The Mediterranean diet (MD) is associated with both a lower risk of Crohn’s disease (CD) and reduced symptoms after CD diagnosis. The Specific Carbohydrate Diet (SCD) has been popularized as a therapeutic diet consisting of ‘legal’ (allowed) and ‘illegal’ (excluded) foods. Fresh fruits and vegetables, certain legumes, unprocessed meats, and homemade fermented yogurts are examples of allowed foods. Grains, canned produce, smoked meats, and milk are examples of excluded foods. Small, uncontrolled studies have shown improvements in symptoms and bowel inflammation after using the SCD, but larger controlled studies examining the efficacy of the SCD compared to other therapeutic diets have not yet been published.
In this 12-week randomized trial, 194 participants with mild to moderate CD followed the MD or SCD for 12 weeks to compare their effects on symptoms and inflammation. For the first 6 weeks, the participants on the MD received weekly meal deliveries, and those on the SCD received a three-day ‘starter diet’ recommended in the SCD book titled “Breaking the Vicious Cycle”. After the first 6 weeks, the participants received meal planning guidance via the study website, support from a dietitian, and the option of purchasing ongoing meal delivery.
Data from 24-hour dietary recalls completed at baseline and at weeks 6 and 12 of the trial were used to calculate the Alternate Mediterranean Diet Score and Healthy Eating Index 2015. Dietary adherence was assessed every 3 weeks by asking the participants whether they followed the diet all of the time, some of the time, or none of the time.
The primary and secondary outcomes included the following:
symptomatic remission (as indicated by the shortened Crohn's Disease Activity Index)
fecal calprotectin response (indicating reduced intestinal inflammation)
C-reactive protein (CRP) response (indicating reduced systemic inflammation)
Disease-specific questionnaires were used to assess the following:
extraintestinal manifestations of CD
The researchers also analyzed the fecal calprotectin response and CRP response in combination with symptomatic remission. Finally, stool microbiome analysis was performed at baseline and at weeks 6 and 12 of the trial to determine effects on alpha and beta diversity (microbiome measurements).
The participants reported similar adherence to both diets, and both groups significantly increased their consumption of fruits and vegetables, resulting in similar scores on the Healthy Eating Index 2015 and Alternate Mediterranean Diet Score. Both groups experienced similar rates of remission and improvements in fatigue, pain, sleep interference, social isolation, and symptoms as assessed by disease-specific questionnaires. However, CRP did not improve in either group, indicating that the diets may influence symptoms more than inflammation.
During interviews before the trial, the participants indicated that they would be unlikely to continue a restrictive diet for longer than 6 weeks unless they experienced improvements in their symptoms. Therefore, the authors recommended the MD (rather than the SCD), given its numerous health benefits and less restrictive guidelines.
Over the course of the study, 70 participants withdrew, and this could have influenced the results. Although the authors noted that the subgroup of participants with high dietary adherence demonstrated improvements similar to those of the entire group, the withdrawal of participants reduced their sample size enough to affect their statistical analysis. Additionally, improvements in symptoms and remission could be explained by the increased dietary quality rather than exclusion of specific foods.
Of the 31 authors listed on this study, 13 reported one or more potential conflicts of interest.
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