"Trust your mechanic, [and] he'll [...] rip you off." Jello Biafra
Problem
What is Crohn's disease?
Crohn's disease is a chronic (long-term) inflammatory bowel disorder and can get worse ("progressive" disease). Crohn's can affect any part(s) of the gastrointestinal tract, from the mouth to the anus [Popa et al. 2020].
What happened so far ...
Your family doctor (general practitioner) will usually refer you to a gastroeneterologist, who might tell you (incorrectly) that diet has nothing to do with Crohn's disease, that you will need medication for life (and increasingly more medication), and that at some point sooner or later you will need to have part of your intestine cut out, maybe requiring an artificial exit that is not your anus.
Medical doctors are often right, and often they're wrong. Usually they are tactless (correct me if I'm wrong), often have delusions of grandeur (I'd be interested to know why), couldn't tell you the difference between "ethnic" and "ethics", and to put it mildly they have a conflict of interest (they love and/or need money - to pay staff, rent, expensive equipment, trips to the Maldives, housemaids, etc.).
Hope in a hopeless world
Your job now is to prove your doctor wrong, which isn't exactly unheard of. It has been done many times. If bad diet and stress are main causal factors, then healthy diet and relaxation may work wonders.
What is the true cause of Crohn's disease?
No one knows exactly. The easy answer (you might hear) is that it is an "idiopathic" disease, i.e., the cause is unknown.But probably the cause is a mix of genetic predisposition (susceptibility) and environmental factors, which can (quite likley do) include diet, other lifestyle factors (including smoking), and environmental pollution but also, importantly, psychological stress.
"Interestingly, in mild to moderate pediatric CD [Corhn's disease], sustained diet-induced remission [symptom improvement] by both CDED [Crohn’s disease exclusion diet ] + PEN [partial enteral nutrition] and EEN [exclusive enteral nutrition] is associated with a marked decrease in fecal kynurenine levels. Importantly, in samples from patients failing to sustain remission, no changes were observed. The reduction in specific kynurenine pathway compounds and the increase in serotonin pathway compounds are associated with diet-induced and sustained remission." [Boneh et al. 2023]
Potential causal mechanisms
"Inflammation is a potential mechanism through which diet modulates the onset of inflammatory bowel disease." [Lo et al. 2020]
Dietary factors that might contribute to getting Crohn's disease
"[...] We collected data from 166,903 women and 41,931 men in the Nurses' Health Study (1984-2014), Nurses' Health Study II (1991-2015), and Health Professionals Follow-up Study (1986-2012). Empirical dietary inflammatory pattern (EDIP) scores were calculated based on the weighted sums of 18 food groups [...] [To be honest, this 18 food group score that the EDIP is based on is quite sketchy, but generally it says vegetables, fruit, tea, and coffee are anti-inflammatory, and meat (and fish, they say!), white flour products, sweets, etc. are pro-inflammatory - I would rather go by this list of "good and bad" foods (Satija et al. 2017)].
The median age at IBD [irritable bowel disease] diagnosis was 55 years (range 29-85 years). Compared with participants in the lowest quartile of cumulative average EDIP score, those in the highest quartile (highest dietary inflammatory potential) had a 51% higher risk of CD [Crohn'sdisease] (HR 1.51; 95% CI 1.10-2.07; Ptrend = .01). [...]
Conclusions: In an analysis of 3 large prospective cohorts, we found dietary patterns with high inflammatory potential to be associated with increased risk of CD [...]." [Lo et al. 2020 [from the Harvard School of Public Health]
The intestinal microbiome
"Microbiome investigations have shown that reduction in Proteobacteria [healthy plant-based diets - again, see the list by Satija et al. 2017 - are associated with such a reduction (Simpson & Campbell 2015)] is associated with remission [symptom improvement] (and that nonresponders do not display this drop in Proteobacteria). It is important to note that microbiome changes are not fully corrected, even when clinical remission is achieved at 6 weeks. Exclusive enteral nutrition [liquid formula diet] patients who resume a normal diet tend to lose some of the gains in dysbiosis correction (notably Proteobacteria increase), as Escherichia coli continues to be more abundant, even when sustained remission is achieved." [Boneh et al. 2023]
"Recently, the effect of CDED + PEN on fecal calprotectin (FCP; marker of mucosal inflammation) was retrospectively investigated in a group of 48 children with active CD and increased FCP levels (>250 µg/g), showing that a 12-week course of CDED + PEN treatment led to a significant decrease in FCP in the studied group and to normalization of this parameter in every third patient. Thirty-five percent of patients normalized FCP and 56.2% showed a 50% reduction of its values. All patients with normal FCP at week 12 were in clinical remission, and 94% of them had also normal CRP [commonly measured inflammatory marker in the blood] levels." [Boneh et al. 2023]
Non-dietary lifestyle aspects
Smoking seems to increase the risk of Crohn's disease [Carreras-Torres 2020].
Solution
Is medication (and surgery) necessary?
"Ultimately, most patients will require drug therapy; long-term dietary monotherapy can be considered in highly motivated patient[s], with close follow-up; drug and diet should usually be combined in less motivated patients.[...]
CDED [Crohn’s disease exclusion diet ] has demonstrated its highest effectiveness in mild to moderate, uncomplicated, pediatric, luminal CD [Crohn's disease] patients with a relatively short disease duration (ideally treatment-naïve), with active inflammation and generally ileal or ileocolonic disease; more recent studies support similar indications in adult patients, as detailed previously. However, it is not clear whether CDED is beneficial for the therapy of severe and extensive disease, penetrating disease [with holes in the intestinal wall], perianal fistulae, and for extraintestinal manifestations, and whether it can be suggested to patients with strictures.
[...]
Though further studies are needed, induction or reinduction of remission with CDED as an adjunct to pharmacologic therapy has many potential advantages including reducing exposure to further drugs while targeting the environmental mechanism of disease without additional toxicity, which could be especially important for children and adolescents with decades of life with the disease ahead [in adults, the assumption is that the drugs will only kill you at such a late date that you will be dead by then anyway].
Though further studies are needed, induction or reinduction of remission with CDED as an adjunct to pharmacologic therapy has many potential advantages including reducing exposure to further drugs while targeting the environmental mechanism of disease without additional toxicity, which could be especially important for children and adolescents with decades of life with the disease ahead [in adults, the assumption is that the drugs will only kill you at such a late date that you will be dead by then anyway].
[...]
[...] the judicious use of EEN [exclusive enteral nutrition, i.e., liquid formula diet only] can provide real benefit in terms of improving perioperative outcomes and avoiding surgery in some patients." [Boneh et al. 2023]
[...] the judicious use of EEN [exclusive enteral nutrition, i.e., liquid formula diet only] can provide real benefit in terms of improving perioperative outcomes and avoiding surgery in some patients." [Boneh et al. 2023]
More info regarding medication below.
What should you eat if you have Crohn's disease?
Unfortunately, there are no easy answers. Fortunately, however, the answer is not that difficult. Generally speaking, a healthy dietary pattern is the same, more or less, for everyone and for the prevention as well as treatment of Crohn's disease and pretty much any other disease too (heart disease, cancer, diabetes, ... you name it). Again, see the list of healthy plant foods by Satija et al. 2017 and focus mostly on these. Some people with Crohn's disease are sensitive to very specific foods, e.g., nightshades such as tomatoes and aubergines (eggplants) or to high-FODMAP foods (see below).
[...] One proposed mechanism for how diet contributes to the development of CD is through the individual components of a “Western diet” (animal fat, sugar, wheat proteins, emulsifiers, maltodextrin, low-fiber) [...].
[...] A significant component of the Western diet thought to play a role in CD risk is animal protein. The most significant study supporting this hypothesis utilized a prospective cohort of women in France aged 40–65 enrolled in the Etude ÉpidÉmiologique des femmes de la Mutuelle GÉnÉrale de l’Education Nationale (E3N) study. In this population, higher total protein intake, specifically animal protein from meat or fish, was associated with increased risk of IBD (HR 3.03, 95% CI 1.45–6.34) [19]. However, a relationship between dietary protein and CD risk has not been demonstrated in subsequent studies in other populations [...]." [Goens & Micic 2020]
"Dietary therapy is increasingly recognized for the management of Crohn's disease (CD) over recent years [...]." [Boneh et al. 2023]
[...] elemental diets (Flexical, Elemental 028), semi-elemental diets (Pregomin), polymeric diets (Modulen IBD), whole protein based formulas, and ω-3 fatty acid supplementation were found. Data indicated that diet therapies were equal to or more effective than corticosteroid therapies when used to treat Crohn's disease. Regrettably, we could not identify controlled studies investigating complementary, alternative and integrative medicine approaches. Our review provides an updated overview of controlled studies investigating dietary therapies used in the treatment of pediatric Crohn's disease, and demonstrates that the current study situation does not reflect the actual use of complementary, alternative and integrative therapies. Therefore, clinical trials are necessary to estimate risks and benefits of such therapies. The review indicated that enteral diets and ω-3 [omega-3, see point 5 here] fatty acid supplementation may be an effective alternative to corticosteroid treatments for children with Chron's disease." [Schwermer et al. 2020]
Eat more plant protein ... and whole foods
"[...] According to recent ESPEN guidelines, adults patients are required to consume 1.2 to 1.5 g/kg of protein [i.e., for example 105 g of protein dor a 70 kg (1.5 x 70 = 105) person] during active disease [i.e., when symptoms are bad] and 1 g/kg during remission [i.e., when symptoms improve]. This amount could be met by addition of formula, concentrating the formula up to 1.5 Kcal/mL, addition of egg whites, and consumption of fish when patients agree, up to 2 to 3 times per week until the desired intake is met. In vegans, there are fewer options [tofu, tempeh, plain soya milk, plain soya yoghurt, soya/pea protein powder, blended legumes (e.g., hummus, lentil soup)] available, and closer monitoring is imperative. Patients who are willing to follow CDED should be aware that several compromises need to be made to meet the requirements; a plant-based protein formula could be used. Achieving the requirements with whole foods rather than protein supplementation is preferred, as many supplements contain additives [vegan protein powders often have artificial sweeteners, which may or may not be an issue]. Consumption of legumes during active disease could be challenging due to the potential symptoms these might cause [it's a common misconception that eating legumes per se causes bloating and flatulence, but this is not the case if you get used to these foods and especially with blended foods or small legumes (e.g., lentil soup, red lentils, hummus, small brown lentils, 100% peanut butter, etc.) or tofu, soya milk, soya yoghurt, etc. as well as nut butters and seed butters (e.g., tahini). There's also sunflower protein (like soya mince)]; this is why legumes are integrated into phase 2 after clinical improvement is achieved. In some anecdotal cases, where patients are used to consuming these foods [legumes], the dietitian could use legumes as a protein source or recommend a texture modification such as a homemade orange lentil paste or hummus. Additional protein sources could include a free additive protein enriched yogurt, according to the dietitian discretion. Adjustments for allergies are based on the dietitians’ guidance to meet the protein requirements, as described previously.
[...]
we now prefer the term recommended foods, not mandatory. Chicken breast and eggs were chosen to guarantee enough protein; however, if the patient will not eat eggs or chicken, the dietitian can provide alternatives and solutions as mentioned previously. The same applies to potatoes, bananas, and apples. These foods are recommended to increase consumption of resistant starch in order to produce more SCFAs [short-chain fatty acids, produced by intestinal bacteria when fibre-rich foods, i.e., whole plant foods, are eaten] and pectin [many fruits as well as beans, carrots, sweet potatoes, and potatoes are rich in pectin]. In cases where patients cannot tolerate these food items or do not want to consume them, the dietitian should provide substitutes using different fruits and vegetables based on the patient’s personalized tolerance and reduce the pressure from the concept of mandatory foods.
Regarding fruits and vegetables, the dietitian should guide the patients based on their individual tolerance to fiber." [Boneh et al. 2023]
Try a low-FODMAP diet
The best list of vegan low-FODMAP foods is this one (alternative link), made by Virginia Messina, RD.
Low-fermentable oligo-, di-, mono-saccharides and polyols (FODMAP) diet (LFD):
"The majority of the studies included in this review show the significant efficiency of the LFD in CD [Crohn's disease] patients. We found significant evidence demonstrating that the LFD has a favorable impact on gastrointestinal symptoms in CD patients. Notwithstanding the evidence, it remains to be established if an LFD is more efficient than other types of diets in the short term and especially in the long term." [Popa et al. 2020]
Everyone should follow a fibre-rich diet anyway:
"A systematic review with a meta-analysis was carried out to determine the efficacy of a diet rich in fiber with or without cointervention to improve remission rates for CD [Crohn's disease].
[...] Consumption of fiber in the diet could improve remission rates for CD patients who receive or do not receive other treatment [i.e., medication] to maintain remission." [Serrano Fernandez et al. 2023]
"Higher intake of dietary fiber (fruit fiber) has been associated with a reduced risk for CD." [Goens & Micic 2020]
Several small studies have noted a reduction in CD-severity scores [36,37,38] and inflammatory markers [1, 39, 40] with implementation of the SCD in pediatric populations. Suskind et al. conducted a prospective cohort study assessing the impact of the SCD in 12 pediatric patients with IBD (9 with CD). Participants were initiated on a SCD diet without alterations in medication use within 1–2 months prior to study entry. Mean pediatric Crohn’s disease activity index (PCDAI) scores for participants decreased from 28.1 ± 8.8 to 4.6 ± 10.3, and an elevated C-reactive protein (CRP) decreased from 70% of individuals at baseline to 20% of individuals after 12 weeks of dietary therapy. Changes in the fecal microbiome were also demonstrated with the SCD, although clear cause-and-effect changes were not demonstrated [38]. While improvements in mucosal healing have not been demonstrated with the SCD [40], further studies are awaited to assess the comparative effectiveness of the SCD in strict randomized studies (DINE-CD trial comparing SCD to Mediterranean diet in CD - NCT03058679)." [Goens & Micic 2020] ... Results from the "DINE-CD" study (USA) have now been published and found: "The SCD [specific carbohydrate diet] was not superior to the MD ["Mediterranean diet"] to achieve symptomatic remission, FC [faecal calprotectin, inflammatory marker in stool] response, and CRP [inflammatory marker in the blood] response. CRP response was uncommon. Given these results, the greater ease of following the MD and other health benefits associated with the MD, the MD may be preferred to the SCD for most patients with CD with mild to moderate symptoms." [Lewis et al. 2021]
Exclusive enteral nutrition (liquid diet formula only)
Liquid formula diets, made by pharmaceutical companies. There aren't any vegan ones, I think."The exclusive enteral nutrition (EEN) diet remains the most validated nutritional recommendation for inducing remission in CD [Crohn's disease]." [Goens & Micic 2020]
"[...] including the use of exclusive enteral nutrition (EEN) as first-line therapy for pediatric CD [Crohn's disease] according to current guidelines." [Boneh et al. 2023]
So-called "exclusion diets"
"Several new exclusion diets modeled after EEN [exclusive enteral nutrition] and SCD [specific carbohydrate diet] have shown potential efficacy in smaller studies that warrant replication." [Goens & Micic 2020]
"The Crohn's disease exclusion diet (CDED) is a whole-food diet designed to reduce exposure to dietary components that are potentially pro-inflammatory [in other words: choose a "whole food"-based, plant-based diet - again, see the list by Satija et al. 2017], mediated by negative effects on the gut microbiota, immune response, and the intestinal barrier. The CDED has emerged as a valid alternative to EEN with cumulative evidence, including randomized controlled trials, supporting use for induction of remission and possibly maintenance in children and adults.
[...]
We concluded that CDED is an established dietary therapy that could serve as an alternative to EEN in many pediatric and adult cases, especially with mild to moderate disease. In severe disease, complicated phenotypes, or with extraintestinal involvement, CDED should be considered on a case-by-case basis, according to physician and dietitians' discretion. More studies are warranted to assess the efficacy of CDED in different scenarios." [Boneh et al. 2023]
"Evidence on CDED among individuals with different types of dietary habits such as vegetarian, vegan, and allergies is scarce and is mostly based on practice and personal experience. The main concern with following a vegetarian and, even more so, a vegan version of CDED is ensuring enough protein and vitamins (eg, [vitamin] B12 [just take a supplement, see here - children: take half the amounts]), especially in children, to allow for normal growth. The CDED [that these authors came up with, for omnivores] contains recommended protein sources such as chicken breast and eggs. The role of dietitians in [helping] these [vegetarian and vegan Crohn's disease] patients is pivotal since dietitians should calculate and adjust the protein intake and allow for substitute alternatives to ensure sufficient consumption." [Boneh et al. 2023]
"Specific carbohydrate diet"
"The specific carbohydrate diet (SCD) has demonstrated reductions in CD severity scores in conjunction with medical therapies, and larger trials on its efficacy are ongoing. [...]
[...]
The Specific Carbohydrate Diet (SCD) restricts the use of complex carbohydrates and was initially developed in the 1920’s for the management of celiac disease [...]. Essentially grain[-]free and low in lactose and simple sugars, the SCD is hypothesized to be effective in CD due to its elimination of complex carbohydrates, processed foods, most dairy products, and common food additives such as the polysaccharide maltodextrin [based on observations in mouse experiments].
[My guess is that such a "specific carbohyrate diet" could be helpful because (1) it avoids sugary stuff, (2) it avoids gluten (by avoiding grains; and some people are sensitive to gluten), (3) it mostly avoids dairy (same as with gluten), (4) it has some aspects in common with low-FODMAP diets (see above).]
Several small studies have noted a reduction in CD-severity scores [36,37,38] and inflammatory markers [1, 39, 40] with implementation of the SCD in pediatric populations. Suskind et al. conducted a prospective cohort study assessing the impact of the SCD in 12 pediatric patients with IBD (9 with CD). Participants were initiated on a SCD diet without alterations in medication use within 1–2 months prior to study entry. Mean pediatric Crohn’s disease activity index (PCDAI) scores for participants decreased from 28.1 ± 8.8 to 4.6 ± 10.3, and an elevated C-reactive protein (CRP) decreased from 70% of individuals at baseline to 20% of individuals after 12 weeks of dietary therapy. Changes in the fecal microbiome were also demonstrated with the SCD, although clear cause-and-effect changes were not demonstrated [38]. While improvements in mucosal healing have not been demonstrated with the SCD [40], further studies are awaited to assess the comparative effectiveness of the SCD in strict randomized studies (DINE-CD trial comparing SCD to Mediterranean diet in CD - NCT03058679)." [Goens & Micic 2020] ... Results from the "DINE-CD" study (USA) have now been published and found: "The SCD [specific carbohydrate diet] was not superior to the MD ["Mediterranean diet"] to achieve symptomatic remission, FC [faecal calprotectin, inflammatory marker in stool] response, and CRP [inflammatory marker in the blood] response. CRP response was uncommon. Given these results, the greater ease of following the MD and other health benefits associated with the MD, the MD may be preferred to the SCD for most patients with CD with mild to moderate symptoms." [Lewis et al. 2021]
"Mediterranean diet" here refers to the "traditional Mediterranean diet", which is a bit of a fantasy creation. Basically, it is exactly what is recommended everywhere, a plant-based, whole food-based healthy diet - again, see the list by Satija et al. 2017. The traditional Mediterranean diet has particularly been "hyped" by researchers from Spain (maybe in part due to some nationalistic tendencies - Medi diet and corrida!). The traditional Mediterraean diet is based on vegetables, fruit, legumes, whole grains (allegedly), nuts, seeds, avocados, red wine, some fish, and - the only necessary ingredient (the "sine qua non" Miguel Ángel Martínez-González) of the traditional Mediterranean diet is olive oil. And clearly, no healthy diet requires olive oil.
It all boils down to a healthy plant-based, whole food-based diet
"In contrast to plateauing incidence in high-income countries, areas of the world with historically low rates, such as Asia or South America, seem to be witnessing an increase in incidence and prevalence, possibly due to changes in lifestyle, diet, and pollution exposure.
[...]
Dietary factors including ultra-processed foods have been associated with higher risk for developing Crohn's disease (hazard ratio 1.82, 95% CI 1.22–2.72 for five or more servings per day; moderate-high-quality evidence)."
[...]
Diet modification to treat Crohn's disease
In addition to potential effects on intestinal inflammation and symptoms, dietary therapies also enhance the nutritional status of patients with Crohn's disease. The benefit of dietary therapies is evident in the preoperative setting, in which treatment with exclusive enteral nutrition (EEN) shortens duration of surgery and reduces postoperative complications. EEN is used globally as an alternative to steroids [cortisone, etc.], especially in children, where it has a benefit over corticosteroids [steroids, medication] in improving mucosal inflammation. Although complying with a strict EEN diet is challenging, partial enteral nutrition (PEN) might only be needed. When used in combination with the Crohn's disease exclusion diet (CDED; a whole foods diet administered in phases attempting to limit foods that alter the microbiome or intestinal barrier), PEN plus CDED was superior to EEN alone in inducing clinical remission and normalising CRP compared with EEN alone after 12 weeks. CDED alone has been shown to have no differences in sustained or endoscopic remission 24 weeks after initiation combined to [I think, they mean compared to] CDED with PEN in an open-label, pilot, randomised trial of adults. The evidence for the simple carbohydrate [see above] and Mediterranean diets [see above] remains less clear." [Dolinger et al. 2024]
Dietary factors including ultra-processed foods have been associated with higher risk for developing Crohn's disease (hazard ratio 1.82, 95% CI 1.22–2.72 for five or more servings per day; moderate-high-quality evidence)."
[...]
Diet modification to treat Crohn's disease
In addition to potential effects on intestinal inflammation and symptoms, dietary therapies also enhance the nutritional status of patients with Crohn's disease. The benefit of dietary therapies is evident in the preoperative setting, in which treatment with exclusive enteral nutrition (EEN) shortens duration of surgery and reduces postoperative complications. EEN is used globally as an alternative to steroids [cortisone, etc.], especially in children, where it has a benefit over corticosteroids [steroids, medication] in improving mucosal inflammation. Although complying with a strict EEN diet is challenging, partial enteral nutrition (PEN) might only be needed. When used in combination with the Crohn's disease exclusion diet (CDED; a whole foods diet administered in phases attempting to limit foods that alter the microbiome or intestinal barrier), PEN plus CDED was superior to EEN alone in inducing clinical remission and normalising CRP compared with EEN alone after 12 weeks. CDED alone has been shown to have no differences in sustained or endoscopic remission 24 weeks after initiation combined to [I think, they mean compared to] CDED with PEN in an open-label, pilot, randomised trial of adults. The evidence for the simple carbohydrate [see above] and Mediterranean diets [see above] remains less clear." [Dolinger et al. 2024]
"Another clinically relevant finding was that 80% of patients in remission at week 6 maintained clinical remission at week 24 on dietary monotherapy [only diet, no medication], allowing more than 50% of patients in the ITT [intention-to-treat, all study participants] population to achieve sustained remission at 6 months. Dietary therapy was accompanied by a significant and progressive reduction in C-reactive protein and faecal calprotectin.
Mucosal healing is an important goal in Crohn’s disease, and to our knowledge this is the first study to demonstrate the ability of any dietary intervention to achieve endoscopic remission over an extended period of dietary therapy (35% of the ITT population had achieved endoscopic remission at 24 weeks). Previous studies of exclusive enteral nutrition (a non-sustainable diet in children) have included immunomodulators, thus this is also the first study to demonstrate that dietary therapy can achieve these goals in a prospective trial in adults without concurrent immunomodulators or steroids [medication].
[...]
[...]
Partial enteral nutrition provides nutritional security and ensures nutritional needs are met in patients
who might be malnourished. However, it can also be a barrier to dietary therapy in adults. We used a randomised study design to address the need for partial enteral nutrition in adults. ............... Dietary therapy has been postulated to reduce inflammation by altering the microbiome and reducing
intestinal permeability. The mechanism by which exclusive enteral nutrition works remains unclear.
Exposure to habitual diet [often a rather unhealthy diet] in addition to formula seems to negate or reduce the effects of exclusive enteral nutrition therapy. Moreover, once habitual diet is re-introduced
after a course of exclusive enteral nutrition, many patients have a rebound increase in inflammatory indices or experience flare within weeks of re-exposure to food. [...]" [Yanai et al. 2022]
who might be malnourished. However, it can also be a barrier to dietary therapy in adults. We used a randomised study design to address the need for partial enteral nutrition in adults. ............... Dietary therapy has been postulated to reduce inflammation by altering the microbiome and reducing
intestinal permeability. The mechanism by which exclusive enteral nutrition works remains unclear.
Exposure to habitual diet [often a rather unhealthy diet] in addition to formula seems to negate or reduce the effects of exclusive enteral nutrition therapy. Moreover, once habitual diet is re-introduced
after a course of exclusive enteral nutrition, many patients have a rebound increase in inflammatory indices or experience flare within weeks of re-exposure to food. [...]" [Yanai et al. 2022]
Conclusion
CDED plus PEN was better tolerated than EEN in children with mild to moderate CD. Both diets were effective in inducing remission by week 6. The combination CDED plus PEN induced sustained remission in a significantly higher proportion of patients than EEN, and produced changes in the fecal microbiome associated with remission. These data support use of CDED plus PEN to induce remission in children with CD." [Levine et al. 2019]
The German recommendations also consider a vegetarian diet suitable in the case of Crohn's disease, and state: "[English in the original:] In addition to the dietary recommendations of DGE [German Nutrition Society], a mediterranean-type of diet as well as a vegetarian diet are considered to be of equal health value. Depending on disease-specific requirements, complementary recommendations are given [...].
[...]
[Translation from German:] The protein requirement is increased due to the catabolic metabolic state in the context of inflammation and possible intestinal protein loss. Therefore, a protein intake of 1-1.5 g/kg body weight/day is recommended, or up to 2 g/kg body weight/day in septic or severely malnourished patients.
Isolated micronutrient deficiencies in chronic inflammatory bowel disease can be treated with supplements, if necessary parenterally. Particular attention should be paid to a deficiency in calcium, vitamin D, folate and vitamin B12, iron and zinc.] [...]" [Hauner et al. 2019]
Isolated micronutrient deficiencies in chronic inflammatory bowel disease can be treated with supplements, if necessary parenterally. Particular attention should be paid to a deficiency in calcium, vitamin D, folate and vitamin B12, iron and zinc.] [...]" [Hauner et al. 2019]
Blood and stool sample tests
"Initial laboratory findings might include abnormalities on the complete blood count, including leucocytosis, anaemia due to either chronic disease, or micro and macroscopic blood loss via the gastrointestinal tract, or both, and thrombocytosis, a surrogate marker of acute inflammation. Additional inflammatory markers, C-reactive protein (CRP), and erythrocyte sedimentation rate might be elevated. A CRP greater than or equal to 2.7 mg/dL [= 27 mg/L] has the highest diagnostic positive predictive value of 89.6%. However, many patients will have a normal CRP despite active gastrointestinal tract inflammation. Use of the stool biomarker faecal calprotectin less than 40 μg/g in the primary care setting can exclude diagnosis, with less than 1% of patients later diagnosed. Faecal calprotectin concentrations greater than or equal to 1000 mg/g result in a maximum predictive value of 78.7% for Crohn's disease activity, and concentrations less than 250 μg/g correlate with endoscopic remission in Crohn's disease, whereas two repeated values greater than 250 μg/g without symptoms indicate a greater than 50% chance of developing relapse within 3 months. Additional serum tests for hypoalbuminemia and micronutrient deficiencies, such as iron, vitamin D, B12, B6, folate, selenium, and zinc can aid in diagnosis." [Dolinger et al. 2024]
There are blood tests available for all of these nutrients (iron, vitamin D, B12, B6, folate, selenium, and zinc).
Medication
"The mainstay of therapy for Crohn’s disease in adults is suppression of the immune system. However, even newer selective drugs cause immune suppression and side-effects, and are associated with high costs." [Yanai et al. 2022]
"[...] these drugs might be unnecessary for milder or uncomplicated disease if effective alternatives
are available. Dietary therapy might be ideal for patients with milder disease or as a bridge to medical therapy if there is a delay in instituting medical therapy, and might address the involvement of diet as a trigger of inflammation." [Yanai et al. 2022]
"[...] these drugs might be unnecessary for milder or uncomplicated disease if effective alternatives
are available. Dietary therapy might be ideal for patients with milder disease or as a bridge to medical therapy if there is a delay in instituting medical therapy, and might address the involvement of diet as a trigger of inflammation." [Yanai et al. 2022]
"This case study describes a young adult male with newly diagnosed CD [Crohn's disease] who failed to enter clinical remission [symptom improvement] despite standard medical therapy. After switching to a diet based exclusively on grains, legumes, vegetables, and fruits, he entered clinical remission without need for medication and showed no signs of CD on follow-up colonoscopy." [Sanderfur et al. 2019 (published in Nutrients, unfortunately)]
P.S.: Polymeric diet
There's also a polymeric diet [Borelli et al. 2006], i.e., a formula powder, by Nestlé called "Modulen IBD" for children. It's not vegan but vegetarian (it contains no fish oil!). It basically consists of protein, fat (including some alpha-linolenic acid), glucose, and a multi-vitamin-multi-mineral-mix, and it is very expensive.
The ingredients are: Glucose syrup, milk protein, sucrose, water-free milk fat, medium-chain triglycerides, minerals (magnesium chloride, calcium phosphate, sodium citrate, potassium citrate, potassium hydroxide, calcium carbonate, potassium chloride, manganese sulfate, iron sulfate, zinc sulfate, copper sulfate, sodium molybdate, chromium chloride, potassium iodide, sodium selenate), emulsifier (soya lecithin), corn oil, vitamins (C, E, niacin, pantothenic acid, B6, thiamin, A, riboflavin, folic acid, K, biotin, D, B12), choline bitartrate.
I don't see why this could not be replaced with a generic vegan multivitamin-multimineral (like the one by Deva) and a mix of vegan protein powder, healthy oils, and sugar or rice malt syrup or maple syrup (or blended fruit if tolerated), or alternatively some added starch (cornstarch) or blended/soft grains (gluten-free if gluten is not tolerated).