News Release

Half of all commonly used drugs profoundly affecting the gut microbiome, warn experts

Peer-Reviewed Publication

Spink Health

UEG Week Barcelona 2019

image: The drug categories found to have the biggest impact on the microbiome include, proton pump inhibitors (PPIs), metformin, antibiotics and laxatives. view more 

Credit: UEG

(Barcelona, October 23, 2019) A new study presented at UEG Week 2019 has found that 18 commonly used drug categories extensively affect the taxonomic structure and metabolic potential of the gut microbiome. Eight different categories of drugs were also found to increase antimicrobial resistance mechanisms in the study participants.

Researchers at the University Medical Center Groningen and the Maastricht University Medical Center looked at 41 commonly used drug categories and assessed 1883 faecal samples from a population-based cohort, patients with IBD and patients with IBS intermixed with healthy controls. The researchers compared the taxonomic and metabolic functions profiles of drug users to non-drug users, looking at the effect of single medication use and then combined medication use. The changes observed could increase the risk of intestinal infections, obesity and other serious conditions and disorders linked to the gut microbiome.

Gut microbiota is the microbe population living in the intestine. It contains tens of trillions of microorganisms, including at least 1000 different species of known bacteria. The human gut's microbiota population is influenced by a number of different factors, including medication. The microbiome has received increasing attention over the last 15 years with numerous studies reporting changes in the gut microbiota during not only obesity, diabetes, and liver diseases but also cancer and neurodegenerative diseases.

The drug categories found to have the biggest impact on the microbiome include:

  • Proton pump inhibitors (PPIs) - used to treat dyspepsia which affects between 11% and 24% of the European population. PPIs are also used to treat peptic ulcer, H. Pylori eradication, Gastro reflux and Barrett's oesophagus.

  • Metformin - used as a treatment for Type 2 diabetes, affecting 10% of European adults

  • Antibiotics - used to treat bacterial infections, taken by 34% of the European population each year

  • Laxatives - used to treat and prevent constipation, affecting 17% of European adults

The gut microbiota of PPI users showed increased abundance of upper gastrointestinal tract bacteria and increased fatty acid production, while metformin users had higher levels of the potentially harmful bacteria Escherichia coli (E. coli).

The researchers also found that an additional seven drug categories were associated with significant changes in bacterial populations in the gut. The use of certain antidepressants (called SSRIs) by those with IBS was associated with an abundance of the potentially harmful bacteria species Eubacterium ramulus. The use of oral steroids was associated with high levels of methanogenic bacteria which has been associated with obesity and an increase in BMI.

Commenting, lead-researcher Arnau Vich Vila said: "We already know that the efficiency and the toxicity of certain drugs are influenced by the bacterial composition of the gastrointestinal tract and that the gut microbiota has been related to multiple health conditions; therefore, it is crucial to understand which are the consequences of medication use in the gut microbiome. Our work highlights the importance of considering the role of the gut microbiota when designing treatments and also points to new hypotheses that could explain certain side-effects associated with medication use."


Notes to Editors

For further information, or to arrange an interview with Arnau Vich Vila, please contact Luke Paskins on +44 (0)1444 811099 or

We kindly ask that a reference to UEG Week 2019 is included when communicating any information within this press release.

About Arnau Vich Vila

Arnau Vich Vila is a computational biologist specialized in the study of human gut microbiota. He is currently finalizing his PhD under the supervision of professor Rinse K. Weersma at the department of Gastroenterology and Hepatology of the University Medical Center of Groningen. His research focuses on the role of the gut microbiota in gastrointestinal diseases and the impact of environmental factors on the gut ecosystem. In the recent years he has published studies describing the microbial signatures in patients with inflammatory bowel disease and irritable bowel syndrome and identifying the effect of proton-pump inhibitors on the gut microbiota.

About UEG Week

UEG Week is the largest and most prestigious gastroenterology meeting in Europe and has developed into a global congress. It attracts over 14,000 participants each year, from more than 120 countries, and numbers are steadily rising. UEG Week provides a forum for basic and clinical scientists from across the globe to present their latest research in digestive and liver diseases, and also features a two-day postgraduate course that brings together top lecturers in their fields for a weekend of interactive learning.

About UEG

UEG, or United European Gastroenterology, is a professional non-profit organisation combining all the leading European medical specialist and national societies focusing on digestive health. Together, its member societies represent over 30,000 specialists, working across medicine, surgery, paediatrics, gastrointestinal oncology and endoscopy. This makes UEG the most comprehensive organisation of its kind in the world, and a unique platform for collaboration and the exchange of knowledge.

To advance the standards of gastroenterological care and knowledge across the world and to reduce the burden of digestive diseases, UEG offers numerous activities and initiatives, including:

  • UEG Week, the biggest congress of its kind in Europe, and one of the two largest in the world

  • UEG Education, the universal source of knowledge in gastroenterology, providing online and classroom courses, a huge online library and delivering the latest GI news, fostering debate and discussion

  • Activity Grants, promoting and funding educational projects in the field of digestive health to advance and harmonise the training and continuing education of professionals

  • UEG Journal, covering translational and clinical studies from all areas of gastroenterology

  • Public Affairs, promoting research, prevention, early diagnosis and treatment of digestive diseases, and helping develop an effective health policy for Europe

  • Quality of Care, European-based and English clinical practice guidelines, clinical standards, consensus, position papers and standard protocols in the field of digestive health, are available in the repository.

Find out more about UEG's work by visiting or contact:

Luke Paskins on +44 (0)1444 811099 or


1. Vich Vila, A. et al., 2019. Impact of 41 commonly used drugs on the composition, metabolic function and resistome of the gut microbiome. Presented at UEG Week Barcelona October XX, 2019.

2. Cani PD., Human gut microbiome: hopes, threats and promises Gut 2018;67:1716-1725.

3. World Journal of Gastroenterology. 2006. Epidemiology of functional dyspepsia: A global perspective. [ONLINE] Available at:

4. WHO Europe (2019) Diabetes: Data and statistics, Available at: European Commission. 2016.

5. Special Eurobarometer 445: Antimicrobial Resistance. European Commission; Brussels, Belgium.

6. Peppas, George, et al., 2008. "Epidemiology of constipation in Europe and Oceania: a systematic review." BMC gastroenterology 8.1: 5.

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