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Both the Mediterranean diet and the Specific Carbohydrate diet were effective for symptom reduction in patients with Crohn's disease, a randomized clinical trial demonstrated.

At week 6, symptomatic remission was achieved by 44% of patients on the Mediterranean diet and by 47% of those following the Specific Carbohydrate diet, reported James D. Lewis, MD, of the University of Pennsylvania in Philadelphia at the virtual Crohn's and Colitis Congress.

And clinical remission defined by the Crohn's Disease Activity Index also was observed in similar numbers, at 48% for the Mediterranean diet and 49% for the Specific Carbohydrate diet.

"One of the unique features of this study was that it was patient derived," Lewis said. Specifically, the study came about because of a patient question posed in the Crohn's & Colitis Foundation's IBD Partners patient-powered research network.

"When we asked patients with inflammatory bowel disease [IBD] what they felt were the most important questions, they wanted to know what role diet should have, and particularly the Specific Carbohydrate diet, for managing their Crohn's disease," he said.

The diet was developed in the 1920s as a treatment for celiac disease, and has been popular among individuals with IBD. The diet is based on the theory that complex carbohydrates encourage the growth of unhealthy bacteria in the gut, which then produce byproducts that encourage inflammation.

To evaluate that diet, Lewis and colleagues decided to use the Mediterranean diet as a comparator because of its known health-associated benefits in the general population, with reductions in cardiovascular disease, cancer, and all-cause mortality, and also in Crohn's disease patients, where it has been associated with both a lower incidence of disease and, in some studies, improvements in symptoms and quality of life.

The Specific Carbohydrate diet is characterized by a high intake of unprocessed meat, poultry, fish, shellfish, and eggs; most vegetables no matter how they are prepared; most fruits and nuts; and avoidance of grains, dairy, and sweeteners other than honey.

The Mediterranean diet is characterized by a high intake of olive oil, fruits, vegetables, nuts, and cereals; moderate intake of fish, poultry, and wine; and limited intake of red and processed meats and sweets.

The study was a 12-week parallel-group randomized trial that included 194 patients. Participants had mild-to-moderate Crohn's disease defined as a short Crohn's disease activity index score of 176 to 399, and were on stable doses of medications. Exclusion criteria included pregnancy, presence of an ostomy, symptomatic strictures, or recent Clostridium difficile colitis.

For the first 6 weeks of the study, patients were provided with prepared meals that were essentially "heat and eat;" they then prepared their own meals, adhering to their diet, for weeks 7 through 12.

A total of 60% of the participants had nonstricturing, nonpenetrating disease, 25% had disease of the ileum alone, and one-third had previously undergone intestinal surgery.

"This was a fairly medication-experienced population, with just over 50% taking a biologic at the time of screening," Lewis said.

Patients were not required to have evidence of ongoing inflammation, but about half did, based on having an elevated C-reactive protein (CRP) or calprotectin, or colonoscopy-confirmed inflammation within 3 months of screening.

Secondary outcomes at week 6 included calprotectin response, defined as a reduction in this marker to less than 250 µg/g and at least by 50% from baseline. That outcome was met by 31% and 35% of the Mediterranean and Specific Carbohydrate diet groups, respectively. Few patients in either group had CRP responses (4% and 5%, respectively), defined as a reduction in high sensitivity CRP to less than 5 mg/L.

Quality of life measures at week 6, including fatigue, pain, sleep, and social isolation improved significantly in both groups, without any differences between the two groups.

At week 12, symptomatic remission was seen in 40% of the Mediterranean diet group and in 42% of the Specific Carbohydrate diet group, and clinical remission rates were 47% and 40%.

On a prespecified subgroup analysis, the two diets had no significant differences in the rate of symptomatic remission among patients with or without definitive evidence of inflammation at the time of screening.

"Both diets were well tolerated despite the increased consumption of fruit and vegetables, which is something that historically we often have told patients with active disease to avoid," he said.

"Based on these findings, if you had to choose between these two diets, for most Crohn's disease patients you might consider the Mediterranean diet, given its other health benefits, although I will say the Specific Carbohydrate diet has never been tested for those other health benefits," he concluded.

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