In 2017, it was estimated that there are 6.8 million people living with IBD worldwide. This disease is more common in Western countries than in Eastern Europe and Asia, although cases have been rising in regions with a historically low IBD prevalence. Interestingly, studies have also shown evidence that risk for developing IBD increases in immigrants from low-prevalence countries to higher-prevalence countries. This suggests a possible influence of diet or other lifestyle factors in IBD development. 

Recent research has emerged focusing on creating clear, evidence-based dietary recommendations for IBD patients.There is currently a scarcity of scientifically-backed dietary guidelines for the management of IBD, and researchers have been working to address this shortage. 

What is IBD?

Inflammatory Bowel Disease (IBD) is a chronic gastrointestinal disease in which immune cells attack the lining of the GI tract, known as the epithelium. This leads to chronic inflammation and can have debilitating consequences for those suffering from the disease. There are two main types of IBD, including:

• Crohn’s disease (CD): Crohn’s disease can cause inflammation in any part of the GI tract, but it is most commonly found in the terminal ileum and colon. CD inflammation can affect multiple parts of the GI system simultaneously. This chronic inflammatory response can cause the bowel wall to thicken, leading to complications such as abscesses or strictures. 
• Ulcerative colitis (UC): In contrast, ulcerative colitis is organ-specific and only occurs in the colon. It affects layers of the GI tract closer to the surface than CD and frequently causes ulcers, otherwise known as open sores, within the large intestine.

Both Crohn’s disease and ulcerative colitis can have debilitating symptoms that affect patients’ day-to-day living. Some common effects of IBD are:

• Severe stomach pain
• Abdominal cramping 
• Urgency for bowel movements
• Diarrhea
• Predisposition to infections
• Bleeding and anemia

Because IBD causes malabsorption of nutrients from food, weight loss and certain nutrient deficiencies can result in patients affected by this disease. In younger patients, growth and development may be negatively affected by IBD-related malnutrition.

Unfortunately, IBD tends to be a relapsing condition that develops tolerance or resistance to various types of treatment. The chronic nature of the inflammation caused by IBD causes damage to affected areas of the GI tract and can therefore predispose to gastrointestinal cancers. 

Risk Factors for IBD

Although the exact mechanism of IBD development remains poorly understood, studies have suggested a combined role of genetics and environmental factors in causing both types of IBD. A genetic cause has been investigated because of increased rates of disease in those who have family history of IBD. More specifically, relatives of an IBD patient are about 10 times more likely to have IBD.

Another risk factor known to predispose to Crohn’s disease specifically is smoking. According to a key study, smoking increases risk for CD twofold when compared to nonsmokers. However, no such association was found between smoking and ulcerative colitis.

Differences in exposure to bacteria throughout one’s life may also have an impact on Crohn’s disease development. The hygiene hypothesis states that minimal exposure to pathogens in early life can lead to the abnormal immune responses involved in IBD later on. However, infection with specific microorganisms has been proposed as a triggering mechanism for IBD development as well. Two of the most common bacterial infections with known associations with IBD are E. coli and H. pylori.

Diet and Predisposition

Another key factor that can cause increased risk for IBD is diet. In particular, a Western diet pattern notorious for high caloric content, refined sugar, unsaturated fat, and fast food has been linked to the development of IBD. Lack of fruits, vegetables, and dietary fiber also negatively affect the GI tract and can play a role in pathogenesis.  

In fact, the Western diet itself has been shown to cause chronic, low-grade inflammation within the gut lining through the release of inflammatory molecules. Poor diet composition can reduce intestinal permeability, making malabsorption disorders such as IBD more likely to occur. Diet may also exert its influence by impacting the balance of microorganisms in the gut microbiome and causing dysbiosis. By decreasing levels of beneficial organisms and increasing presence of detrimental bacteria, a Western diet can wreak havoc on the gut. 

Aside from the composition of the Western diet, the preparation of highly processed foods has also been linked to inflammatory disorders. According to a 2021 study, the use of preservatives and emulsifiers causes increased rates of Crohn’s disease by disrupting the protective mucus layer of the intestines and affecting translocation of bacteria. However, the same effect was not found with ulcerative colitis patients.

Diet and Prevention

Although dietary factors can increase chances of developing IBD, on a more positive note, diet can also be used as a management strategy alongside medical treatment. More specifically, eating a Mediterranean diet high in cruciferous vegetables can positively impact IBD patients.

Cruciferous vegetables have a protective effect against IBD. According to a 2023 study, early exposure to a diet of 10% raw broccoli sprouts causes several positive effects in a mouse model of chemically-induced IBD. This diet protected against common IBD symptoms including weight loss, diarrhea, and fecal bleeding. The protective effects were thought to be mediated by an anti-inflammatory compound called sulforaphane and increased diversity of gut bacteria.  

Concerningly, cruciferous vegetables were previously recommended to be reduced in the diets of IBD patients, which speaks to the lack of evidence-based dietary recommendations in the past. As simple as it seems, eating a diet higher in cruciferous vegetables shows promise as a feasible management strategy for IBD symptoms.  

From a more holistic point of view, a Mediterranean diet has been shown by a growing body of scientific evidence to have anti-inflammatory effects, which are extremely beneficial in the setting of IBD. Several recent studies have indicated that a Mediterranean diet high in fruits, vegetables, nuts, seeds, and legumes can cause significant reduction of symptoms or even complete remission in IBD patients. Decreased disease activity and relapses were also seen in patients on a Mediterranean diet. These results suggest a powerful role of dietary methods in management and prevention of IBD. 

Summary

IBD, which encompasses Crohn’s disease and ulcerative colitis, is a debilitating chronic inflammatory disease of the GI tract. Genetics, smoking, and bacterial exposures can meditate IBD risk. However, the effect of diet on this disease is a powerful, yet understudied factor. A Western diet high in processed foods can cause a basal level of GI inflammation, damage the mucosal barrier, and lead to dysbiosis. 

On the other hand, diet can be an extremely powerful treatment method for IBD. Contrary to past recommendations, recent studies indicate that cruciferous vegetables have protective effects against IBD symptoms The Mediterranean diet has led to significant symptom reduction and even complete remission in IBD patients. These findings reveal the powerful role of dietary interventions in both the management and prevention of IBD, emphasizing the need for evidence-based dietary recommendations.