Results Summary

What was the research about?

People with Crohn’s disease have ongoing stomach pain, cramping, and diarrhea. A person’s diet can affect symptoms. But questions remain about which diets help the most to reduce symptoms.

In this study, the research team compared the effects of two diets on symptoms and quality of life in patients with Crohn’s disease:

  • The Mediterranean diet, or MD allows many types of foods, but limits the amount eaten. It’s high in fresh fruits, vegetables, nuts, fish, whole grains, and olive oil and limits red meat and processed foods.
  • The Specific Carbohydrate Diet, or SCD lists foods that are and aren’t allowed. It allows fruits, vegetables, unprocessed meats, and some lactose-free dairy, but doesn’t allow some sugars and starches like potatoes or yams.

What were the results?

At six weeks, 64 percent of patients on the MD and 68 percent on the SCD had stayed on the diet. At 12 weeks, 42 percent on the MD and 40 percent on the SCD had stayed on the diet.

The two diets didn’t differ in how they affected patients’ health after 6 and 12 weeks. At six weeks, about 45 percent of patients on each diet reported feeling better and no longer had symptoms of diarrhea and stomach pain. Overall, patients on each diet reported improved quality of life and less pain, fatigue, sleep disturbance, and feelings of isolation from family and friends at six weeks.

Who was in the study?

The study included 191 people with Crohn’s disease from across the United States. All had mild to moderate symptoms. Of these, 91 percent were White, 4 percent were Black, 1 percent were Asian, and 4 percent reported other, more than one, or didn’t report a race; 4 percent were Hispanic. The average age was 40, and 63 percent were women.

What did the research team do?

The research team assigned patients by chance to either the MD or SCD. Every week for six weeks, patients had three prepared meals and two snacks per day delivered to their homes. After six weeks, patients could either pay for the prepared meals or continue the diet on their own. The study website had support for meal planning. A dietician was available to answer questions.

Patients completed surveys at the start of the study and 6 and 12 weeks later. Patients reported their symptoms online each day and how much they stayed on their assigned diet at weeks 3, 6, 9, and 12.

Patients, doctors, and staff from the Crohn’s & Colitis Foundation helped to plan and conduct the study.

What were the limits of the study?

Providing meals for the first six weeks of the study may have helped patients stay on the diet. Results may differ in real-word settings. Most patients were White; results may differ for patients of other backgrounds.

Future research could compare the MD and SCD diets with other diets.

How can people use the results?

Patients with Crohn’s disease and their doctors can use the results when considering diets to decrease symptoms.

How this project fits under PCORI’s Research Priorities
IBD Partners formerly was a Network Partner in PCORnet®, the National Patient-Centered Clinical Research Network. PCORnet® has been developed with funding from the Patient-Centered Outcomes Research Institute (PCORI).

Final Research Report

View this project's final research report.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments. 

Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:

  • The reviewers noted that the results of the study could not provide any conclusions on the efficacy of either the Mediterranean diet or specific carbohydrate diet to improve symptoms associated with Crohn’s disease because the diets were not compared to a regular or normal diet. The researchers responded that they considered adding a normal diet condition as a third comparison arm in the study, but they were concerned that participants in this arm would have very high drop-out rates if they received no medical intervention from the trial. High drop out in this one study arm might create the appearance of higher effectiveness for the two experimental diet conditions. Instead, the researchers chose to design the study as a comparative effectiveness trial of two active interventions, and defended their conclusions that the two diets both demonstrated symptomatic remission with no apparent differences between the diets. They did add a note to their conclusions that the study could not demonstrate whether either diet was superior to patients with Crohn’s disease maintaining their usual diets.
  • The reviewers questioned the investigators’ decision to include all patients with Crohn’s disease and mild to moderate symptoms regardless of active inflammation as eligible for the study rather than including only those patients with active inflammation. The researchers explained that some of the testing for active inflammation could delay a patient’s randomization into the study by two weeks or more, so they removed this criterion to reduce the amount of time to study entry.
  • The reviewers asked the researchers to comment on why the overwhelming majority of study participants identified as White, not Hispanic or Latino. The researchers noted that it is common for studies on Crohn’s disease to include a mostly White population, and that the lower prevalence of African-American and Hispanic or Latino patients may be related to the demographics of patients in the participating study centers or the demographics of patients who agreed to participate in this study. The researchers added a study limitation indicating that the generalizability of study results may not extend to non-White races or ethnicities.

Conflict of Interest Disclosures

Project Information

James D. Lewis, MD, MS
Crohn's and Colitis Foundation of America, Inc.
$2,606,273
10.25302/10.2021.PPRND.150731465
Comparative Effectiveness of Specific Carbohydrate and Mediterranean Diets to Induce Remission in Patients With Crohn's Disease

Key Dates

March 2016
October 2022
2016
2021

Study Registration Information

Tags

Has Results
Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
State State The state where the project originates, or where the primary institution or organization is located. View Glossary
Last updated: November 30, 2022