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Protocol Details

Mediterranean-like Unprocessed (CLEAN-MED) Diet Intervention Study of the Gut Microbiome of Healthy Adults

This study is currently recruiting participants.

Summary | Eligibility | Citations | Contacts




Sponsoring Institute

National Institutes of Health Clinical Center (CC)

Recruitment Detail

Type: Participants currently recruited/enrolled
Gender: Male & Female
Min Age: 18 Years
Max Age: 60 Years

Referral Letter Required


Population Exclusion(s)

Pregnant Women;
Non-English Speaking;


Immune System;
Gastrointestinal Tract

Recruitment Keyword(s)



Diet Therapy

Investigational Drug(s)


Investigational Device(s)



Other: Western Diet

Supporting Site

NIH Clinical Center


Trillions of tiny organisms-including bacteria, fungi, and viruses-live inside our intestines. These microorganisms break down nutrients in our food, aid our immunity, and help keep us healthy. The population balances among these organisms can vary in different people due to factors including genetics, lifestyle, and diet. More studies are needed to understand how dietary habits affect our intestinal microorganisms.


To see how switching from a traditional Western diet (low in fiber, high in saturated fat) to a Mediterranean-like unprocessed foods diet (CLEAN-MED) changes the environment in the intestine. The CLEAN-MED diet includes lots of vegetables, fruits, and whole grains with little sugar or red meat.


Healthy adults aged 18 to 60


Participants will be divided into 2 groups. All will start with a trial week. Participants will log all the food they eat and answer questions about their diet throughout the entire study.

Participants in the short-term group will eat a Western diet for 4 weeks and a CLEAN-MED diet for 4 weeks. Food will be provided for the CLEAN-MED diet. Participants will visit the clinic each week and complete surveys. They will log everything they eat. They will provide blood, urine, and stool samples.

Participants in the long-term group will eat the CLEAN-MED diet for up to 12 months. They will visit the clinic each month and complete surveys. They will log everything they eat. They will provide blood, urine, and stool samples. Some foods will be provided for the first 2 weeks. Participants may choose to have a scan of their body composition every few months.

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In order to be eligible to participate in this study, an individual must meet all of the following criteria:

-Ability of subject to understand and the willingness to sign a written informed consent document

-All genders, races, and ethnicities

-Age 18-60, at the time of consent

-Willingness to adhere to the dietary regimen and report any major stressors that occur during the study (i.e. changing jobs, moving, death of a close relative/friend, etc.)

-Willingness to provide blood and stool specimens as specified

-BMI >=18 and <= 35 kg/m^2

-Access to necessary resources for participating in a technology-based intervention: computer, smartphone, internet access, etc.

-Has the ability/transportation methods to attend on-site visits

-For 50 of the 60 participants in short-term cohort and for 40 of the 50 participants in the long-term cohort: Currently following a Western diet with PREDIMED-17 MedDiet score <= 7 for >= 1 months and a CLEAN-MED NOVA score of >= 35% kcal in NOVA 4 category with >= 14 items/week in NOVA 4

-For 10 of the 60 participants in short-term cohort and for 10 of the 50 participants in the long-term cohort: Currently following a Western diet with PREDIMED-17 MedDiet score <= 10 for >= 1 months and a CLEAN-MED NOVA score of >= 20% kcal in NOVA 4 category with >= 7 items/week in NOVA 4

-CLEAN-MED Logging Score of >= 43 after initial trial week to continue in the study for the randomization step

-For long-term cohort only: Have resources and capability to consume freshly-cooked (i.e. not pre-packaged or frozen) meals


An individual who meets any of the following criteria will be excluded from participation in this study, at the discretion of the PI:

-Current use of medications or dietary supplements for weight or appetite control, whether prescribed or not, including laxatives (within the last 4 weeks)

-Currently eating a vegan, vegetarian, keto or other restrictive diet plan, or food allergies that would affect eating the study diet, at the discretion of the PI

-Active cardiovascular disease (in past year with myocardial infarction, coronary stent or bypass surgery)

-Diabetes (type 1 and 2) or history of gestational diabetes or on hypoglycemic medications or any other indication

-Kidney disease (eGFR less than 50 mL/min per 1.73 m^2)

-Liver disease (liver transaminase higher than 3 times the normal range for the laboratory)

-Symptomatic gallstones

-History of active cancer in the past 3 years except for squamous or basal cell carcinomas of the skin that have been medically managed by local excision

-Has a diagnosed autoimmune condition (i.e. HIV, lupus, etc.) or other immunosuppressive or immunodeficient state, at the discretion of the PI

-Musculoskeletal disorders precluding regular physical activity

-Consumption of the following drugs: proton pump inhibitors, antidiabetic drugs, cholesterol lowering drugs, SGLT-2 inhibitors, GLP-1 receptor agonist, insulin, Amylin analog, Alpha-glucosidase inhibitor, Dopamine agonist, Bile acid sequestrant, corticosteroids, methotrexate or immunosuppressive cytotoxic agents

-Some types of abdominal surgery, including bariatric surgery, or severe intestinal problems (by discretion of study physician), including:

--Inflammatory bowel disease (IBD) including ulcerative colitis (mild-moderate- severe), Crohn s disease (mild-moderate-severe), or indeterminate colitis;

--Irritable bowel syndrome (IBS) (moderate-severe);

--Persistent, infectious gastroenteritis, colitis or gastritis, persistent or chronic diarrhea of unknown etiology, Clostridium difficile infection (recurrent) or Helicobacter pylori infection (untreated);

--Chronic constipation

-Consumes more than 3 alcoholic beverages per day

-Currently receiving or has received antibiotics, antifungals, antivirals, or antiparasitics in past 2 months

-Is currently using or has used probiotic supplements within the last 2 months

-Is currently on a weight-loss program or has experienced a weight change (gain or loss) of greater than 15 pounds in the past 3 months

-Has a history of hospitalization for mental health condition and/or has had a change in depression or anxiety prescription medications within the past 10 weeks (by discretion of study physician)

-Is pregnant or breastfeeding or planning pregnancy within the time of the study

-Subjects who are not fluent in English

-Use of smoking or chewing tobacco, e-cigarettes, cigars, or other nicotine-containing products, or cannabis

-Regular use of prescription opiate pain medication

-Weight <100 lbs

-Acute disease, defined as the presence of a moderate or severe illness with or without fever, at the time of enrollment

-Inability to communicate effectively with study personnel

-Lack of commitment with the intervention or non-compliance (at the discretion of the investigator)

-Eating disorders

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Not Provided

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Principal Investigator

Referral Contact

For more information:

Karen M. Frank, M.D.
National Institutes of Health Clinical Center (CC)
(301) 828-7383

Crystal K. Awuah
National Institutes of Health Clinical Center (CC)
National Institutes of Health
Building 10
Room 10D10
10 Center Drive
Bethesda, Maryland 20892
(301) 594-9490

Office of Patient Recruitment
National Institutes of Health Clinical Center (CC)
Building 61, 10 Cloister Court
Bethesda, Maryland 20892
Toll Free: 1-800-411-1222
Local Phone: 301-451-4383
TTY: TTY Users Dial 7-1-1

Clinical Trials Number:


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