Can coffee interfere with antibiotics? New study reveals a possible link

German scientists have discovered that caffeine can interfere with antibiotics like amoxicillin and ciprofloxacin in bacteria, raising questions about how diet may influence drug effectiveness

A new study has raised doubts that drinking coffee may affect the effectiveness of antibiotics in the body. Researchers in Germany found that caffeine, the main stimulant in coffee, can interfere with how certain bacteria respond to antibiotics, potentially diminishing their efficacy.

 

Study overview

 

The research was led by scientists from the Universities of Tübingen and Würzburg in Germany. The team tested 94 different substances, such as antibiotics, medicines, and food ingredients, on the bacterium Escherichia coli (E. coli) to see how they affect certain genes and proteins. These proteins act like tiny gates and pumps in the bacterial surface, controlling what goes in and out. Keeping this system balanced is vital for the bacteria to survive.

 

 

The study titled ‘Systematic screen uncovers regulator contributions to chemical cues in Escherichia coli’, looked at how caffeine affects bacterial genes that control membrane transport - that is, how molecules (including antibiotics) get into and out of the bacterial cell. 

 

How caffeine interferes

 

Harder for antibiotics to enter bacteria - E. coli usually lets antibiotics like amoxicillin and ciprofloxacin in through a protein ‘door’ called OmpF. Caffeine reduces the number of these doors, making it harder for antibiotics to enter the bacteria.

 

Changes in bacterial controls - Caffeine activates a molecule called MicF, which blocks the production of OmpF. This only happens if another regulator, called Rob, is present. Without Rob, caffeine doesn’t have this effect.

 

“Caffeine triggers a cascade of events starting with the gene regulator Rob and culminating in the change of several transport proteins in E. coli, which in turn leads to a reduced uptake of antibiotics such as ciprofloxacin,” explains Ana Rita Brochado, lead researcher behind the study. The researchers describe this phenomenon as an ‘antagonistic interaction’.

 

In lab tests, bacteria exposed to caffeine needed much higher doses of antibiotics to be controlled. For example, amoxicillin had to be about 40 per cent stronger to work well. The same weakening effect was also seen with ciprofloxacin.

 

Limitations of the study

 

• The adverse caffeine effect was seen in E. coli but not in all bacteria, such as Salmonella.
• The study was done on bacteria in the lab, not in people. It has not been confirmed yet if drinking coffee while on antibiotics has the same effect inside the human body.

 

Why the finding matters 

The study, published in the scientific journal PLOS Biology, makes an important contribution to understanding ‘low-level’ antibiotic resistance. This type of resistance is not caused by classic resistance genes but by changes in regulation and environmental adaptation.

 

The research highlights how what we ingest beyond just the medication could affect treatment outcomes. Even commonly consumed compounds like caffeine might alter how antibiotics work.

 

Since many bacteria (beneficial or pathogenic) are exposed to dietary chemicals, these interactions could also influence the gut microbiome.

 

Future research is needed to determine whether such interactions are relevant in humans, what levels of caffeine might matter, and whether other dietary or environmental chemicals have similar effects. 

 

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