Malnutrition and irritable bowel disease

The occurrence of malnutrition among people diagnosed with inflammatory bowel disease (IBD) exhibits considerable variability, with reported rates ranging from 20% to 85%. Inflammatory bowel disease (IBD) is a term that describes disorders involving long-standing (chronic) inflammation of tissues in your digestive tract. Types of IBD include ulcerative colitis and Crohn’s disease.


Moreover, recent research findings from 2022 reveal that out of 237 patients with inflammatory bowel disease (IBD) screened for malnutrition, 14% were identified as being at high risk. Specifically, the prevalence of a positive screening was 15% among patients diagnosed with Crohn's disease and 12% among those with ulcerative colitis.

What is malnutrition?

Before delving into the subject, let's explore the definition of the term "malnutrition." Malnutrition refers to deficiencies or excesses in nutrient intake, imbalance of essential nutrients or impaired nutrient utilisation. It can be also described as a lack of proper nutrition, caused by not eating enough or not being able to utilise the food that one eats.

During the course of the disease, protein–energy malnutrition and deficiencies of specific nutrients may represent clinical concerns in IBD patients, and their prevention is essential to avoid complications. Malnutrition is one of the most important factors associated with a poor clinical outcome in patients with IBD. According to some papers, a significant proportion of IBD patients affected by sarcopenia (41.5%) presented a normal body mass index (BMI) and, therefore, would not be identified as undernourished by traditional measures. However a recent study proved again that most of the individuals screened positive for malnutrition had a normal or overweight body mass index, showing that malnutrition risk can develop anywhere.

A systematic review reported that up to 60% of IBD patients have decreased muscle mass when compared with healthy subjects and this can also explain the increased risk of sarcopenia and higher BMI in these patients. Sarcopenia is common in overweight patients with inflammatory bowel disease.

What can cause malnutrition in individuals with IBD?

  • reduced oral nutritional intake
  • malabsorption
  • ongoing loss of blood and proteins
  • the presence of intestinal bacterial overgrowth
  • strictures (when scar tissue builds up after repeated cycles of inflammation and healing in the lining of the intestine)

Various factors contribute to malnutrition in individuals with inflammatory bowel disease (IBD). One primary determinant is the reduced oral intake of food in IBD patients. The reduction in food intake can be attributed to multiple mechanisms. Patients experiencing active IBD often encounter a loss of appetite due to symptoms such as nausea, vomiting, abdominal pain, and diarrhoea. 
Additionally, medications prescribed for IBD can induce nausea, vomiting, or anorexia. The use of glucocorticoids, for instance, may decrease the absorption of phosphorus, zinc, and calcium, potentially leading to osteoporosis. Prolonged sulfasalazine therapy, which acts as a folic acid antagonist, could be associated with anaemia. The most common micronutrient deficiencies in IBD patients concern iron, calcium, selenium, zinc, magnesium, water-soluble vitamins, in particular, B12 and folic acid, and fat-soluble vitamins, such as A, D, and K.

Malabsorption is closely associated with mucosal changes, including compromised epithelial transport and loss of epithelial integrity, among other factors. Studies indicate that in patients with Crohn's disease (CD), the involvement of the ileum significantly contributes to the decreased absorption of nutrients. Specifically, disruptions in ionic transport result in the loss of electrolytes and fluids. Additionally, ongoing inflammation leads to a persistent loss of blood and proteins in the intestinal lumen.

How can IBD cause a lack of appetite?

The symptoms experienced by individuals with inflammatory bowel disease (IBD) can lead to a lack of appetite and alterations in their eating habits and overall dietary patterns. Some individuals may face difficulties reintroducing certain foods into their diet, consequently restricting their overall food intake and diminishing their choices, resulting in a reduced sense of food freedom.

If you consume yoghurt and immediately experience cramps, making it challenging to leave the bathroom, would you still choose to eat that yoghurt? Now imagine the same scenario not with only one food but with plenty more.

Nutritional management of IBD

Treating patients with IBS is quite challenging due to the lack of a well-understood pathophysiology of the disease and the variability of symptom occurrence throughout its course. However, the greatest value in the treatment process is attributed to appropriate nutrition and lifestyle changes.

Since there isn't a universal dietary approach for managing IBD, maintaining a food diary can be crucial. What works for one individual might not be effective for another, so understanding how your body reacts to different foods can aid in symptom management. Keeping track of foods that worsen symptoms and those that alleviate them is recommended. A nutrition specialist can assist in identifying triggers for your symptoms and offering guidance on necessary lifestyle adjustments.

Balanced diet

The gut microbiome acts as both a mediator and modifier of the metabolic response to our diet. In the case where the microbiome acts as a mediator, what we consume directly impacts our microbiome, altering its composition and function. As a modifier, the effect of diet on metabolism depends on our microbiome. Therefore, the gut microbiota is susceptible to changes with diet and specific dietary components play a key role in shaping the composition and activity of the microbiota from birth throughout our lives.

Improving gut health through a diverse diet, and consuming more foods from plant sources, is crucial. Studies show that individuals who consume at least 30 different vegetables/fruits per week exhibit greater diversity in their gut microbiota, indicating a better balance of the gut microbiome. The greater the variety in your menu, the more you help your gut produce more diverse enzymes, which are later used to break down the food you've consumed.

This is where individuals with IBD/IBS might face challenges, especially if they have already eliminated numerous foods from their diet. In such cases, they may require guidance from a specialist to navigate the process; otherwise, it can lead to a cycle of frustration and difficulty.

Symptom-specific dietary alterations and fibre

1. Diarrhoea

Diarrhoea stands as a prominent symptom of IBD. When experiencing significant diarrhoea and pain, the urge to stop eating may be strong. However, maintaining adequate nutrition and hydration is crucial. While some individuals notice that certain high-fibre foods exacerbate their diarrhoea, it's advisable to avoid these foods during flare-ups.  

Yet, for certain individuals with a low intake of dietary fibre, boosting fibre intake can also yield positive outcomes. Additionally, spicy, fatty foods, alcohol, and caffeine can also aggravate diarrhoea.

2. Constipation

Increasing fluid intake may aid in forming softer stools that are easier to pass. Additionally, incorporating more fibre into your diet may be helpful, although this approach may not be suitable for everyone. Fibre can play a big part in managing symptoms of IBS. Therefore, a professional may suggest you adjust the amount of fibre in your diet. If constipation concerns you, you might need to discuss it with your doctor and/or dietitian.

Low FODMAP diet

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, which are categories of carbohydrates that are challenging for the gut to absorb and digest, leading to rapid fermentation in the large intestine. This fermentation process generates gases, causing uncomfortable bloating and that’s why some specialists might suggest you try this type of diet.

Low FODMAP is a three-step elimination diet:

  • First, you stop eating certain foods (high FODMAP foods).
  • Next, you slowly reintroduce them to see which ones are troublesome.
  • Once you identify the foods that cause symptoms, you can avoid or limit them while personalising your overall diet

What else can affect your IBD/IBS?

Additional factors that can influence your IBD/IBS include your level of physical activity, stress levels, stress management, hydration status, alcohol intake, quality and duration of sleep, and psychological health.


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The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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Aberdeen, Aberdeenshire, AB22
Written by Derya Hyusein, RD Registered Dietitian | Nutrition Expert | MSc HCPC
Aberdeen, Aberdeenshire, AB22

Derya Hyusein, is a Registered Dietitian with professional credentials in both UK and Bulgaria. She has helped more than 3000 online clients to reach their health and fitness goals through the science of nutrition and exercise. Derya's experience includes helping women with T1D, T2D, malnutrition, obesity and many other conditions.

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