consumption—including coffee and tea—significantly reduces the risk of nonmelanoma skin cancer (NMSC) in a wide range of patients.

Coffee, black tea, and skin cancer

In the recent Singapore Chinese Health Study, researchers investigated the association of coffee, black and green tea, and caffeine consumption with NMSC risk in a cohort of 63,257 Chinese Singaporeans over 5 years. According to their findings, those who drank ≥ 3 cups of coffee per day had lower risks of basal cell and squamous cell carcinomas than those who drank coffee less than weekly. Black tea, which contains roughly the same amount of caffeine per cup as coffee, also brought about benefits. People who drank it daily had reduced risk of NMSC compared with non-drinkers.

Overall, study participants who drank ≥ 400 mg of caffeine daily—the equivalent of about 4 cups of coffee or black tea—saw the greatest chemoprotective effects, according to the study authors. However, green tea, which has about one-third to one-half of the amount of caffeine as a cup of coffee, did not reduce NMSC risk.

This new data complements evidence from a previous epidemiological study performed in Norway, suggesting that caffeine’s ability to reduce the risk of NMSC is likely consistent across different ethnic groups. In the study, which included more than 16,000 individuals, researchers found a strong negative association between coffee consumption and not just NMSC—but kidney cancer, too.

In fact, a 2017 study suggests that skin cancer is just one of the many types of cancer where caffeine consumption—particularly coffee—might mitigate risk. Specifically, researchers found that among more than 80,000 Japanese participants (age 40–79 years at baseline), those who drank coffee more often had a lower risk of dying from cancer of any type. Adjusted risk of cancer mortality was lowest among men and women with coffee consumption of ≥ 5 cups per day. 

Even when adjusting for potential confounders—including age, BMI, history of smoking, and alcohol consumption status—higher levels of coffee consumption reduced all-sites cancer incidence. In addition to caffeine, coffee’s high concentrations of chlorogenic acid—a compound also found in fruits, vegetables, spices, and wine, and is suspected to have beneficial effects on inflammatory diseases—may have been a key factor in these positive results, according to the researchers.

Is it the coffee, the tea, or the caffeine?

As much as the Singapore Chinese Health study clarifies the associations of coffee and tea consumption with the risk of NMSC, it raises further questions about the specific drivers of these associations. The study authors ultimately claimed that the reduced risk of NMSC was attributable to “a high intake of caffeine,” rather than a high intake of coffee or tea in particular, despite the fact that the association was not seen in soda or cocoa drinkers. Moreover, the evidence revealed differences in risk reduction between coffee and tea: Coffee was associated with reduced risk of squamous cell carcinoma and basal cell carcinoma, while black tea consumption was only associated with a reduction in risk of squamous cell carcinoma.

“A major challenge in the epidemiological study of coffee and health outcomes has been the relationship between coffee and caffeine,” wrote senior author Naiem T. Issa, MD, PhD, Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, and colleagues in a response to the study.

Because of the number of studies showing an association between coffee consumption and many different kinds of disease, Dr. Issa and coauthors advocated for more randomized prospective trials to look further into the details of these associations. They noted that one study conducted in Finland, for example—which carefully collected serum samples from 47 habitual coffee drinkers who drank consistent quantities of the same type of coffee—uncovered new pathways influenced by coffee consumption.

What about other caffeine sources?

People in many nations are fond of their coffee and tea. But, residents of the United States are perhaps better known for their love-hate relationship with soft drinks, which—despite often high levels of additives and sugar—typically contain about one-third to one-half the caffeine content of coffee. Other sources of caffeine, like caffeine pills, chocolate, and cocoa drinks, might also come into question. Do these alternative sources of caffeine provide the same chemoprotective benefits as coffee and tea?

Not according to the evidence, said lead author of the Singapore Chinese Health Study, Oh Choon Chiat, MD, Department of Dermatology, Singapore General Hospital, Singapore.

“Coffee and tea (black and green) accounted for 84% and 12% of total dietary caffeine intake in our cohort, respectively. The remaining contribution (4%) came from other caffeinated food sources such as soda (0.7%), cocoa drinks, and chocolate-related food items,” Dr. Choon Chiat told MDLinx. “However, only coffee and black tea showed reduction in risk of developing [NMSCs].”

Evidence from other studies supports Dr. Choon Chiat’s claim and points to sugary soda as a cause of cancer, rather than a cancer-reducing agent. In a large prospective study of the link between sugary drink intake and cancer risk—which included more than 100,000 participants from the French NutriNet-Santé cohort (2009–2017)—the consumption of sugary drinks like soda and fruit juice was significantly associated with the risk of overall cancer. However, that risk was not seen in participants who consumed artificially sweetened beverages like diet soda.

What we still don’t know

They say that too much of anything can be a bad thing—and caffeine is no exception. For all of caffeine’s many positives, there’s still so little that researchers know about the world’s favorite addictive drug. And this lack of knowledge is what makes it so difficult to determine caffeine’s safety and potential therapeutic value. 

“Although we await results of randomized controlled trials, we must not ignore the other bioactive molecules that may be present in coffee. More needs to be learned, and the potential for therapeutic gain exists; therefore, we suggest that dermatologists and scientists think beyond caffeine and consider a role for the other molecules in coffee,” Dr. Issa and colleagues concluded.

While academics sort out details that remain to be discovered, physicians can feel secure in enjoying their daily cup(s) of coffee or tea—but should continue to steer clear of sugary drinks.