Coffee and Tea May Lower Cancer Risk: What We Know, What We Don't, and What Remains Unclear

Understanding the Relationship Between Coffee and Cancer

Scientists studying cancer and nutrition are investigating how coffee and tea consumption relate to different cancers.

Studies suggest the relationship between coffee consumption and

• cancers such as breast and ovarian cancer is weak or inconsistent , whereas
• growing research suggests regular coffee consumption may significantly reduce liver, endometrial (uterine) and colorectal cancer risk.
• A large analysis published in 2024 found that coffee and tea consumption reduced head and neck cancer risk significantly .

Evidence Is Growing, but Firm Recommendations Are Premature

Dr. Caroline Um of the American Cancer Society studies long-term observational cohorts examining these drinks' health effects (CPS-II and CPS-III). Her 2020 CPS-II study found reduced colorectal cancer risk with coffee, and further work is planned using CPS-III.

Dr. Um stresses the importance of understanding long-term effects. Industry reports suggest people start drinking coffee and tea younger, while colorectal and breast cancer are rising in young adults. "We do not know why these changes are happening. Are risk factors the same in younger and older patients, or different? We need to consider all possibilities to understand this", she says.

New Findings in Head and Neck Cancer

A study published in December 2024, led by Dr. Yuan-Chin Amy Lee of the University of Utah's Huntsman Cancer Institute, examined effects across different head and neck cancers.

It combined 14 studies with 9500 patients and 16000 controls. People drinking four or more cups of caffeinated coffee daily had a risk of head and neck cancer that was 17% lower than in non-drinkers (OR: 0.83; 95% CI: 0.69-1.00). Risks of oropharyngeal, hypopharyngeal, and oral cavity cancers also decreased with daily coffee.

The large dataset allowed separate analyses of cancer and drink types. At least one daily cup of decaffeinated coffee was also associated with lower oral cavity cancer risk.

Caffeine or Bioactive Compounds?

The findings suggest protective effects are not due to caffeine alone . In Dr. Um's colorectal cancer study, decaffeinated coffee was associated with an 18% reduction, considered a stronger protective effect than caffeinated coffee.

According to Dr. Lee, coffee and tea polyphenols and other bioactive compounds may play a larger role. Polyphenols have antioxidant and anticancer properties and have shown protective effects in laboratory cancer-cell studies. More research is needed to clarify the mechanisms.

Uncovering Hidden Interactions

Dr. Lee's study generally linked coffee and tea with lower risk, but also observed increased laryngeal cancer risk among regular tea drinkers . Researchers suggest black tea's theophylline could underlie this finding by relaxing the muscles of the esophagus and causing acid reflux. In addition, compared with coffee, tea is consumed at higher temperatures . Reflux may increase esophageal and laryngeal cancer risk over time, but more data are needed to confirm the hypothesis.

Similarly, Dr. Um's study found caffeinated coffee associated with increased rectal cancer risk . Researchers suspect incomplete control of other risk factors may explain conflicting results for certain cancers.

These complex findings show how difficult it is to understand the relationship. Interactions between bioactive compounds and the gut microbiota are important for future research. New cohorts such as CPS-III may collect microbiota samples to clarify these links.

Coffee and Tea Habits Keep Changing

Dr. Lee notes that preparation and drinking habits differ between countries, potentially affecting research findings. "For example, do people add milk, sugar, or other ingredients? How are these drinks brewed or prepared? All of these factors may change their effects on cancer risk."

Even coffee bean origin may affect health, but tracking and analyzing such detail is difficult. Habits when CPS-II began in the 1980s may differ substantially from those when CPS-III began in 2006.

Conclusion

Evidence for protective effects of coffee and tea is growing, but their precise health effects and the components responsible remain uncertain. More molecular and clinical research is needed. Firmer evidence is required before definitive dietary recommendations can be made.