Crohn's Disease: A Nutrition and Natural-Health Reference
1. Definition and Overview
Crohn's disease (CD) is a chronic inflammatory bowel disease (IBD) that can affect any region of the gastrointestinal tract, characterized by remitting and relapsing symptoms such as fatigue, fever, abdominal pain, diarrhea, and weight loss that may lead to hospitalization. It was first described as regional ileitis by Crohn, Ginzburg, and Oppenheimer in a case series presented at the American Medical Association annual meeting in 1932.
Crohn's disease is a multifactorial condition influenced by genetic, infectious, immunological, environmental, and dietary factors. Along with ulcerative colitis (UC), it is commonly included in the collective term inflammatory bowel diseases (IBD). Inflammation associated with CD is characterized by a discontinuous, transmural pattern, and can affect any part of the gastrointestinal tract.
2. Anatomical Distribution and Pathological Features
Approximately 30% of Crohn's disease cases involve the small bowel, particularly the terminal ileum; another 20% involve only the colon; and 45% involve both the small bowel and colon. Inflammation begins in the intestinal submucosa but may extend through the entire intestinal wall. Chronic inflammation leads to ulceration and the formation of cobblestone-appearing granulomas. Patches of disease and inflammation throughout the small and large intestine create the characteristic skip lesions.
3. Pathophysiology
Pathogenesis results from the interactions of environmental factors, the immune system, susceptibility genes, and host microbiome changes, leading to disruption of the intestinal mucosa. Crohn's disease evolution is mediated by a complex alteration of the inflammatory response characterized by alterations of the innate immunity of the intestinal mucosa barrier together with a remodeling of the extracellular matrix through the expression of metalloproteins and increased adhesion molecules expression. This reshaped microenvironment enhances leucocyte migration in the sites of inflammation, promoting a TH1 response through the production of cytokines such as IL-12 and TNF-Ξ±.
Crohn's disease is thought to be an overly aggressive response to normal flora bacteria by the body's immune system, specifically Th1 cytokines, in individuals with CARD15/NOD2 gene mutations. These cytokines elicit a pro-inflammatory response and perpetuate an autoimmune response resulting in further injury and inflammation.
Genetic Susceptibility
When the genetics of Crohn's disease were first investigated, a strong association was found with chromosome 16 (IBD1 gene), which led to the identification of three single nucleotide polymorphisms (SNPs) in the NOD2 gene (now called CARD15), the first gene clearly identified as a susceptibility gene. NOD2/CARD15 is a polymorphic gene involved in the innate immune system. Of its more than 60 variations, three play a role in 27% of patients with Crohn's disease, primarily in those with ileal disease.
Among immune-related conditions, CD is notable in that the genetic contribution to disease is high, with concordance rates up to 50% among monozygotic twins. More than 100 genetic markers have been associated with Crohn's disease, highlighting the polygenic nature of the disease.
4. Body Systems Involved
Gastrointestinal Tract (Primary Site)
Inflammation associated with CD is characterized by a discontinuous, transmural pattern and can affect any part of the gastrointestinal tract. Common gastrointestinal manifestations include abdominal pain, chronic diarrhea, rectal bleeding, and the formation of fistulae, strictures, and abscesses.
Extraintestinal Manifestations
Although Crohn's disease is a chronic inflammatory disease of the gastrointestinal tract, it can affect multiple organs behaving like a multisystem immune-mediated disease. The dysregulated immune system in patients with Crohn's disease leads to uncontrolled inflammation which primarily affects the gastrointestinal tract but may also affect various extraintestinal organs. Between 25β40% of IBD patients experience extraintestinal manifestations (EIMs), commonly in the joints, skin, bones, eyes, kidneys, and liver.
Some of these extraintestinal manifestations are due to systemic inflammation, some are due to malabsorption of nutrients and bile salts, and some are due to medications given for the treatment of Crohn's disease.
- Musculoskeletal: Affecting as many as 30% of patients with Crohn's, arthritis or inflammation of the joints is the most common extraintestinal complication of IBD. Although arthritis is typically associated with older age, in IBD it often strikes younger patients as well. As many as 30% to 60% of IBD patients have lower-than-average bone density, manifesting as osteoporosis, osteopenia, or osteomalacia. Prolonged use of corticosteroids, active inflammation, or vitamin D deficiency may contribute to these conditions.
- Skin: Approximately 40% of patients experience at least one extraintestinal manifestation of the condition; the skin is the most common site. Specific cutaneous manifestations include erythema nodosum and pyoderma gangrenosum.
- Eyes: The eye is the third major tissue type predisposed to immune-mediated EIMs. Nearly 2β7% of patients with IBD experience ocular manifestations. Episcleritis, scleritis, and anterior uveitis are the most common ocular EIMs.
- Hepatobiliary System: Approximately 0.96% of people with Crohn's disease have primary sclerosing cholangitis. Liver involvement of Crohn's disease can include cirrhosis and steatosis. About one in three people with Crohn's develop gallstones. Several factors linked with Crohn's can make gallstones more likely β for example, removal of the end of the small intestine or severe inflammation in this area, which can lead to poor absorption of bile salts.
- Pulmonary: There is a wide array of lung manifestations, ranging from subclinical alterations, airway diseases, and lung parenchymal diseases to pleural diseases. The most frequent manifestation is bronchial inflammation and suppuration with or without bronchiectasis.
- Neurological: Crohn's disease can cause neurological complications; the most common of these are seizures, stroke, myopathy, peripheral neuropathy, headache, and depression. Neurologic deficits may also arise from vitamin deficiencies, manifesting as diminished sensation, muscle atrophy, or gait abnormalities.
- Hematological: Crohn's disease may also involve the blood, resulting in manifestations such as increased risk of blood clots, deep venous thrombosis, and autoimmune hemolytic anemia. It may also cause anemia with associated symptoms of fatigue and a pale appearance.
5. Contributing and Associated Factors
Genetic Factors
Crohn's disease is a complex and multifactorial disease that is influenced by a combination of genetic and environmental factors. While genetic factors play a key role in the development of the disease, environmental factors also play a significant role in influencing risk. Implicated genes suggest that immunoreactivity to gut bacteria is a critical component in the risk of developing Crohn's disease. Interactions between genes and environment may facilitate the pathogenesis of Crohn's disease via damage to the lining of the intestine or perturbation of immune defenses, increasing exposure of the primed immune system to intestinal bacteria.
Environmental Factors
Environmental risk factors include childhood hygiene, air pollution, breastfeeding, smoking, diet, stress, exercise, seasonal variation, and appendectomy.
Smoking
Smoking is a well-described environmental risk factor for both the development of Crohn's disease as well as many adverse disease outcomes. Cigarette smoking changes the composition of the gut microbiome and also modifies the immune system response. Exposure to chronic smoke can change the integrity of the lining of the gut, making people susceptible to inflammation in the intestine. People with Crohn's disease who are current smokers have a worse outlook than those who do not smoke, with an increased need for surgeries and an increased need for immunosuppressants and corticosteroids.
Gut Microbiome and Dysbiosis
Diets rich in fibers, polyphenols, and prebiotics can promote the growth of anti-inflammatory microbial communities, while diets high in fat and protein but low in fiber can lead to dysbiosis, creating an environment that favors the expansion of pro-inflammatory microbes. This Western or Westernized dietary pattern has in recent decades spread from high- to low-income countries, and alongside this, the incidence of inflammatory diseases in these regions has risen. Continuous consumption of a Westernized diet alters enteric microbiota and disrupts the epithelial barrier, initiating low-grade inflammation.
A greater reduction in butyrate producers such as F. prausnitzii and increased abundance of E. coli is seen in ileal CD as compared to colonic CD, suggesting that there might be a stronger link between diet, microbiome, and CD phenotype.
Diet as a Risk Factor
Emerging evidence implicates Westernized dietary patterns, characterized by high intakes of ultra-processed foods, saturated fats, and low fiber, as contributing to intestinal dysbiosis, barrier dysfunction, and inflammation in genetically susceptible individuals. A high dietary intake of fiber has been reported to reduce the risk of CD by 40%. Studies including the Healthy Lifestyle in Europe by Nutrition in Adolescence Study and the prospective cohorts of the Nurses' Health Study (NHS) and NHS II have shown that a higher intake of fiber, specifically cruciferous vegetables and cereals, is associated with lower incidence of CD.
Vitamin D Status
Understanding the interplay between genetic and environmental factors is emphasized by the role of nucleotide-binding oligomerization domain-2, smoking, and vitamin D in the development of CD. Disease activity is linked to vitamin D insufficiency; vitamin D insufficiency was frequently associated with active disease status in CD patients.
6. Nutritional Deficiencies Associated with Crohn's Disease
Malnutrition is common in inflammatory bowel disease, especially in Crohn's disease, with studies indicating that it affects 20β85% of people with IBD. Due to malabsorption secondary to gastrointestinal insufficiency, chronic diarrhea, and the therapy used, there are different nutrient deficiencies including iron, magnesium, zinc, and selenium, as well as vitamins (vitamin D, folic acid, vitamin B12) in IBD patients.
Adults with Crohn's disease may be at risk of micronutrient insufficiency in clinical remission through restrictive eating, malabsorption, abnormal losses, or inflammation. The prevalence studies are consistent in reporting individuals with low vitamins A, B6, B12, and C, Ξ²-carotene, D, magnesium, selenium, and zinc.
Iron
Rectal bleeding can occur due to ulcers in the intestines, and can lead to iron deficiency and anemia. Iron deficiency is among the most common nutritional complications of CD, arising both from chronic blood loss and impaired absorption in inflamed intestinal tissue.
Vitamin B12
CD patients following ileocecal resections are particularly vulnerable to vitamin B12 deficiency due to absorption of vitamin B12 within the distal ileum. Lower concentrations of vitamin B12 are reported in CD patients, whereas similar concentrations are noted in UC patients and controls. Supplementation with vitamin B12 in CD patients following ileocecal resection should therefore be considered.
Folate
Sulfasalazine, as a folic acid antagonist, may lead to folate deficiency and anemia in patients being treated for IBD. A deficiency can also occur when taking Crohn's medications such as methotrexate, because both can block the absorption of this essential nutrient.
Zinc
Zinc supports cell growth, the building of proteins, and the immune system. A deficiency can occur due to severe diarrhea, extensive disease in the small intestine, and short bowel syndrome.
Vitamin D
Micronutrient blood concentrations tend to be negatively correlated with disease activity scores; this was a consistent finding in the studies of vitamin D, folate, and Ξ²-carotene. Vitamin D's unique link to inflammation suggests its role as both a biomarker and a pathophysiological mediator in CD.
7. Nutrients Studied in Relation to Crohn's Disease
Omega-3 Fatty Acids (Fish Oil / n-3 PUFAs)
Scientific Evidence: Long-chain omega-3 polyunsaturated fatty acids (n-3 PUFA) and vitamin D are associated with immune regulatory functions. However, the clinical evidence for omega-3 in CD is not supportive of benefit. Evidence from two large high-quality studies suggests that omega-3 fatty acids are probably ineffective for maintenance of remission in CD. Omega-3 fatty acids appear to be safe, although they may cause diarrhea and upper gastrointestinal tract symptoms. This conclusion was reached in a Cochrane systematic review (Lev-Tzion et al., 2014, Cochrane Database of Systematic Reviews), which assessed randomized placebo-controlled trials of n-3 for maintenance of remission in CD.
n-3 PUFAs may be beneficial in UC; however, n-3 PUFA lacks efficacy in Crohn's disease based on current evidence. Based on the results from randomized trials with CD populations, no strong conclusions can be made on the supplement's effect on inflammation due to insufficient statistical power. Further research is needed to clarify this.
Evidence strength: Negative to neutral for CD remission maintenance; two large high-quality RCTs found no benefit.
Probiotics
Scientific Evidence: Probiotics are not effective for Crohn's disease, but certain strains have demonstrated efficacy in UC and pouchitis. While some studies suggest potential benefits from the probiotic yeast Saccharomyces boulardii, others indicate that common probiotics like Lactobacillus may not offer significant improvement.
Evidence strength: Current evidence does not support probiotic use for CD remission induction or maintenance. The evidence is more favorable for UC and pouchitis.
Fiber and Prebiotics
The use of prebiotics and a low-inflammatory diet could be promising as therapeutic agents to restore a defective mucosal barrier and reduce intestinal permeability, either directly and/or by restoring gut dysbiosis. In a survey-based IBD cohort, Crohn's patients who avoided high-fiber foods were nearly 60% more likely to enter symptomatic flare during the ensuing six months than those who continued to eat fiber liberally.
Evidence strength: Epidemiological data are consistent but clinical trial evidence for fiber or prebiotic supplementation specifically in CD is preliminary.
8. Herbs and Natural Ingredients Studied in Relation to Crohn's Disease
Curcumin (Curcuma longa)
Traditional Use: Curcumin is used in different parts of the world for managing IBD. It is commonly consumed as a dietary supplement or included in traditional remedies in various cultures. In Ayurvedic and traditional South Asian medicine, turmeric has been used for centuries as an anti-inflammatory agent for digestive conditions.
Scientific Evidence: Some patients with Crohn's disease and ulcerative colitis are refractory to conventional therapies, and Curcuma longa derivatives have been considered as adjuvants. Owing to the anti-inflammatory and antioxidant effects, some clinical trials have used this plant in the therapeutic approach of IBD.
Some have suggested curcumin as promising for Crohn's disease; however, studies have produced mixed results, and some studies have shown curcumin to have no effect on Crohn's disease. A systematic review of existing literature found 13 placebo-controlled studies on curcumin treatment, which showed the treatment was useful for ulcerative colitis but showed no superiority over placebo for Crohn's disease. A different review suggested curcumin had the potential to be a safe and effective treatment. More studies are needed to draw a definitive conclusion.
Evidence strength: Moderate for UC (adjunctive remission maintenance); weak/mixed specifically for CD. Evidence to date does not confirm superiority over placebo in CD.
Wormwood (Artemisia absinthium)
Traditional Use: The use of Artemisia absinthium, or wormwood, dates back to the Ebers Papyrus, the oldest preserved medical document. Wormwood is referenced several times in the Bible and in the Historia Naturalis by Roman scholar Pliny the Elder. It was used as an anthelmintic by the ancient Egyptians, and by Hippocrates for rheumatism and menstrual pain. In the Middle Ages, wormwood was used as a purge and vermifuge and developed toward a "general remedy for all diseases."
Scientific Evidence: In a controlled trial, 10 randomly selected patients suffering from CD were given, in addition to their basic CD therapy, 3Γ750 mg dried powdered wormwood for 6 weeks. Ten patients who met the inclusion criteria served as a control group. A minimum score of 200 on the Crohn's Disease Activity Index (CDAI) was required at baseline for inclusion in each group.
At 6 weeks, 8 of 10 (80%) patients on wormwood and 2 of 10 patients (20%) on placebo achieved clinical remission defined as a CDAI below 170 or a reduction in CDAI by 70 points. Clinical trials showed that wormwood administration promoted clinical improvement of symptoms in all patients, whereas no amelioration in disease was observed in the placebo group. The beneficial effect was associated with a significant decrease in TNF-Ξ± serum levels compared with the placebo group. Suppression of TNF-Ξ±, as well as other pro-inflammatory cytokines like IL-1Ξ² and IL-6, by wormwood extracts has been reported in vitro.
There is limited data suggesting wormwood may be beneficial in Crohn's disease.
Evidence strength: Preliminary. Results from small controlled trials are encouraging, but the number of studies and patient populations are insufficient to draw definitive conclusions. Further large RCTs are needed.
Boswellia serrata (Indian Frankincense)
Traditional Use: The oleo-gum resin from Boswellia serrata (Burseraceae), or Indian frankincense, is a traditional Ayurvedic remedy used to treat inflammatory diseases. Boswellia serrata, known in India as salai guggal, is a staple of Ayurvedic medicine referenced in texts such as the Charaka Samhita from the first to second century AD and the Astangahrdaya Samhita from the seventh century.
Scientific Evidence: One randomized, double-blind, placebo-controlled trial of patients with active Crohn's disease compared 3.6 grams per day of Boswellia serrata extract H15 to mesalazine. Both interventions elicited significant decreases in Crohn's Disease Activity Index (CDAI), and statistical analyses concluded that boswellia had equivalent efficacy to mesalazine. Out of 83 patients with Crohn's disease β 44 treated with H15 and 39 treated with mesalazine β the CDAI was reduced by 90 scores with H15 and by 53 scores with mesalazine, on average.
According to a survey performed in Germany, approximately 36% of IBD patients have been administered Boswellia serrata extracts to treat their intestinal condition, reporting positive therapeutic effects.
Evidence strength: Preliminary to moderate. A small number of clinical trials suggest equivalence or benefit compared to mesalazine in active CD. The evidence base is limited in size and requires replication in larger studies.
Mastic Gum (Pistacia lentiscus)
Traditional Use: Mastic gum, a resin obtained from the mastic tree native to the Greek island of Chios, has been used in traditional medicine across the Eastern Mediterranean for gastrointestinal complaints for thousands of years.
Scientific Evidence: In Crohn's disease, mastic gum was superior to placebo in inducing remission in clinical trials. The most important clinical trials conducted so far in IBD refer to the use of mastic gum, tormentil extracts, wormwood herb, aloe vera, germinated barley foodstuff, and boswellia serrata.
Evidence strength: Preliminary. Positive signal from small RCTs but evidence base remains limited.
Aloe Vera (Aloe barbadensis)
Traditional Use: Aloe vera represents a quite popular folk remedy for inflammatory conditions. Its use for gastrointestinal complaints spans many traditional healing systems in Africa, the Middle East, and the Americas.
Scientific Evidence: Clinical evidence for aloe vera has been predominantly studied in ulcerative colitis rather than Crohn's disease. In ulcerative colitis, aloe vera gel was superior to placebo in inducing remission or clinical response. There is limited data that suggests wormwood may be beneficial in Crohn's disease, and that aloe vera may improve clinical outcomes in UC.
Evidence strength: Insufficient for CD specifically. Most RCT evidence pertains to UC. No adequate clinical trials in CD have been identified in the reviewed literature.
Tripterygium wilfordii (Thunder God Vine)
Traditional Use: Tripterygium wilfordii has been used in traditional Chinese medicine for centuries for inflammatory and autoimmune conditions.
Scientific Evidence: In Crohn's disease, Tripterygium wilfordii was superior to placebo in preventing clinical postoperative recurrence in clinical trials reviewed in the IBD herbal therapy literature. The evidence base for this herb in CD is, however, very limited, and significant safety concerns regarding its toxicity profile have been noted in the broader medical literature.
Evidence strength: Very preliminary. Very few trials exist. Significant toxicity concerns mean this herb requires careful appraisal before use.
9. Dietary Factors and Patterns in Crohn's Disease
Western Dietary Pattern β Risk
The nutritional patterns and habits of developed Western countries, including high intake of red meat, refined carbohydrates, ultra-processed and industrialized foods, high total fat and especially saturated fat, and low quantities of vegetables, fruit, and legumes, have been associated with increased mucosal inflammation and decreased amounts of bacteria involved in fiber degradation. Genetics, lifestyle, and a "Western" diet (high in fats, sugar, and protein but low in fiber) are all proposed to play a role in inducing dysbiosis in CD.
Mediterranean Diet β Potential Protection
Mediterranean-oriented diets seem to provide an inverse association with the incidence of CD. The Mediterranean Diet (MD) emphasizes the consumption of whole grains, seeds, nuts, legumes, vegetables, and fruits, followed by a moderate consumption of fish, poultry, and dairy products. It focuses on extra virgin olive oil as the principal source of fat, while processed red meat products and sugars should be kept low.
In the IBD population, there may be a role for the Mediterranean diet due to its anti-inflammatory effects, long-term sustainability, and role in improving cardiovascular health. A healthy lifestyle based on the Mediterranean Diet, accompanied by sufficient physical activity and adequate sleep and rest, and combined with successful management of stress and anxiety, is associated with lower levels of inflammatory markers such as CRP, calprotectin, TNFΞ±, IL-17, IL-12, and IL-13.
Exclusive Enteral Nutrition (EEN)
Exclusive enteral nutrition (EEN) entails 6β8 weeks of liquid meal replacement with the exclusion of all other food and is a first-line therapy for mild to moderate CD. Nutritional therapies, including exclusive enteral nutrition (EEN) and the Crohn's Disease Exclusion Diet (CDED), have shown efficacy in inducing and maintaining remission, particularly in pediatric populations.
Crohn's Disease Exclusion Diet (CDED)
In active Crohn's disease, the use of exclusive enteral nutrition, the Crohn's disease exclusion diet, or the specific carbohydrate diet may be used as a short-term adjunct to medical therapy and may improve mucosal healing. The CDED is a structured, whole-food diet designed to reduce exposure to dietary components hypothesized to negatively affect the microbiome and intestinal barrier.
Low-FODMAP Diet
Highly fermentable short-chain carbohydrates can aggravate gas and pain even when inflammation is quiescent. A 2023 systematic review of randomized trials concluded that a low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) strategy reduced abdominal pain scores in CD. The low-FODMAP diet can assist in reducing symptoms for patients without evidence of active bowel inflammation.
Dietary Fiber
In a survey-based IBD cohort, Crohn's patients who avoided high-fiber foods were nearly 60% more likely to enter symptomatic flare during the ensuing six months than those who continued to eat fiber liberally. However, tolerance to dietary fiber depends on disease location, activity, and individual patient characteristics, and fiber from certain sources may not be appropriate during active flares with intestinal narrowing.
Specific Dietary Components
Consumption of specific foods and drinks, such as spicy and fatty foods, raw vegetables and fruits, dairy products, carbonated beverages, and coffee or tea, can provoke the exacerbation of CD symptoms in susceptible individuals, although these associations are largely self-reported and highly individualized.
10. Lifestyle Factors
Physical Activity
Environmental risk factors for CD include, among others, exercise and stress. Physical activity has been discussed in the literature as a potentially modifiable factor; population-based and epidemiological studies have associated sedentary behavior with increased IBD risk, though the mechanistic evidence is still being established.
Stress
Several environmental risk factors have been identified for CD, including smoking, diet, and stress. An interaction between genetic susceptibility and unhealthy lifestyle factors like smoking, alcohol consumption, low physical activity, and unbalanced nutritional habits has been reported in CD onset literature.
Breastfeeding
The pathogenesis of Crohn's disease involves host, genetic, and environmental factors. These factors result in disturbances in the innate and adaptive immune systems and composition of the intestinal microbiota. Breastfeeding has been identified in epidemiological research as a potentially protective environmental factor, possibly through its influence on early gut microbiome establishment.
Hygiene Hypothesis
In countries that have adopted a "modernized" lifestyle, the incidence rates of IBD have steeply increased in the last few decades. This observation forms part of the "hygiene hypothesis" β the idea that reduced microbial exposure in early life may alter immune development in ways that predispose to inflammatory conditions like CD.
References
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