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). |
Professional Abstract
Objective
To compare the effectiveness of the Mediterranean diet (MD) and the Specific Carbohydrate Diet (SCD) in resolving symptoms among patients with Crohn’s disease
Study Design
| Design Element | Description |
|---|---|
| Design | Randomized controlled trial |
| Population | 191 adults over age 18 with Crohn’s disease and mild to moderate symptoms |
| Interventions/ Comparators |
|
| Outcomes |
Primary: symptomatic remission, defined as a short Crohn’s Disease Activity Index score of less than 150 in the absence of initiation of or increase in any Crohn’s disease medications, at week 6 Secondary: symptomatic remission at week 12; clinical remission defined as a Crohn’s Disease Activity Index score of less than 150; health-related quality of life, pain, fatigue, sleep disturbance, and social isolation at 6 and 12 weeks |
| Timeframe | 6-week follow-up for primary outcome |
This randomized controlled trial compared the effectiveness of two diets on achieving symptomatic and clinical remission and improving patient-reported outcomes among adults with Crohn’s disease. Both diets allow large amounts of fresh fruits and vegetables. The MD allows many types of foods but may limit amounts. For example, it includes large amounts of nuts, fish, whole grains, and olive oil but limits red meat and processed foods. The SCD lists foods that are and are not allowed. It allows fresh, unprocessed meats but not canned or processed foods, most dairy, or grains.
Researchers randomized patients to follow either the MD or SCD for 12 weeks. During the first six weeks, patients received weekly food deliveries of three prepared meals and two snacks for each day for their assigned diet. After six weeks, patients could choose to pay for weekly prepared meals or continue the diet on their own. The study website provided guidance for meal planning, and a dietician was available to answer questions.
The study included 191 adults with Crohn’s disease from across the United States. Of these, 91% were White, 4% were Black, 1% were Asian, and 4% reported other, more than one race, or did not report a race; 4% were Hispanic. The average age was 40, and 63% were female.
Patients completed surveys at the start of the study and again at 6 and 12 weeks. Patients reported their symptoms online daily. At weeks 3, 6, 9, and 12, patients reported their adherence to their assigned diet in the previous week.
Patients, doctors, and representatives from the Crohn’s & Colitis Foundation helped plan and conduct the study.
Results
At six weeks, 64% of patients on the MD and 68% on the SCD reported full adherence to the diet. At 12 weeks, 42% of patients on MD and 40% on SCD reported full adherence to the diet.
The two diets did not differ significantly in any outcomes at 6 or 12 weeks. At six weeks, 44% of patients on the MD and 47% on the SCD achieved symptomatic remission, and 48% on the MD and 49% on the SCD achieved clinical remission. With both diets, patients reported fewer symptoms, higher health-related quality of life, and less pain, fatigue, sleep disturbance, and social isolation (all p<0.03) at six weeks.
Limitations
Providing prepared meals during the first six weeks may have optimized adherence and overestimated the effectiveness of these diets in general practice. Most patients in the study were White. Results may differ for people from other racial backgrounds.
Conclusions and Relevance
In this study, regardless of diet, more than 40% of patients with Crohn’s disease had symptomatic and clinical remission after six weeks, with no significant differences between the diets.
Future Research Needs
Future research could compare the MD and SCD with other diets recommended in the treatment of Crohn’s disease.
| 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.
Journal Citations
Results of This Project
Related Journal Citations
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.