Drinking Coffee Might Weaken the Effect of Antibiotics

A new study suggests that drinking coffee and other caffeine-containing foods may weaken the effectiveness of certain antibiotics. The research, led by Professor Ana Rita Brochado at the Universities of Tübingen and Würzburg, highlights how everyday dietary habits can subtly affect bacterial resistance to drugs.

The team focused on Escherichia coli (E. coli), a bacterium capable of causing serious infections. Their findings reveal that E. coli responds to chemical signals in its environment through complex regulatory processes. These responses can determine how the bacterium absorbs and reacts to antimicrobial treatments.

Researchers say this response is linked to bacterial import and export systems, known as porins and efflux pumps, which manage how molecules, including drugs, cross the cell membrane. These systems form a selective barrier, crucial for survival, but also a key factor in resistance to antibiotics. Mutations or regulatory changes in these proteins have long been associated with clinical drug resistance.

Screening 94 different substances

The researchers systematically tested 94 substances, including antibiotics, prescription medications, and food ingredients, to see how they influenced key gene regulators and transport proteins in E. coli.

Transport proteins function as pores and pumps within the bacterial membrane, controlling what enters and exits the cell. Maintaining balance in these processes is crucial for bacterial survival.

“Our data show that several substances can subtly but systematically influence gene regulation in bacteria,” said Christoph Binsfeld, a Ph.D. student and first author of the study published in PLOS Biology. He added that even compounds with no direct antimicrobial effect, such as caffeinated drinks, can influence how bacteria respond to antibiotics.

How caffeine triggers changes

According to Brochado, caffeine initiates a chain of events beginning with the gene regulator Rob. This activation leads to changes in multiple transport proteins, ultimately reducing the amount of certain antibiotics, such as ciprofloxacin, that enter the bacterial cell. The reduced uptake weakens the antibiotic’s overall effect, a reaction researchers describe as an “antagonistic interaction.”

Coffee Can Interfere With Common Medications, Over-the-counter and Prescription. #coffee #caffeine #deongestants #asthma #adhd #thyroid #depression #anxiety #pain #osteoporosis pic.twitter.com/0wFjSoOvFf

— Dr. Howard Smith Reports (@DrHSmithReports) July 21, 2025

The phenomenon was not observed in Salmonella enterica, a bacterium closely related to E. coli. This difference, the team noted, likely stems from variations in transport pathways or their role in antibiotic absorption.

Implications for Future Treatments

President Prof. Dr. Dr. h.c. (Dōshisha) Karla Pollmann said the findings highlight the value of basic scientific research. “Such fundamental research into the effect of substances consumed daily underscores the vital role of science in understanding and resolving real-world problems,” she said.

The study provides insight into what scientists call “low-level” antibiotic resistance—a type not caused by traditional resistance genes but by regulatory and environmental adaptations. These results could guide future therapeutic approaches, including decisions about diet and medication combinations during antibiotic treatment.