Crohn’s disease is an inflammatory bowel disease that causes inflammation and irritation in the digestive tract. It can affect any part of the gastrointestinal tract, from the mouth to the anus, but it most commonly impacts the end of the small intestine and the beginning of the colon. Some of the most common symptoms of Crohn’s disease include abdominal pain, diarrhea, fatigue, weight loss, and malnutrition. The exact causes of Crohn’s disease are unknown, but it likely involves a combination of genetic, immunological and environmental factors. There has been much interest in whether diet can impact the symptoms and progression of Crohn’s disease. In particular, there has been debate around whether gluten, a protein found in wheat, barley and rye, worsens Crohn’s disease. This article will examine the evidence around whether gluten affects Crohn’s disease.
What is gluten and how is it related to Crohn’s disease?
Gluten is a general name for the proteins found in wheat, rye, and barley. The two main proteins that make up gluten are gliadin and glutenin. When flour and water are mixed together and baked, the gluten proteins form elastic strands that give bread its chewy texture. People with celiac disease have an autoimmune reaction to gluten that damages their small intestine. This leads to symptoms like diarrhea, bloating, and weight loss.
Some research has suggested that the inflammation involved in celiac disease and Crohn’s disease may be connected. This has led to theories that a gluten-free diet may help improve Crohn’s disease symptoms, even in people who do not have celiac disease. However, the evidence on whether gluten impacts Crohn’s disease remains unclear.
Celiac disease vs. gluten sensitivity vs. wheat allergy
It’s important to understand the differences between celiac disease, gluten sensitivity (also called non-celiac gluten sensitivity), and wheat allergy:
- Celiac disease is an autoimmune disorder that causes damage to the small intestine when gluten is consumed. It affects around 1% of the population.
- Non-celiac gluten sensitivity involves gluten-related symptoms like diarrhea and abdominal pain, but without the intestinal damage seen in celiac disease. It affects 5-13% of the population.
- Wheat allergy is an allergic reaction to wheat proteins, not just gluten. Symptoms usually come on quickly and can include hives, breathing difficulties, and even anaphylaxis.
So while celiac disease is specifically triggered by an immune reaction to gluten, other conditions like non-celiac gluten sensitivity and wheat allergy may involve reactions to other wheat components besides gluten.
Research on the gluten-Crohn’s disease connection
Several studies have aimed to determine whether gluten impacts inflammation or symptoms in patients with Crohn’s disease:
Cross-reactivity between anti-gliadin and anti-Saccharomyces cerevisiae antibodies
Some research has focused on the immune response in celiac disease and Crohn’s disease. People with Crohn’s disease often produce antibodies against Saccharomyces cerevisiae, a yeast found in bread. There is some crossover (called cross-reactivity) between these antibodies and antibodies formed against gliadin, one of the main proteins in gluten. This suggests some similarity between the immune reactions in celiac disease and Crohn’s disease. However, these antibodies are found in only around 15-20% of Crohn’s patients, so their clinical significance for most patients is uncertain.
Small trials of the gluten-free diet
There have been a few small clinical trials testing the effect of a gluten-free diet in Crohn’s disease patients without celiac disease:
– A 1990 study had 8 Crohn’s disease patients follow a gluten-free diet for 6 months. 4 out of 8 patients saw significant improvement in symptoms like abdominal pain and diarrhea.
– A 2012 study in Japan put 19 Crohn’s disease patients on a gluten-free diet for 12 months. They found minimal changes in Crohn’s disease symptoms or inflammation.
– A 2015 study had 47 Crohn’s disease patients follow a low-gluten diet for 48 weeks. The diet did not result in significant changes in intestinal inflammation or Crohn’s disease symptoms.
Overall these trials had mixed results, with some isolated cases of improvement but no consistent benefit from eliminating gluten. The studies were limited by their very small sample sizes.
Analyses in large patient databases
A few analyses have examined large databases of medical records to compare Crohn’s outcomes in patients with and without celiac disease:
– A 2010 study looked at 2000 Crohn’s patients, 139 of whom had celiac disease. Rates of surgical treatment for Crohn’s were lower in patients who also had celiac disease.
– A 2016 study examined over 800 Crohn’s disease patients. Around 7% also had celiac disease. These patients were diagnosed with Crohn’s at a younger age, but there were no major differences in Crohn’s disease severity or location.
These database analyses suggest celiac disease may potentially have some small impact on Crohn’s presentation and progression. However, they are limited by inconsistent diagnostic criteria over time and difficulty controlling for all confounding factors.
Potential reasons for the mixed study results
There are several potential explanations for why the research on gluten and Crohn’s has produced such mixed results:
Gluten may only affect a subset of patients
It could be that gluten only impacts disease activity for certain Crohn’s patients. Those with overlap between Crohn’s disease and celiac may be more likely to improve on a gluten-free diet. The very small sample sizes in most studies make it hard to determine if gluten only affects a subset of Crohn’s patients. Larger studies are needed.
Other wheat components could play a role
Removing gluten from the diet typically means removing or reducing intake of wheat overall. Some research suggests that non-gluten wheat proteins may also be relevant for gastrointestinal symptoms. So some benefits seen with gluten elimination may actually be related to reduction of other wheat components like fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPS) and amylase-trypsin inhibitors (ATIs).
The low-gluten diet is complex
In most studies, patients do not follow a true gluten-free diet, but rather a “low-gluten diet” that minimizes gluten intake. There are no standardized definitions for what constitutes a low-gluten diet. The level of gluten restriction likely varies widely between patients in these trials, making study results more inconsistent.
Diet changes could impact results
When following a gluten-free or low-gluten diet, patients often make many other changes to their diet and lifestyle. Changes in dietary fiber or intake of anti-inflammatory foods could influence Crohn’s symptoms, rather than gluten specifically. Most studies try to control patients’ medications but cannot control all diet and lifestyle factors.
Nocebo and placebo effects
Patient expectations may influence how they perceive symptoms on a gluten-free diet. Those who strongly believe gluten is harmful may report improvements due to the “placebo effect.” On the flip side, those who do not expect benefits could experience a “nocebo effect” leading to worse symptoms. Larger blinded, placebo-controlled studies are needed to account for these placebo and nocebo effects.
Underlying celiac disease
Some Crohn’s patients following gluten-free diets may have undiagnosed celiac disease. Eliminating gluten would clearly benefit disease activity in these patients. Better screening is needed to determine if underlying celiac is contributing to positive outcomes in these studies.
Expert opinions on the gluten-Crohn’s disease link
With the research still unclear, many experts hesitate to make firm recommendations about gluten and Crohn’s disease:
“There are not enough data to support this [a gluten-free diet] as a general recommendation.” – Dr. David T. Rubin, University of Chicago
“A gluten-free diet is likely helpful in only a small subset of patients with Crohn’s disease.” – Dr. Corey A. Siegel, Dartmouth College
“We do not have definitive evidence to recommend a gluten-free diet in Crohn’s disease patients. But it may be reasonable to suggest a trial of a gluten-free diet in a subgroup of patients.” – Dr. Konstantinos Papamichael, University of Manchester
Overall, most experts agree that there is currently insufficient evidence to broadly recommend elimination of gluten for management of Crohn’s disease. However, a gluten-free diet may be worth considering on an individual basis in some patients with Crohn’s symptoms that overlap with celiac disease. More research is still needed.
Potential risks of a gluten-free diet for Crohn’s patients
While there could be benefits for some Crohn’s patients removing gluten from their diet, there are also potential downsides:
- Nutritional deficiencies – Gluten-free substitute foods often lack vitamins, minerals, and fiber. A gluten-free diet has been linked to lower intakes of iron, calcium, zinc, magnesium, folate, niacin, and fiber in celiac disease patients.
- Higher fat/sugar intake – To provide palatability in the absence of gluten, gluten-free products sometimes contain more fat, sugar, and salt. This may contribute to weight gain and worse metabolic health.
- Higher cost – On average, gluten-free foods cost 2-3 times more than their gluten-containing counterparts. The increased financial burden could lead some patients to forgo healthy foods.
- Social challenges – Adhering to a strict gluten-free diet can present difficulties in social situations like dining out with friends or traveling.
For Crohn’s patients who do not definitively have celiac disease or gluten sensitivity, the potential quality of life and nutritional risks may outweigh limited benefits from gluten elimination.
Tips for Crohn’s patients considering going gluten-free
For Crohn’s disease patients who decide to try removing gluten from their diet, there are some key recommendations:
- Consult your physician and/or dietitian to create a meal plan. Make sure any new diet is nutritionally complete.
- Work with a gastroenterologist to rule out celiac disease or wheat allergy with testing before eliminating gluten.
- Focus on whole, naturally gluten-free foods like fruits, vegetables, legumes, nuts, seeds, and lean proteins.
- Read labels carefully to check for hidden sources of gluten like soy sauce and preservatives.
- Look for gluten-free oats and pseudocereals like quinoa and buckwheat to increase fiber.
- Fortify your diet with extra calcium, iron, and B vitamins by including dairy, eggs, leafy greens, citrus fruits, and beans.
- Limit gluten-free cookies, breads, and snacks high in fat, sugar, and salt.
- Give any diet change at least 4 weeks to determine if symptoms improve.
Following these tips can help minimize risks and improve chances of successfully identifying if gluten triggers Crohn’s symptoms.
Conclusion
Current evidence on the effects of gluten on Crohn’s disease remains limited and inconsistent. Some patients with overlap between Crohn’s and celiac disease may benefit from gluten restriction. However, there is insufficient evidence to recommend eliminating gluten broadly in Crohn’s patients, especially given potential nutritional and quality of life downsides. Individuals with Crohn’s who decide to pursue a gluten-free diet should do so carefully in partnership with their healthcare team. Larger, long-term randomized controlled studies directly comparing gluten-free and gluten-containing diets are needed to provide clearer guidance on the role of gluten in managing this challenging condition.
