“Doctor, what can I eat?”
For gastroenterologists that care for patients with Crohn’s disease (CD) and ulcerative colitis, this is one of the most common questions asked by our patients. Prior studies have demonstrated that diets high in fruits and vegetables may be protective against developing CD, and diets high in saturated fats and red meat are associated with an increased risk of CD; however, dietary intake of red meat was not associated with relapse of disease. Additionally, studies in pediatric CD have demonstrated the efficacy of enteral nutrition and exclusion diets. Specific diets such as the Specific Carbohydrate Diet (SCD) have been used intermittently by patients with CD but have not been rigorously studied. Until recently, gastroenterologists have not been able to recommend a specific diet for our adult patients.
At DDW 2021, James Lewis and colleagues presented the results of Diet to Induce Remission in Crohn’s Disease (DINE-CD). DINE-CD was a multicenter, randomized trial comparing the efficacy of an SCD versus a Mediterranean diet (MD) over 12 weeks. Sites were recruited from the Clinical Research Alliance of the Crohn’s and Colitis Foundation. Adults with mild to moderate symptoms, defined using the short Crohn’s disease activity index were eligible to participate. Patients could remain on a stable dose of their maintenance medications throughout the 12-week study. Although symptoms alone were used for enrollment, baseline inflammation as assessed by colonoscopy, C-reactive protein (CRP), or fecal calprotectin was confirmed in just under half of patients. Patients were randomized 1:1 to receive either an SCD or MD. Randomization was stratified by baseline biological use. For the first six weeks of the study, patients received prepared foods for their specific assigned diet. For the remaining six weeks, they could purchase the food or prepare it on their own. The primary outcome was symptomatic remission at week 6. Ninety-two patients were assigned to the MD and 99 to SCD. At week 6, remission was achieved by 43.5% of patients receiving an MD vs. 46.5% of patients receiving the SCD (p=ns). Improvement in fecal calprotectin, defined as a value less than 250 mcg/g with a decline by 50% from baseline, was achieved in 30.8 and 34.8% of MD and SCD treated patients, respectively. CRP response rates were low in both groups. A sensitivity analysis was performed to assess whether the presence of confirmed inflammation at baseline affected results. The results were not significantly different in those with or without confirmed inflammation at baseline.
The strengths of the study include the trial design, blocked randomization, inclusion of multiple sites, and providing patients with prepared meals for the first six weeks of the study. The primary weakness of the trial involves the use of symptoms alone as an entry requirement for the investigation. It is well known that there can be a disconnect between a patient’s symptoms and inflammation, as other mechanisms can result in symptoms aside from inflammation (i.e., concurrent irritable bowel syndrome, symptoms due to prior surgery, bacterial overgrowth, and bile salt-induced diarrhea). Additionally, objective markers of inflammation were not the primary endpoint of the study. Nevertheless, a subanalysis revealed that patients with and without confirmed inflammation at baseline had similar responses to the diet. Overall, DINE-CD confirms that both an MD and SCD improve symptoms and biological markers of inflammation in the short term. Follow-up studies will be needed to see if the short-term results were maintained when patients were required to purchase or make their prescribed foods and if symptoms recur when the previous diet is resumed.
This study has several important implications. First, gastroenterologists can finally recommend a specific diet for our patients, either an MD or SCD. A recent retrospective cohort study from Italy also confirmed that an MD improves symptoms, biomarkers of inflammation, and liver steatosis. Additionally, two other prospective studies have demonstrated that an MD prevents late-onset CD. Given the other known health benefits of an MD, as well as simplicity of implementation, an MD should be the preferred diet for patients with CD. Additionally, in patients with an incomplete response to therapy, nutritional therapy with either the MD or SCD can be used to further induce clinical and biologic remission.
Illustration by Jennifer Bogartz