Plain English Summary
Background and study aims
Irritable bowel syndrome (IBS) is a disease that can cause bloating, diarrhoea, constipation and intestinal discomfort. It can also lead to dysbiosis, which is where there is a disturbance or imbalance in the microbes that live in the gut (gut microbiota), along with inflammation of the intestines. There is not yet an effective way to treat IBS.
Essential oils, which are natural oils that come from plants, are considered to be antibacterial and anti-inflammatory, and are known to have an effect on gut microbiota. Geraniol is a compound that comes from essential oils from plants such as lemongrass and rose, and has been shown to have strong anti-inflammatory properties. Additionally, geraniol has been shown to be effective against colitis (a symptom of IBD) and dysbiosis in studies on mice.
As geraniol is safe for humans, we aimed to determine whether geraniol was effective at reducing inflammation and dysbiosis in patients with IBD.
Who can participate?
Patients with IBS aged 18-65, weighing between 48 and 104 kg with a BMI of less than 27.
What does the study involve?
Participants will be asked to take capsules of geraniol orally daily for 4 weeks (geraniol dose depends on body weight) and will be asked to provide fecal samples before treatment, after 4 weeks of treatment and 4 weeks after treatment has ended.
What are the possible benefits and risks of participating?
The possible benefit to participants of taking part is that previous studies have shown that similar treatments that affect gut microbiota lead to improvement of IBD symptoms such as bloating and diarrhoea; therefore, this may also be the case for geraniol treatment. There are no known risks to participants of taking part.
Where is the study run from?
1. Inflammatory Bowel Disease Unit, S. Orsola-Malpighi Hospital, Bologna, Italy (lead centre)
2. Spedali Civili di Brescia, Brescia, Italy (satellite centre)
When is the study starting and how long is it expected to run for?
January 2015 to December 2017
Who is funding the study?
1. University of Bologna (Italy)
2. Xeda International SA (France)
Who is the main contact?
Professor Enzo Spisni
Prof Enzo Spisni
Via Selmi 3
Effect of dietary geraniol on intestinal dysbiosis in irritable bowel syndrome patients
Geraniol could be a food supplement with anti-inflammatory and anti-dysbiotic activity in irritable bowel syndrome (IBS) patients.
Ethics Committee of the AOU Policlinico S. Orsola-Malpighi, 29/10/2013, CE code 100/2013/U/Sper
Ethics Committee of the ASST Spedali Civili di Brescia, 03/06/2015, CE code NP2047
Interventional open label non-randomised multi-centre pilot study
Primary study design
Secondary study design
Non randomised study
Patient information sheet
See additional files
Irritable bowel syndrome (IBS)
Participants underwent geraniol treatment for a period of 4 weeks and was taken daily at a maximum dose of 8 mg/Kg/day. Geraniol was provided in capsules containing 150 mg geraniol and 160 mg soy lecithin. The number of capsules given was calculated depending on the body weight of partcipants.
1. Participants weighing 48-59 kg were given a dose of 3 capsules per day
2. Participants weighing 60-74 kg were given a dose of 4 capsules per day
3. Participants weighing 75-89 kg were given a dose of 5 capsules per day
4. Participants weighing 90-104 kg were given a dose of 6 capsules per day.
After taking geraniol daily for 4 weeks, there was 4 weeks of follow up - a 'wash out' period where geraniol was not taken.
Participants were asked to provide fecal samples before treatment, after 4 weeks of treatment and 4 weeks after treatment was complete.
Primary outcome measure
Changes in fecal microbiota composition after 4 weeks of geraniol administration was measured through phylogenetic DNA array analysis of fecal samples before starting geraniol treatment (visit 1), after 4 weeks of treatment (visit 2) and 4 weeks after treatment finished (visit 3, after 4 weeks of wash out).
Secondary outcome measures
1. Fecal microbial composition in patients with IBS was measured using phylogenetic DNA array analysis of fecal samples before starting geraniol treatment (visit 1).
2. Changes in the microbiota-immune system axis was measured through Luminex analysis of plasma for the levels of cytokines and chemokines involved in the T helper 17 pathway (IL-1β, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, IFN-γ, sCD40L, TNF-α). This was measured before starting geraniol treatment (visit 1), after 4 weeks of treatment (visit 2) and 4 weeks after treatment finished (visit 3).
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1) Signature of informed consent
2) Irritable bowel syndrome, meeting the Roma III criteria for diagnosis of IBS
3) Body weight between 46 kg and 100 kg, with BMI less than 27
4) Aged 18-65 years
Target number of participants
Participant exclusion criteria
1. Taken steroid anti-inflammatory drugs, antibiotics or supplements and/or functional foods containing probiotics or prebiotics in the months prior to enrolment
2. Pregnancy, suspected pregnancy or breastfeeding
3. Diagnosed with IBD
4. Coeliac disease
5. Severe systemic disease
6. Lactose intolerant
7. Known food allergies
8. Known or suspected hypersensitivity to geraniol or soy
9. Serious concomitant diseases that contraindicate participation in the study (in the opinion of the investigator)
10. Use of experimental drugs in the 2 months prior to enrolment
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
S. Orsola Hospital, Pad. 5, Via Massarenti 49
Trial participating centre
Spedali Civili di Brescia, Piazzale Spedali Civili, 1
Università di Bologna
University of Bologna, UNIBO
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
We intend to publish in BMC Complementary and Alternative Medicine.
IPD sharing statement:
Data was collected in pseudonymous form and explicit consent to provide raw data to third parties not involved in the clinical trial was not given by the patients. The explicit consent was given only to publish data in an aggregate form.
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)
The results show that orally administered Ge-OH is a powerful antimicrobial agent of the intestinal microbial ecosystem, capable of leading to increased relative abundances of Collinsella and especially Faecalibacterium, a well-known health-promoting butyrate producer consistently found to be decreased in IBS patients. Moreover, Ge-OH strongly improved the clinical symptoms of colitis by significantly reducing the score recorded by the Visual Analogue Scale for Irritable Bowel Syndrome (VAS-IBS) questionnaire. Clinical improvement was associated with a significant reduction in the circulating MIP-1ba chemokine found to be increased in several IBS patients.
- ISRCTN47041881_PIS.docx Uploaded 02/04/2019