The Ultimate Guide to IBD
What is IBD?
Inflammatory Bowel Disease (IBD) refers to a group of long term, relapsing, inflammatory conditions of the digestive tract, involving the body’s immune system attacking its own cells, most notably Ulcerative Colitis (UC) and Crohn’s Disease (CD), each with its own unique features and symptoms, that affect millions of people throughout the word (Glassner et al. 2020, p. 1; US Centres for Disease Control and Prevention (CDC), 2024a, p. 1).
According to Mcdowell et al. (2023, p. 1), Ulcerative Colitis affects the inner lining of the colon and rectum causing complete damage to the lining, whereas Crohn’s Disease, can affect any part of the digestive tract from the mouth to the anus and causes patches of damage potentially reaching the outer lining.
The Effects of IBD
While complications associated with IBD can be serious, most people can manage the disease and lead a relatively normal life.
With Ulcerative Colitis, the inner walls of colon become weak and inflamed, resulting in swelling, the formation of ulcers, stool with blood or mucous, stomach cramping when going to the toilet, and the urgent need to have a bowel movement (CDC, 2024b, p. 1).
In relation to Crohn’s Disease, the walls of the intestines may thicken leading to the formation of cracks and inflamed patches, as well as abdominal pains, diarrhea, malnutrition, mouth sores, ulcers and tears in the anus (CDC, 2024c, p. 1).
Both conditions occur in people who are genetically susceptible after an amplified immune response to stimuli such as food and normal gut bacteria; both are currently incurable diseases and increase the risk of colorectal cancer (McDowell et.al., 2023, p. 1).
Malnutrition is a likely consequence of IBD especially if the condition inflames and injures the small intestine. IBD can interfere with how well food is digested and nutrients absorbed, food avoidance/ restriction because of the disease can also exacerbate malnutrition and nutritional deficiencies in iron, zinc, magnesium, Vitamin B9, B12 and D, are observed in IBD patients (Jablonska & Mrowiec, 2023, p. 1).
What Causes IBD?
Whilst the exact cause of IBD is largely unknown, researchers surmise that it is due to a combination of influences coming together. According to Glassner et al. (2020, p. 1), IBD may eventuate in a host that is genetically susceptible because of environmental and microbial factors and the associated immune response. With more than 200 gene mutations potentially associated with IBD, a person may inherit risk factors that influence the composition of different microbes in the gastrointestinal tract, as well as impact how the body responds to infections and inflammation (CDC, 2024a, p. 1).
Environmental factors are broadly implicated because of countries becoming industrialised, leading to practices that may increase the risk of IBD via disruption in the balance of gut microbes by eating more ultra processed foods and using medications such as oral contraceptives, non-steroidal anti-inflammatory drugs and air pollution (CDC, 2024a, p. 1; Jablonska & Mrowiec, 2023, Pathogenesis of IBD, para. 1). Other environmental factors include xenobiotics, exposure to gastroenteritis, early antibiotic exposure, lack of breastfeeding, cigarette smoking, diet (shift from plant based to processed meat diets), social and psychological stress and excessive hygiene practices during childhood resulting in the lack of exposure to a range of microbes to train the immune system (Glassner et al., 2020 Environmental risk factors and the microbiome, para. 1; Shan et al., 2022, Diet, lifestyle and environmental factors, para. 1; Jablonska & Mrowiec, 2023, Pathogenesis of IBD, para. 1).
IBD and the Gut Microbiome
The gut microbiome is a term used to describe the entirety of microbes (and their genes) living in the digestive tract including bacteria, viruses, protozoa and fungi with over 1000 species of bacteria playing pivotal roles such as maintaining homeostasis (balance), nutrient production, digestion, metabolism, immune function and defence against pathogens (Qiu, et al., 2022, p. 1).
No specific gut bacteria have been shown to cause IBD but when compared to gut microbiota samples of healthy individuals there is a reduced amount of anti- inflammatory types (beneficial) and increased number of inflammatory types (detrimental) (Qiu, et al., 2022, p. 1). This phenomenon is commonly referred to as gut dysbiosis.
The intestinal immune system is key to the development of IBD. In healthy individuals, the intestinal barrier prevents excessive exposure to gut microbes. However, in IBD, there can be a failure of the barrier function, which may result in severe inflammation, leading to increased contact with intestinal microbes and a worsening cycle of inflammation (McDowell et al., 2023, p. 1). Unrestrained inflammatory responses to food particles or normal gut bacteria are considered the main causes of chronic intestinal inflammation and tissue damage in IBD patients (Zhang, 2022, Diet, the Microbiome, and the Intestinal Mucosal Immune System, para. 1).
Metabolites produced by the gut microbiome play a significant role in the context of IBD. Short chain fatty acids (SCFAs) produced by the gut microbiome have been shown to modulate protective immune function and reduce tissue inflammation (Furusawa et al., 2013; Kim et al., 2013 as cited in Liu et al., 2021, Potentially protective bacterial pathways and species, para. 2). According to Liu et al. (2021, Conclusion, para. 4), SCFAs, particularly butyrate, promote the development of a type of immune cell called Treg cells and mucus production to down-regulate inflammatory signalling pathways and to strengthen the gut lining.
Nutrition
A standard western diet which typically includes a high intake of red meat, dairy products, refined grains, sugary drinks, ultra processed foods and a low intake of fruits and vegetables is a risk factor for the development of IBD (CDC, 2024a, p. 1). Food additives widely used in processed foods such as emulsifiers may be detrimental to the gut microbiome and lining and thus contribute to inflammatory diseases. (Zhang, 2022, Dysbiosis in IBD and Gut Microbiome-Targeted Therapies, para. 1).
Several dietary interventions have been researched and know to induce IBD remission. These include Exclusive enteral nutrition (EEN), The Crohn’s disease exclusion diet (CDED), Partial enteral nutrition, CD-TREAT, Low FODMAP diet, Specific carbohydrate diet and Low-Fat diet with researchers suggesting that gut microbiome manipulation is associate with the success of these dietary therapies in reducing inflammation (Sugihara & Kamada, 2021, Dietary Intervention, para. 1-3).
Dietary fibre intake is an important nutritional consideration in the management of IBD as beneficial bacteria convert fermentable fibres (Prebiotics) into SCFAs. In a healthy, diverse gut microbiome, there is a balance between the microbes and the mucous lining of the gut. Certain microbes can degrade the mucous lining as a food source when dietary fibre is inadequate resulting in the thinning of the lining and subsequent leaky gut (and influx of lipopolysaccharides) which is involved in the development of IBD (Zhang, 2022, Diet, the Microbiome, and the Intestinal Barrier, para. 3). According to Slingerland et al. (2017, Prebiotics and IBD, para. 1) two separate studies using a high fibre diet and a prebiotic germinated barley foodstuff exhibited promising results in the management if IBD.
There have been favourable studies on the administration of probiotics in the context of IBD. These include Escherichia coli Nissle 1917, VSL#3, Lactobacillus reuteri, and a combination of Bifidobacterium breve and Beta- galactooligosaccharide prebiotic (Slingerland et al., 2017, Probiotics and UC, para. 1-3). A novel postbiotic preparation with Bifidobacterium Breve BB091109 demonstrated positive results in reducing gut inflammation markers (Motei et al., 2023, p. 1)
Other promising dietary interventions include the moderation of trans and saturated fats, omega 6 fatty acids and artificial sweeteners as well as fostering a diet rich in diverse, polyphenol rich plant foods like fruits and vegetables and omega 3 fatty acids which can be sourced from fatty fish (Saha & Patel, 2023, Conclusion, para. 1)
Due to deficiencies in iron, zinc, magnesium, vitamin B9, B12 and D, observed in IBD patients (Jablonska & Mrowiec, 2023, p. 1), the amounts acquired from diet or supplementation should at minimum meet the recommended dietary intake.
Overall, a well-balanced, wholefood diet void of food additives and rich in fibre and the use the specific probiotics, prebiotics and postbiotics may help foster a healthy gut microbiome with a diverse and balanced composition to reduce the risk of developing chronic gut inflammation. Stress management is another important area to address.
References:
- Glassner, KL., Abraham, PB., & Quigley, EMM. (2020). The microbiome and inflammatory bowel disease, Journal of Allergy and Clinical Immunology, Volume 145, Issue 1, https://doi.org/10.1016/j.jaci.2019.11.003
- Jabłońska, B., & Mrowiec, S. (2023). Nutritional Status and Its Detection in Patients with Inflammatory Bowel Diseases. Nutrients, 15(8), 1991. https://doi.org/10.3390/nu15081991
- Liu, S., Zhao, W., Lan, P., & Mou, X. The microbiome in inflammatory bowel diseases: from pathogenesis to therapy, Protein & Cell Volume 12, Issue 5, May 2021, Pages 331–345, https://doi.org/10.1007/s13238-020-00745-3
- McDowell C., Farooq U., & Haseeb M. Inflammatory Bowel Disease. (2023 Aug 4). In: StatPearls [Internet] . Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470312/
- Motei, DE., Beteri, B., Hepsomali, P., Tzortzis, G., Vulevic, J., & Costabile, A. (2023). Supplementation with postbiotic from Bifidobacterium Breve BB091109 improves inflammatory status and endocrine function in healthy females: a randomised, double-blind, placebo-controlled, parallel-groups study. Front. Microbiol. 14:1273861. https://doi.org/10.3389/fmicb.2023.1273861
- Qiu, P., Ishimoto, T., Fu, L., Zhang, J., Zhang, Z., & Liu, Y. (2022). The Gut Microbiota in Inflammatory Bowel Disease. Frontiers in cellular and infection microbiology, 12, 733992. https://doi.org/10.3389/fcimb.2022.733992
- Saha, S., & Patel, N. (2023). What Should I Eat? Dietary Recommendations for Patients with Inflammatory Bowel Disease. Nutrients, 15(4), 896. https://doi.org/10.3390/nu15040896
- Shan, Y., Lee, M., & Chang, EB. (2022). The Gut Microbiome and Inflammatory Bowel Diseases. Annual Review of Medicine, Volume 73. https://doi.org/10.1146/annurev-med-042320-021020
- Slingerland, AE., Schwabkey, Z., Wiesnoski, DH., & Jenq, RR. (2017) Clinical Evidence for the Microbiome in Inflammatory Diseases. Front. Immunol. 8:400. https://doi.org/10.3389/fimmu.2017.00400
- Sugihara, K., & Kamada, N. (2021). Diet-Microbiota Interactions in Inflammatory Bowel Disease. Nutrients, 13(5), 1533. https://doi.org/10.3390/nu13051533
- US Centres for Disease Control and Prevention. (2024a, June 21, 2024) https://www.cdc.gov/inflammatory-bowel-disease/causes/index.html
- US Centres for Disease Control and Prevention. (2024b, June 21, 2024) https://www.cdc.gov/inflammatory-bowel-disease/about/ulcerative-colitis-uc-basics.html
- US Centres for Disease Control and Prevention. (2024c, June 21, 2024) https://www.cdc.gov/inflammatory-bowel-disease/about/crohns-disease-basics.html
- Zhang P. (2022). Influence of Foods and Nutrition on the Gut Microbiome and Implications for Intestinal Health. International journal of molecular sciences, 23(17), 9588. https://doi.org/10.3390/ijms23179588
