A New Diet Option for Mild-to-Moderate Crohn’s Disease Shows Promising Results
“What should I eat?” is one of the most common — and frustrating — questions asked by people living with inflammatory bowel disease (IBD). For years, doctors have struggled to give clear, evidence-based answers. Unlike medications, diets are notoriously difficult to study, and large clinical trials focusing on food and IBD have been rare. Now, new research from Stanford Medicine and collaborating institutions offers some of the clearest data yet that diet may play a meaningful role in managing mild-to-moderate Crohn’s disease.
The study, published in Nature Medicine, tested a structured fasting-mimicking diet (FMD) and found that it significantly improved both clinical symptoms and biological markers of inflammation in many patients. Importantly, these improvements were not just based on how patients felt but were backed by measurable changes in blood and stool samples.
Why Diet Has Been Such a Big Question in Crohn’s Disease
Crohn’s disease is a chronic inflammatory condition that affects the digestive tract and currently impacts about one million people in the United States. Symptoms often include diarrhea, abdominal pain, cramping, fatigue, and weight loss, and the disease typically follows a pattern of flare-ups and remissions.
Despite how strongly patients feel that food affects their symptoms, there has been surprisingly little solid evidence to guide dietary recommendations. Most advice has been based on small studies, observational data, or personal experience. For patients with mild Crohn’s disease, treatment options are especially limited. Steroids are the only approved therapy, but their long-term use is discouraged due to serious side effects.
This gap between patient curiosity and scientific evidence is exactly what motivated the Stanford-led research team to explore whether a specific dietary intervention could reliably reduce inflammation.
What the Study Actually Tested
The researchers conducted a national, randomized controlled clinical trial, the gold standard for medical research. A total of 97 adults with mild-to-moderate Crohn’s disease were enrolled across the United States.
Participants were divided into two groups:
- 65 patients followed the fasting-mimicking diet
- 32 patients continued eating their normal diet while maintaining standard medical care
The fasting-mimicking diet was not a constant restriction. Instead, participants followed a five-day calorie-restricted plan once per month for three consecutive months. During those five days, calorie intake was limited to approximately 700 to 1,100 calories per day, and the meals were plant-based. These meals were provided to participants to ensure consistency.
For the remaining days of each month, participants returned to their usual eating habits, making the approach less disruptive than long-term fasting or extreme diet plans.
Improvements in Symptoms Were Hard to Ignore
By the end of the three-month study period, the results were striking. About two-thirds of patients in the fasting-mimicking diet group showed a clear improvement in their Crohn’s symptoms. Many participants experienced benefits after just one cycle of the diet, suggesting that the effects can appear relatively quickly.
In contrast, less than half of the control group reported symptom improvement. Researchers believe these improvements were largely due to the natural ups and downs of Crohn’s disease and the fact that patients continued their usual medications.
Some participants following the fasting-mimicking diet reported temporary fatigue and headaches, which are common during calorie restriction. However, no serious side effects were reported, an important finding when evaluating the safety of any new intervention.
Biological Markers Backed Up the Symptom Changes
One of the most compelling aspects of this study is that improvements were not based solely on self-reported symptoms. Researchers also analyzed blood and stool samples to measure inflammation at a biological level.
A key finding was a significant reduction in fecal calprotectin, a protein found in stool that is widely used as an objective marker of intestinal inflammation. Elevated calprotectin levels are closely linked to active Crohn’s disease, so seeing these levels decline provided strong evidence that inflammation itself was decreasing.
The fasting-mimicking diet group also showed reductions in certain inflammation-promoting lipid mediators derived from fatty acids. Additionally, immune cells collected from these participants produced fewer inflammatory molecules, suggesting a broader calming effect on the immune system.
These changes were far less pronounced in the control group, reinforcing the idea that the diet itself played a direct role.
Why the Fasting-Mimicking Diet Makes Sense Biologically
The fasting-mimicking diet has been studied previously in other contexts, including aging and metabolic health. Earlier research showed that this type of diet could reduce levels of C-reactive protein, a marker of systemic inflammation, especially in people who started with high baseline levels.
Because many Crohn’s patients also have elevated inflammatory markers, the researchers believed this diet could be a good fit. The goal was not to starve the body, but to temporarily shift metabolism in a way that resets inflammatory pathways while still providing essential nutrients.
The research team is now investigating whether changes in the gut microbiome — the community of bacteria living in the digestive tract — may help explain some of the observed benefits.
What This Means for Patients and Doctors
For physicians, this study provides long-awaited evidence to support dietary recommendations for Crohn’s disease. Until now, many doctors had little data to guide conversations about food, despite patients consistently asking for help in this area.
It’s important to note that the fasting-mimicking diet is not a replacement for medical treatment, and it may not be suitable for everyone. Factors like nutritional status, disease severity, and other medical conditions need to be considered. Still, the findings suggest that dietary interventions can produce real, measurable improvements, especially for patients with milder forms of the disease.
Limitations and Conflicts to Be Aware Of
Like all studies, this one has limitations. The trial lasted only three months, so long-term effects remain unknown. Participants also knew which diet they were following, which can influence perceived symptom improvement.
Additionally, one of the authors, Valter Longo, has a financial interest in L-Nutra, the company that provided the fasting-mimicking meals, and holds patents related to the diet. This disclosure is important for transparency and highlights the need for independent replication of the findings.
The Bigger Picture of Diet and Inflammatory Bowel Disease
This study adds to a growing body of evidence suggesting that targeted dietary strategies can influence inflammation in meaningful ways. While no single diet works for everyone with Crohn’s disease, structured approaches like the fasting-mimicking diet may offer a new tool — especially for patients looking to avoid or delay steroid use.
As research continues, future studies may help identify which patients benefit the most, how often the diet should be used, and whether it can be combined with other treatments for even better results.
Research paper reference:
https://www.nature.com/articles/s41591-025-04173-w
