Crohn’s appear to be a microbiota(gut bacteria) dysfunction, which appears to be the case for several autoimmune diseases. Each person microbiota is unique and correlates with their DNA. A diet that works for one patient may not work for another. The following notes are obtained by reviewing PubMed. Note that words like “appears“,”potential” and “may” usually indicate subject beliefs and not objective statistically significant results. In general such speculation is noted by the use of italic in the citation.
While the focus is on Crohn’s, likely the most extreme of microbiota dysfunctions, this information may be relevant to IBS , UC and CFS.
- “Adolescent diet is associated with risk of CD, but not UC, offering insights into disease pathogenesis.” 
- “In Crohn’s disease, an inadequate dietary intake is correlated with nutritional status and disease activity…. Energy intakes were significantly lower in patients with Crohn’s disease“ – this may be a chicken and egg, because of severity less energy is consumed.
- ” there are no defined diets able to improve the disease course, and in Crohn’s disease, supplementation with omega-3 fatty acids did not show a significant benefit.” 
- “general antibiotic use was associated with a reduced risk of relapse in CD.
- High levels of stress were positively associated with relapse, although psychological interventions did not have therapeutic benefits.
- The limited work on diet has reported sulphur-containing foods are positively associated with relapse in UC, but there is no work in CD.
- Ecological data reported positive correlations between air pollution levels and IBD hospitalisations.”
- “Of these, sweet potatoes had the highest reported frequency of beneficial responses. We also identified 4 foods with detrimental effects in more than 25% of our study population. These were mustard, wasabi, and raw and cooked tomatoes” 
- ” margarine, pasta, fried foods, fat, olives [and olive oil], sugar (increased risk), and yogurt, honey, fruits, nuts, fish, and citrus fruits (decreased risk).” 
- “The current evidence is not sufficient to draw firm conclusions on the role of specific food components or nutrients in the aetiology of IBD.” 
- ” Patient-targeted dietary recommendations focus on food restrictions and are highly conflicting.” 
- “There is little evidence from interventional studies to support specific dietary recommendations” 
- ” geographical variation in CD correlates with emulsifier consumption as does the increasing incidence of CD in Japan; … very small concentrations of the emulsifier polysorbate 80 enhance bacterial translocation across intestinal epithelia.” 
- ” Dairy products with a high fat content were most frequently reported to worsen perceived CD symptoms.”
- “500 mg [of curcumin/turmeric] twice per day for 3 weeks …The Crohn’s patients score dropped from 5 to 0 suggesting improvement. No participants experienced a relapse or worsening of symptoms while on the study medication.” [2013 Full Text]
- “more of the New Zealand CD cases report intolerance to maize and mushrooms than those who report beneficial effects or no differences.” 
- ” Second, more robust investigation of the inadequately tested IBD-fiber hypothesis of the 1980s should follow this demonstration of acceptance, tolerance, and appreciation of a fiber-rich diet by individuals with active CD symptoms.” 
- “results were inconsistent for dietary fibre in UC and CD and grain-derived products in UC” 
- “Results demonstrated that consuming a wheat bran-inclusive diet was feasible and caused no adverse effects, and participants consuming whole wheat bran in the diet reported improved health-related quality of life (p = .028) and gastrointestinal function (p = .008) compared to the attention control group.” 
- “Dietary fibre (particularly fruits and vegetables), saturated fats, depression and impaired sleep, and low vitamin D levels have all been associated with incident IBD.”  – in other studies fruit fibre had no positive effect while vegetable fibre correlated with improvement.
- “Dietary fiber (fruits and vegetables) was associated with a reduced risk for CD in the Nurses’ Health Study, but insoluble fiber (whole grain and bran) did not have the same association.47” 
- “Based on data from the Nurses’ Health Study, long-term intake of dietary fiber, particularly from fruit, is associated with lower risk of CD but not UC.” 
- ” patients with Crohn’s disease may be more sensitive to inulin intake” 
- High amount of dietary fiber not harmful but favorable for Crohn disease. 
- “food intolerances are very frequent, but usually inconsistent among IBD patients, and therefore no general dietary recommendations can be made in these patients.
- Low-fat diets seem to be particularly useful.
- Also, some lipid sources, such as olive oil, medium-chain triglycerides, and perhaps omega-3 fatty acids, might have a therapeutic effect.
- Fermentable fiber may have a role in preventing relapses in inactive UC.”
- “Controlled studies of patients receiving enteral nutrition and observations made from patients on exclusion diets have shown that components of whole foods can have deleterious effects for patients with IBD.” 
- “Exclusion of sugar shows little evidence of amelioration in CD. Omega 3 fatty acids show promise in the treatment of IBD but await larger randomized controlled trials.” 
- “It is proposed that eradication of these microbes[Klebsiella] by the use of antibiotics and low starch diet, in addition to the currently used treatment, could help in alleviating or halting the disease process in CD.”
- “A high intake of dietary long-chain n-3 PUFAs[polyunsaturated fatty acids] may be associated with a reduced risk of UC. In contrast, high intake of trans-unsaturated fats may be associated with an increased risk of UC.” 
- “High dietary intakes of total fats, PUFAs, omega-6 fatty acids, and meat were associated with an increased risk of CD and UC. High fiber and fruit intakes were associated with decreased CD risk, and high vegetable intake was associated with decreased UC risk.” 
- ” A small number of foods are frequently considered to be beneficial, including white fish, salmon and tuna, gluten-free products, oatmeal, bananas, boiled potatoes, sweet potatoes (kumara), pumpkin, soya milk, goat’s milk and yoghurt.
- Foods that are typically considered detrimental include grapefruit, chilli or chilli sauce, corn and corn products, peanuts, cream, salami, curried foods, cola drinks, high energy drinks, beer, and red wine.
- For a number of the food items, the same item that was beneficial for one group of subjects was detrimental to others; in particular soya milk, goat’s milk, yoghurt, oatmeal, kiwifruit, prunes, apple, broccoli, cauliflower, linseed, pumpkin seed, sunflower seed, ginger and ginger products, beef, lamb, liver, and oily fish.
- It was not possible to identify a specific group of food items that should be avoided by all CD patients.” 
Enteral Nutrition (EN)
“Enteral nutrition [tube feeding]: A way to provide food through a tube placed in the nose, the stomach, or the small intestine. A tube in the nose is called a nasogastric tube or nasoenteral tube.” [Source]
- ” In all studies, patients used EN as a supplement or as a nocturnal tube feeding in addition to their normal food.. maintained clinical remission rate at 1 year was significantly higher in patients treated with EN in four of the six studies.”
- ” A non significant trend favouring very low fat and/or very low long chain triglyceride content exists but larger trials are required” 
- “The outcomes of this prospective study showed that concomitant EN during infliximab maintenance therapy does not significantly increase the maintenance rate of clinical remission in patients with CD.” 
- “The use of specialized enteral nutrition therapy in combination with infliximab appears to be more effective at inducing and maintaining clinical remission among patients with Crohn’s disease than infliximab monotherapy.” 
- “Limited evidence indicates potential benefits of elemental nutrition against no intervention in the maintenance of remission and prevention of relapse in adult patients with CD.” 
- ” studies have shown that exclusive enteral nutrition can induce remission in mild-to-moderate disease comparable to corticosteroids.” 
- ” Partial enteral nutrition (PEN) with free diet is ineffective for inducing remission, suggesting that the mechanism depends on exclusion of free diet. We developed an alternative dietbased on PEN with exclusion of dietary components hypothesized to affect the microbiome or intestinal permeability.” 
- Conflicting results on the efficacy of enteral nutrition during infliximab maintenance therapy forCrohn‘s disease are correct.
Parenteral Nutrition Diet(TPN)
- “TPN has limited effects on IBD” 
- ” There is no significant difference in the efficacy of elemental and non-elemental diets for induction of remission of Crohn’s disease.”
- “Limited evidence indicates potential benefits [no firm evidence] of elemental nutrition against no intervention in the maintenance of remission and prevention of relapse in adult patients with CD.” 
- “elemental diet cannot be recommended for the routine treatment of active pouchitis.” 
- ” Species diversity was reduced by total parenteral nutrition, but not by elemental diet.” 
- “Relapse rates with an “elemental diet” occur at the rate of 27% at one year,2 whereas the control group rate is 60% to 70% in the studies by Takagi et al2 and Sandborn et al.” 
Gluten Free Diet [GFD]
- “Overall 65.6% of all patients, who attempted a GFD, described an improvement of their gastrointestinal symptoms and 38.3% reported fewer or less severe IBD flares. In patients currently attempting a GFD, excellent adherence was associated with significant improvement of fatigue (P < 0.03).” 
- Alicam (main part is Whey) produced remission 
- “Whey protein intake resulted in significant differences, such as improvement in Lean Body Mass and reduction in Fat percentage.” 
- “Glutamine and whey protein improve intestinal permeability and morphology in patients with Crohn‘s disease: a randomized controlled trial. 
- “[Whey based formula] significantly decrease disease activity in children with Crohn‘s disease.” 
Note: Many commercial formula for Whey includes stevia which should not be used (increases inflammation in CD).
low Fermentable, Oligosaccharides, Disaccharides, Monosaccharides And Polyols (FODMAP) diet
- “(FODMAP) diet may improve symptoms but there are currently no data to suggest that these approaches have any role in the induction or maintenance of remission.” 
- HIGH FODMAP makes CFS/IBS/FM worst. Low FODMAP reduces histamines and improves CBS/IBS/FM. See this post.
Semi-Vegetarian Diet (SVD)
- ” Our SVD contains 32.4 g of dietary fiber in 2000 kcal. There was no untoward effect of the SVD. The remission rate with combined infliximab and SVD for newly diagnosed CD patients was 100%. Maintenance of remission on SVD without scheduled maintenance therapy with biologic drugs was 92% at 2 years.” 
- “Relapse rates at 1 year and 2 years were 0% and 8% in patients on SVD and 33% and 75% in patients on an omnivorous diet.” 
- ” Remission was maintained in 15 of 16 patients (94%) in the SVD group vs two of six (33%) in the omnivorous group” 
“About 800 or 1100 kcal/d was given in the beginning, and calories were gradually increased to a maximum of about 30 kcal/kg standard body weight. White rice was served first for 2-5 d followed by mixed rice (70% white rice and 30% unrefined whole brown rice) for 2-5 d, and finally brown rice was served. Unrefined brown rice contains more vitamins and minerals than white rice (Figure (Figure1)1) and is reported to increase significantly beneficial bacteria compared to well-milled white rice. Eggs and milk were used. In other words, our diet was a lacto-ovo-vegetarian diet. Miso (fermented bean paste) soup, vegetables, fruits, legumes, potatoes, pickled vegetables, and plain yoghurt were served daily. Fish was served once a week and meat once every 2 wk, both at about a half the average amount. Patients were provided with several different 4-wk menus on a rotational basis. Figure Figure22 shows what an SVD looks like. Details of the contents of nutritional elements including minerals, vitamins, and fatty acids in an SVD are shown in Table Table4.4. These figures were obtained by HOPE/COMETY-NT (Fujitsu, Tokyo, Japan). The rate of fat in total calories (18.6%) was < 20%, which is the lower limit of Dietary Reference Intakes for Japanese (DRI). The amounts of dietary fiber and iron in the SVD were above the DRI. Those of most of the other elements in the SVD were comparable to DRI (Table (Table4).4). Coarse tea was served along with the meal service. During hospitalization, foods other than the meal service were discouraged. Drinking of green tea was encouraged. Participant days of SVD ranged from 43 to 82 d (median: 49 d) in medically treated patients (Table (Table1).1)” 
Japanese Diet for CD
“However, in our clinical practice at Keio University Hospital, which treats > 2,000 IBD patients, we have explained recently published findings on the roles of dietary fiber in the suppression of inflammation to patients, and have recommended that these patients consume more dietary fiber, including fruits, vegetables, seaweeds, dried mushrooms and dried Japanese radishes…we recommend that IBD patients consume boiled rice together with an individually acceptable proportion of barley, which was a historical part of the normal Japanese lifestyle. The goal is to gradually increase the intake of properly balanced soluble and insoluble dietary fiber every month or year, because both the proportion and absolute numbers of fermented probiotics strains are reduced in the intestines of IBD patients. A gradual increase in fermenters may allow patients to handle increased amounts of dietary fiber. The quantity of fermenters present in the intestines of these patients at the beginning of probiotic treatment may be insufficient to handle an overabundance of dietary fiber, resulting in deleterious outcomes, such as intestinal obstruction…..Asian societies are at a crossroads between a Western-style and a traditional high-fiber, low-fat, and fermenter-rich diet. Clinicians should encourage these traditional foods to promote public welfare.” 
- Western diet induces dysbiosis with increased E coli in CEABAC10 mice, alters host barrier function favouring AIEC colonisation.
- “the “Western” diet, which is high in sugar and fat, causes dysbiosis which affects both host GI tract metabolism and immune homeostasis”
The semi-vegetarian diet appears the clear winner for a general diet framework. Inclusion of appropriate fiber appears to be strongly supported (if done gradually) and contradicts the speculation from the 1980’s of fiber being bad which is still believed by many MDs (despite no clear evidence from studies). Special care needs to taken of foods that some CD’ers react to, they should be avoided or tried in small amounts.
And last — the association of autoimmune with the hygiene hypothesis seems supported by this study:
“Multivariate analysis showed that regular fish consumption (OR 0.52, 95% CI 0.33-0.80, p = 0.003), and presence of cattle in the house compound currently (OR 0.57, 95% CI 0.35-0.92, p = 0.023) were significant protective associations, whereas use of safe drinking water was positively associated (OR 1.59, 95% CI 1.02-2.47, p = 0.042) with the disease.”