Clinical Center News
August / September 2023

Interested in healthy eating and the mediterranean diet?

Study Investigates Mediterranean Diet's Impact on Gut Biome

a table spread with salmon and other healthy foods
Healthy Eating and the Mediterranean Diet study.

Is a Mediterranean-like diet that eliminates many ultra-processed foods healthier than a Western diet?

The CLEAN-MED diet intervention study was designed to test this concept.

Dr. Karen Frank, Chief of the hospital’s Department of Laboratory Medicine and the principal investigator of the clinical trial, explained that the role of diet in the modulation of gut microbiota has been widely recognized. Trillions of microorganisms, composed of mostly bacteria, but also viruses, bacteriophages, fungi and others, act together with their host to break-down nutrients, influence immunity and possibly have an active role in disease pathogenesis.

“There are now many scientific studies that have associated diet and health, including mental health and we are excited to dig deeper into the biological pathways responsible, as well as the intricate connection between bacteria and human hosts,” said Dr. Frank. The CLEAN-MED diet combines the Mediterranean diet with a diet that utilizes minimally processed foods.

A typical Mediterranean diet includes high intake of vegetables, legumes, fruits, nuts, whole-grain cereals and olive oil; moderate intake of fish and wine; low intake of poultry and dairy; and very low intake of red meat.

This study will follow two groups, a randomized cross-over study design by alternating one month of routine food and one month of food prepared by the NIH metabolic kitchen. The second group of participants will receive education with experienced dieticians, then they cook their own food for a year while receiving guidance from the study team.

Participants will be asked to keep very detailed food logs and photograph the ingredients on their food containers for the study team. Participants will also need to complete a number of surveys and log how they are feeling throughout the study.

This study is enrolling healthy volunteers 18 to 60 years old for a 2-month or 12-month group. Find out how to participate in the study online or call 866-444-3388.

You are now leaving the NIH Clinical Center website.

This external link is provided for your convenience to offer additional information. The NIH Clinical Center is not responsible for the availability, content or accuracy of this external site.

The NIH Clinical Center does not endorse, authorize or guarantee the sponsors, information, products or services described or offered at this external site. You will be subject to the destination site’s privacy policy if you follow this link.

More information about the NIH Clinical Center Privacy and Disclaimer policy is available at