Diet TherapyNCT05411120
Mediterranean-like Unprocessed (CLEAN-MED) Diet Intervention Study of the Gut Microbiome of Healthy Adults
A study testing Western Diet and CLEAN-MED in people with Diet Therapy, run by National Institutes of Health Clinical Center (CC) at 1 site in United States.
Trial summary
Background: 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. Read more about this study
- Who is it for?
- Ages 18 to 60 yearsHealthy volunteers can take part
- Conditions the study is for
- Diet Therapy
- What is being tested?
- Western Diet and CLEAN-MED
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 160 participants
- Where
- 1 siteUnited States
- Study dates
- 26 Aug 2022to 5 Feb 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 60 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- 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
- 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
Show all 12Show fewer
- 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
Who cannot join
- 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)
Show all 31Show fewer
- 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
Trial locations and contacts
1 site in 1 country.
United States1 site
National Institutes of Health Clinical Center
Bethesda, Maryland, 20892
About this study
Background:
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.
Read more
Objective:
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.
Eligibility:
Healthy adults aged 18 to 60
Design:
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.
Read the detailed description
Study Description:
This study (called the CLEAN-MED Diet Study) seeks to examine associations between the gut microbiome, well-being, and adherence to a Mediterranean-like unprocessed food diet. The premise of this study is based on the well-known health benefits of a healthy Mediterranean diet and the potential role that the gut microbiota may serve as a factor in health and disease. The study will recruit healthy outpatient adults, who agree to adhere to a strict Mediterranean-like diet with unprocessed foods, meticulously log their food intake and perceived quality of life using provided questionnaires/tools, and who agree to collect periodic biological samples for analysis. The study will consist of: (1) a short-term cohort who will complete a crossover study design with their habitual Western diet for 4 weeks and the intervention Mediterranean-like unprocessed food diet for 4 weeks (with CLEAN-MED diet food provided by the NIH metabolic kitchen), and (2) a long-term cohort who will continuously adhere to the Mediterranean-like unprocessed food diet for 12 months, following assessment of their baseline diet (with some CLEAN-MED diet foods provided for up to the first 2 weeks of the long-term study, after which the participants must provide their own food).
Objectives:
Primary Objective:
-The primary objective is to measure changes within the gut microbiome in healthy adults who adhere to a Mediterranean-like unprocessed food diet plan.
Secondary Objectives:
- Identify associations between Mediterranean-like unprocessed food diet adherence and psychosocial variables, such as perceived quality of life.
- Identify associations between changes in the gut microbiome and additional biomarkers.
Tertiary Objective:
-Measure the level of adherence to the diet given a strict request for data submission.
Endpoints:
Primary Endpoint:
-Measure changes in gut microbiota composition and functionality from periodic stool sampling using either 16S rRNA and/or shotgun sequencing.
Secondary Endpoints:
- Identify associations between Mediterranean-like unprocessed food diet adherence with perceived quality of life using surveys/questionnaires.
- Measure biomarkers in various biological specimens (stool, blood, and urine) using the pertinent biochemical assays.
- Conditions
- Diet Therapy
- Being tested
- Western Diet, CLEAN-MED
- Keywords
- Immune System, Gastrointestinal Tract
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Western DietOther
Western Diet is by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy and sweets, fried foods, conventionally-raised animal products, butter and other high-fat dairy products, and low intakes of fruits, vegetables, whole grains.
CLEAN-MEDOther
Mediterranean like diet is a high consumption of vegetables, oil and moderate consumption of protein, with no processed foods.
| Study group | Role | What they receive |
|---|---|---|
| Long-term a Intervention: CLEAN-MED | Experimental | Study arm will consume a Mediterranean like diet, while tracking their food intake for 12 months Receives: Other: CLEAN-MED |
| Short-term, Western Diet, high MedDiet score a Intervention: C | Experimental | Study arm will consume a Mediterranean like diet, while tracking their food intake for 9 weeks, With high MEdDIet score. Receives: Other: Western Diet |
| Short-term, Western Diet, high MedDiet score a Intervention: W | Experimental | Study arm will consume a Mediterranean like diet, while tracking their food intake for 9 weeks, With high MEdDIet score. Receives: Other: CLEAN-MED |
| Short-term, Western Diet, low MedDiet score a Intervention: CL | Experimental | Study arm will consume a western diet eating as they normally would for 9 weeks. With low MEdDIet score. Receives: Other: Western Diet |
| Short-term, Western Diet, low MedDiet score a Intervention: We | Experimental | Study arm will consume a Mediterranean like diet, while tracking their food intake for 9 weeks. With low MEdDIet score. Receives: Other: CLEAN-MED |
What is being measured
The primary outcome is the main question the study is designed to answer.
The primary objective is to assess changes in gut microbiome associated with a Mediterranean-like and unprocessed food diet compared to a habitual Western diet in healthy adults.
-Dietary intake via Dietary History Questionnaire (DHQ) III -PREDIMED MedDiet Score -Landry MedDiet Score -The CLEAN-MED NOVA score -Healthy Eating Index (HEI)-2015 -Weight change -Gut microbiome as measured by 16S rRNA analysis of frequent stool collections -Shotgun sequencing will include fungal and viral sequences -Microbial functional pathway analyses
Measured: 9 weeks (Short Term) 12 months (long Term)
Secondary outcomes (2)
Measure biomarkers in various bodily specimens (stool, blood, etc.) using the pertinent biochemical assays.
Measured: 24 months
Identify associations between Mediterranean-like unprocessed food diet adherence with perceived quality of life.
-Daily assessment: CLEAN-MED Office for National Statistics (ONS) survey, 6 questions -Longer assessment: 36-Item Short Form Health Survey (SF-36) for health-related quality of life -Associations of changes in well-being with dietary patterns -Associations of changes in well-being with gut microbiota composition
Measured: 24 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Jun 2022
- Study start26 Aug 2022
- Primary completion4 Feb 2026
- Study completion5 Feb 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Diet TherapyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 160 participants (actual)
Sponsor and investigators
- Lead sponsor
- National Institutes of Health Clinical Center (CC)
- Sponsor type
- US National Institutes of Health
- Responsible party
- Sponsor
- Investigators
- David B Sacks, M.D., Principal investigator, National Institutes of Health Clinical Center (CC)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05411120
- Sponsor's protocol ID
- 10000871
- Other IDs
- 000871-CC
- Status last verified
- 4 Mar 2026
- First submitted
- 4 Jun 2022
- Last updated
- 6 Mar 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided: protocol was silent
Study at a glance
From the registry record, last updated by the sponsor on 6 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Mediterranean-like Unprocessed (CLEAN-MED) Diet Intervention Study of the Gut Microbiome of Healthy Adults
- ClinicalTrials.gov ID
- NCT05411120
- Acronym / sponsor ID
- 10000871
- Conditions
- Diet Therapy
- Keywords
- Immune System, Gastrointestinal Tract
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 160 participants (actual)
- Lead sponsor
- National Institutes of Health Clinical Center (CC)US National Institutes of Health
- Study start
- 26 Aug 2022 (actual)
- Primary completion
- 4 Feb 2026 (actual)
- Study completion
- 5 Feb 2026 (actual)
- First posted
- 9 Jun 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Background:
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.
Objective:
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.
Eligibility:
Healthy adults aged 18 to 60
Design:
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.
Detailed description
Study Description:
This study (called the CLEAN-MED Diet Study) seeks to examine associations between the gut microbiome, well-being, and adherence to a Mediterranean-like unprocessed food diet. The premise of this study is based on the well-known health benefits of a healthy Mediterranean diet and the potential role that the gut microbiota may serve as a factor in health and disease. The study will recruit healthy outpatient adults, who agree to adhere to a strict Mediterranean-like diet with unprocessed foods, meticulously log their food intake and perceived quality of life using provided questionnaires/tools, and who agree to collect periodic biological samples for analysis. The study will consist of: (1) a short-term cohort who will complete a crossover study design with their habitual Western diet for 4 weeks and the intervention Mediterranean-like unprocessed food diet for 4 weeks (with CLEAN-MED diet food provided by the NIH metabolic kitchen), and (2) a long-term cohort who will continuously adhere to the Mediterranean-like unprocessed food diet for 12 months, following assessment of their baseline diet (with some CLEAN-MED diet foods provided for up to the first 2 weeks of the long-term study, after which the participants must provide their own food).
Objectives:
Primary Objective:
-The primary objective is to measure changes within the gut microbiome in healthy adults who adhere to a Mediterranean-like unprocessed food diet plan.
Secondary Objectives:
- Identify associations between Mediterranean-like unprocessed food diet adherence and psychosocial variables, such as perceived quality of life.
- Identify associations between changes in the gut microbiome and additional biomarkers.
Tertiary Objective:
-Measure the level of adherence to the diet given a strict request for data submission.
Endpoints:
Primary Endpoint:
-Measure changes in gut microbiota composition and functionality from periodic stool sampling using either 16S rRNA and/or shotgun sequencing.
Secondary Endpoints:
- Identify associations between Mediterranean-like unprocessed food diet adherence with perceived quality of life using surveys/questionnaires.
- Measure biomarkers in various biological specimens (stool, blood, and urine) using the pertinent biochemical assays.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 5
| Arm | Type | Receives |
|---|---|---|
| Long-term a Intervention: CLEAN-MED | Experimental | Other: CLEAN-MEDStudy arm will consume a Mediterranean like diet, while tracking their food intake for 12 months |
| Short-term, Western Diet, high MedDiet score a Intervention: C | Experimental | Other: Western DietStudy arm will consume a Mediterranean like diet, while tracking their food intake for 9 weeks, With high MEdDIet score. |
| Short-term, Western Diet, high MedDiet score a Intervention: W | Experimental | Other: CLEAN-MEDStudy arm will consume a Mediterranean like diet, while tracking their food intake for 9 weeks, With high MEdDIet score. |
| Short-term, Western Diet, low MedDiet score a Intervention: CL | Experimental | Other: Western DietStudy arm will consume a western diet eating as they normally would for 9 weeks. With low MEdDIet score. |
| Short-term, Western Diet, low MedDiet score a Intervention: We | Experimental | Other: CLEAN-MEDStudy arm will consume a Mediterranean like diet, while tracking their food intake for 9 weeks. With low MEdDIet score. |
Who may qualify
- Ages
- 18 to 60 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (12 listed)
- 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
- 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
Key exclusion criteria (31 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Western DietWestern Diet is by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy and sweets, fried foods, conventionally-raised animal products, butter and other high-fat dairy products, and low intakes of fruits, vegetables, whole grains. | Other | Short-term, Western Diet, high MedDiet score a Intervention: C, Short-term, Western Diet, low MedDiet score a Intervention: CL |
| CLEAN-MEDMediterranean like diet is a high consumption of vegetables, oil and moderate consumption of protein, with no processed foods. | Other | Long-term a Intervention: CLEAN-MED, Short-term, Western Diet, high MedDiet score a Intervention: W, Short-term, Western Diet, low MedDiet score a Intervention: We |
Primary outcome
The primary objective is to assess changes in gut microbiome associated with a Mediterranean-like and unprocessed food diet compared to a habitual Western diet in healthy adults.
Time frame: 9 weeks (Short Term) 12 months (long Term)
-Dietary intake via Dietary History Questionnaire (DHQ) III -PREDIMED MedDiet Score -Landry MedDiet Score -The CLEAN-MED NOVA score -Healthy Eating Index (HEI)-2015 -Weight change -Gut microbiome as measured by 16S rRNA analysis of frequent stool collections -Shotgun sequencing will include fungal and viral sequences -Microbial functional pathway analyses
2 secondary outcomes
Measure biomarkers in various bodily specimens (stool, blood, etc.) using the pertinent biochemical assays.
Time frame: 24 months
Identify associations between Mediterranean-like unprocessed food diet adherence with perceived quality of life.
Time frame: 24 months
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 6 Mar 2026.
- NIH Clinical Center Detailed Web PageLink provided by the sponsor.
- Individual participant dataSharing planned: Undecided. protocol was silent
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Healthy Volunteers
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
David B Sacks, M.D. principal investigator
National Institutes of Health Clinical Center (CC)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Western Diet and CLEAN-MED in people with Diet Therapy, run by National Institutes of Health Clinical Center (CC) at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 12 inclusion and 31 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 6 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
The primary objective is to assess changes in gut microbiome associated with a Mediterranean-like and unprocessed food diet compared to a habitual Western diet in healthy adults. (time frame: 9 weeks (Short Term) 12 months (long Term)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 Mar 2026.