For Crohn’s disease, a diet low in refined carbohydrates and a symptoms-guided diet appeared to help with remission, yet reduction of refined carbohydrates or red meat didn’t reduce the risk of relapse. For ulcerative colitis, solid food diets were similar to control measures.
“The Internet has a dizzying array of diet variants touted to benefit inflammation and IBD, which has led to much confusion among patients, and even clinicians, over what is truly effective or not,” Berkeley Limketkai, MD, PhD, director of clinical research at the Center for Inflammatory Bowel Disease at the University of California, Los Angeles, said in an interview.
“Even experiences shared by well-meaning individuals might not be generalizable to others,” he said. “The lack of clarity on what is or is not effective motivated us to perform this systematic review and meta-analysis.”
The study was published online in Clinical Gastroenterology and Hepatology.
Analyzing diets
Some nutritional therapies, such as exclusive enteral nutrition, have good evidence to support their use in the treatment of IBD, Dr. Limketkai said. However, patients often find maintaining a liquid diet difficult, particularly over a long period of time, so clinicians and patients have been interested in solid food diets as a treatment for IBD.
In 2019, Dr. Limketkai and colleagues conducted a systematic review and meta-analysis of randomized controlled trials focused on solid food diets for IBD that was published with the Cochrane Collaboration. At that time, the data were considered sparse, and the certainty of evidence was very low or low. Since then, several high-quality trials have been published.
For this study, Dr. Limketkai and colleagues conducted an updated review of 36 studies and a meta-analysis of 27 studies that compared a solid food diet with a control diet in patients with Crohn’s disease or ulcerative colitis. The intervention arm had to involve a well-defined diet, not merely a “usual” diet.
Among the studies, 12 evaluated dietary interventions for inducing clinical remission in patients with active Crohn’s disease, and 639 patients were involved. Overall, a low–refined carbohydrate diet was superior to a high-carbohydrate diet or a low-fiber diet. In addition, a symptoms-guided diet, which sequentially eliminated foods that aggravated a patient’s symptoms, was superior to conventional nutrition advice. However, the studies had serious imprecisions and very low certainty of evidence.
Compared with respective controls, a highly restrictive organic diet, a low-microparticle diet, and a low-calcium diet were ineffective at inducing remission of Crohn’s disease. Studies focused on immunoglobulin G-based measures were also inconsistent.
When comparing diets touted to benefit patients with Crohn’s disease, the Specific Carbohydrate Diet was similar to the Mediterranean diet and the whole-food diet, though the certainty of evidence was low. Partial enteral nutrition was similar to exclusive enteral nutrition, though there was substantial statistical heterogeneity between studies and very low certainty of evidence.
For maintenance of Crohn’s disease remission, researchers evaluated 14 studies that included 1,211 patients with inactive disease. Partial enteral nutrition appeared to reduce the risk of relapse, although evidence certainty was very low. In contrast, reducing red meat or refined carbohydrates did not lower the risk of relapse.
“These findings seemingly contradict our belief that red meat and refined carbohydrates have proinflammatory effects, although there are other studies that appear to show inconsistent, weak, or no association between consumption of unprocessed red meat and disease,” Dr. Limketkai said. “The caveat is that our findings are based on weak evidence, which may change as more studies are performed over time.”
For induction of remission in ulcerative colitis, researchers evaluated three studies that included 124 participants with active disease. When compared with participants’ usual diet, there was no benefit from a diet that excluded symptom-provoking foods, fried foods, refined carbohydrates, additives, preservatives, most condiments, spices, and beverages other than boiled water. Other studies found no benefit from eliminating cow milk protein or gluten.
For maintenance of ulcerative colitis remission, they looked at four studies that included 101 patients with inactive disease. Overall, there was no benefit from a carrageenan-free diet, anti-inflammatory diet, or cow milk protein elimination diet.