Condition category
Nutritional, Metabolic, Endocrine
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
Metabolic syndrome is a term used to describe a combination of factors which increase a person’s risk of heart disease and other health problems, such as diabetes and stroke. Many of these factors are linked with obesity, such as high blood pressure, cholesterol and body fat. Recent research has shown that there may be a link between the composition of different bacteria that live in the gut (gut microbiota) and the biological processes of disease. In a previous study, it was found that a Mediterranean diet, supplemented with nuts, led to a major reduction in disease risk factors. The aim of this study is to look at two different diets to find out what effect they have on the composition of bacteria in the gut and on metabolic risk factors.

Who can participate?
Men and women aged 30-65 who have three or more signs of metabolic syndrome

What does the study involve?
Participants are randomly allocated to consume two diets in a random order. Each of the diets lasts for eight weeks, and there is a four week period of consuming a normal diet in between them, to ensure the results of the different diets don’t influence each other. The first diet involves eating 50g of nuts every day in addition to regular diet. The second diet involves eating a Mediterranean diet, which involves high consumption of vegetables and olive oil and moderate consumption of protein. Before and after each dietary period, participants provide stool and blood samples which are then examined to assess the composition of bacteria living in the gut and to see if there has been any change to metabolic syndrome risk factors.

What are the possible benefits and risks of participating?
Participants may benefit from taking part due to the well founded benefits of consuming nuts and following a Mediterranean diet. There is a small risk of pain or bruising when blood samples are collected.

Where is the study run from?
1. Rovira i Virgili University (Spain)
2. Hospital Universitari Sant Joan (Spain)

When is the study starting and how long is it expected to run for?
January 2017 to December 2019

Who is funding the study?
Instituto de Salud Carlos III (Spain)

Who is the main contact?
Dr Mònica Bulló Bonet

Trial website

Contact information



Primary contact

Dr Mònica Bulló Bonet


Contact details

Unitat de Nutrició Humana
Universitat Rovira i Virgili (URV)
C/Sant Llorenç
+34 977 75 93 13

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Effect of a diet on healthy food or a Mediterranean diet on change in the composition and function of faecal microbiota and its relationship with the metabolic improvement



Study hypothesis

The consumption of certain foods typical of the Mediterranean diet in the context of a non-Mediterranean diet will modify the composition and functionality of the intestinal microbiota towards a healthier profile.

Ethics approval

Ethics Committee (Hospital Universitari Sant Joan; Reus), 26/01/2017, Ref. CEIm: 04/2017

Study design

Randomised cross over trial

Primary study design


Secondary study design

Randomised cross over trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Obesity and metabolic syndrome


Participants are randomised to consume two dietary interventions in a random order. Each intervention period lasts for a total of eight weeks, with a four week wash out period between them.

Diet one: Participants consume their regular diet (RD) with the addition of 50g of nuts/day.
Diet two: Participants consume the Mediterranean diet. This consists of high consumption of vegetables and olive oil and moderate consumption of protein.

Participants will be followed up before and after each intervention period. Classic metabolic risk markers will be analyzed (glucose, lipid profile) as well as inflammation, oxidation and endothelial function markers by routine methods. The taxonomic composition in faeces will be determined as well as a quantitative metagenomic analysis in one sub-group. For the metabolomic analysis in plasma and faeces samples it will be use different analytic platforms according to the sample.

Intervention type



Drug names

Primary outcome measure

Metabolic risk markers are assessed by measuring glucose and lipid profile, inflammation, oxidation, and endothelial function markers by routine methods, ELISA and Luminex platform at baseline and 8 weeks in each intervention period.

Secondary outcome measures

Faecal microbiota is assessed through measuring the taxonomic composition in faeces (16S RNA) and quantitative metagenomic analysis at baseline and 8 weeks in each intervention period.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Men and women
2. 30-60 years old - updated 17/10/2018: 30-65 years old
3. BMI≥25 and <35
4. ≥3 Metabolic Syndrome criteria:
4.1. Hypertension or hypertension treatment
4.2. Altered glycemia (≥100mg/dl)
4.3. HDL cholesterol (men<40mg/dl or women <50mg/dl)
4.4. Altered triglycerides (≥150mg/dl)
4.5. Abnormal waist circumference (men ≥ 102cm or women ≥ 88)

Participant type


Age group




Target number of participants

50 individuals

Participant exclusion criteria

1. BMI<25kg/m2 or BMI≥35
2. Type 2 diabetes
3. Secondary obesity or related pahologies
4. Non-controlled hypertension (Systolic arterial pressure (SAP)>159mmHg; Diastolic arterial pressure (DAP)>99mmHg)
5. LDL cholesterol >160mg/dl
6. Tryglicerides >400mg/dl
7. Mediterranean adscription punctuation ≥7 (PREDIMED trial)
8. Frequent nuts consumption (≥90g/week)
9. Frequent legumes consumption (≥120g/week)
10. Different chronic diseases (inflammatory, infectious, chronic obstructive pulmonary, neoplasias, endocrine, or hematological diseases)
11. Leucocytosis (leucocytes >11x10E9)
12.Pharmacological treatment (anti-inflammatory, corticoids, hormones or antibiotics)
13. Changes of diabetes, hypertension of lipidic profile medication (last 3 months).
14. Body weight loss (>5kg in the last 3 months).
15. Lost weight medication changes (last 3 months).
16. Breeding or pregnancy.
17. Diseases history (hepatic cirrhosis, intestinal inflammatory, intestinal resection).
18. Nuts or legumes allergy.
19. Probiotics, prebiotics or laxatives consumption

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Rovira i Virgili University (URV)
Human Nutrition Unit (Unitat de Nutrició Humana) C/Sant Llorenç, 21

Trial participating centre

Hospital Universitari Sant Joan
Av/del Dr. Josep Laporte, 2

Sponsor information


Instituto de Salud Carlos III

Sponsor details

St/Sinesio Delgado
28029 Madrid
+34 91 822 20 00

Sponsor type




Funder type


Funder name

Instituto de Salud Carlos III

Alternative name(s)

Institute of Health Carlos III, Carlos III Health Institute, ISCIII

Funding Body Type

government organisation

Funding Body Subtype

National government



Results and Publications

Publication and dissemination plan

Planned publication in a high-impact peer reviewed journal.

IPD Sharing plan;
The datasets generated during and/or analysed during the current study are/will be available upon request from Dr Mònica Bulló Bonet (

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

17/10/2018: The target number of participants was changed from 30 to 50, and the inclusion criteria were updated.