Malnutrition in Patients with Inflammatory Bowel Disease (IBD)

By Dennis Gibson, MD, FACP, CEDS

Inflammatory Bowel Disease & Malnutrition

Inflammatory bowel disease is a group of disorders that cause chronic inflammation and irritation of the intestinal tract. The two most common diseases are Crohn’s disease (CD) and ulcerative colitis (UC). Crohn’s disease is an autoimmune condition that can affect the entire digestive tract, causing unpleasant symptoms including diarrhea, stomach cramps and abdominal pain. Ulcerative colitis specifically affects the colon, causing inflammation and ulcers that can cause symptoms like bloody stool and abdominal cramping.

It’s reported that up to 85% of those with IBDs also suffer from malnutrition. Uncomfortable and painful gastrointestinal symptoms as well as complications developing as a result of IBDs such as malabsorption and bacterial overgrowth, can contribute to reduced food intake and malnutrition in patients living with inflammatory bowel disease.

Because poor nutrition status and sarcopenia have been shown to affect clinical outcomes, response to therapy and quality of life in patients with inflammatory bowel disease, successful nutritional rehabilitation for patients with IBD is of the utmost importance for managing the condition.

Contributors to Malnutrition in IBD Patients

The two main contributors to malnutrition in patients with inflammatory bowel disease are reduction in food intake and malabsorption. Together these create a problematic cycle of patients eating too little while also being unable to adequately absorb nutrients from the small amount of food they’re eating. Inflammation associated with these conditions can also further increase the body’s metabolic needs.

Reduction of Food Intake

Reduction of food intake is the main contributor to malnutrition in patients with IBD. Patients with an active inflammatory bowel disease can experience nausea, vomiting, abdominal pain, diarrhea and other uncomfortable and painful gastrointestinal complications, causing a loss of appetite. Patients with IBD may restrict their diet to avoid flares or may be frequently admitted to the hospital, which may lead to a reduction in food intake long-term. Additionally, medications frequently used to treat inflammatory bowel disease may also induce nausea, vomiting or loss of appetite, exacerbating reduced food intake.


Malabsorption can be caused through a variety of means, including bowel resection surgery, bacterial overgrowth in the small intestine and chronic bowel inflammation.

Bowel Resection Surgery

Surgery greatly affects nutrition absorption by inducing diarrhea. Bowel resection surgery involves removing a portion of the small or large intestine. Small intestine resection surgery causes reduced digestion and nutrition malabsorption and can also contribute to reduced intestinal uptake of bile acids, which can cause steatorrhea (malabsorption of fats). A partial colectomy (removal of some of the large intestine) is generally well tolerated but can be associated with a small increase in stool frequency due to a reduction in fluid absorption.

Small Intestinal Bacterial Overgrowth

A hallmark of inflammatory bowel disease is small intestinal bacterial overgrowth, which contributes to nutrition malabsorption. Small intestinal bacterial overgrowth may contribute to increased intestinal permeability, reduce the digestion and absorption of nutrients and produce osmotically active metabolites that cause discomfort. Combined, these can cause accelerated gastrointestinal transit that can contribute to malabsorption.

Chronic Bowel Inflammation

Chronic bowel inflammation can also cause malabsorption by accelerating intestinal transit and therefore limiting nutrient absorption, resulting in greater stool volume and diarrhea.

Malnutrition Complications in Patients with IBD

Malnutrition is one of the leading factors in poor clinical outcomes in patients with inflammatory bowel disease. The extent of malnutrition depends on the duration, severity and activity of the disease. Some of the most common complications of malnutrition in patients with IBD include anemia, sarcopenia, low bone mineral density and vitamin deficiencies.


Anemia, an abnormally low level of red blood cells, is the most common extraintestinal manifestation of inflammatory bowel disease. Inflammation, intestinal blood loss, reduced iron absorption and altered iron metabolism all contribute to anemia in patients with IBD. Vitamin B12 deficiency can also cause anemia, and it is more likely to develop in those with Crohn’s disease due to the small intestinal involvement, specifically the ileum (where B12 is largely absorbed).[AR1] 

Loss of Muscle Mass (Sarcopenia)

The loss of muscle mass is a crucial variable in assessing patients with inflammatory bowel disease. A significant portion of patients with IBD have decreased muscle mass, affecting up to 60% of patients. Of those patients, around 40% of them present at a normal body mass index (BMI) and 20% are overweight or obese. Many providers would not be able to identify these patients as undernourished using traditional measures, highlighting the importance of screening all IBD patients for malnutrition even if they do not have a low BMI or bodyweight.

Osteoporosis & Osteopenia

A combination of corticosteroid exposure that is often used to treatment Crohn’s and ulcerative colitis, chronic inflammation, lack of physical activity, sarcopenia and vitamin deficiencies contribute to low bone mass and density. Between 20-50% of patients with IBD also have low bone mass or osteoporosis (low bone mineral density).

Vitamin Deficiencies

Patients with inflammatory bowel disease are often low in both folic acid, vitamin B12 and other vitamins.

Low Folic Acid (Vitamin B9 or Folate)

Folic acid deficiency is common in patients with inflammatory bowel disease, affecting around 9% of patients with ulcerative colitis and 29% of patients with Crohn’s disease. Folate is typically caused by inadequate dietary intake and/or malabsorption.  It can also be caused by pharmaceutical interventions like sulfasalazine and methotrexate, medications used to treat these conditions, which inhibit folate absorption. Low folate can lead to hyperhomocysteinemia (excessive homocysteine), and markedly elevated levels of homocysteine canputpatients at risk for cardiovascular disease and may contribute to arterial and venous thromboembolic events. Folate deficiency is also a risk factor of colorectal cancer in patients with IBD.

Low Vitamin B12

Patients with IBD are also at risk for vitamin B12 deficiency. It is most common in patients with Crohn’s disease, since absorption relies on the ileum. Patients with CD that have had an ileum resection surgery greater than 60 centimeters often develop low B12 and require lifelong B12 replacement.  

Other Vitamin Deficiencies

Patients with IBD are also at risk for other vitamin deficiencies, including calcium, vitamin D, magnesium vitamin A, zinc and vitamin K.

Treating Malnourished Patients with IBD

Screening & Treating Vitamin Deficiencies

Screening patients with IBD, especially if they’ve undergone a resection surgery, is important to avoid clinical complications. Patients who have gotten an ileal resection greater than 20 centimeters should be given B12 replacement and patients with an ileal resection of less than 20 centimeters should receive yearly monitoring.

Because of the implications of vitamin D and calcium on bone mass and bone mineral density, serum calcium and 25(OH) vitamin D should be monitored and supplemented. Adequate vitamin D may also benefit Crohn’s disease.

Other vitamin deficiencies should be monitored and supplemented as necessary.

Nutrition Therapy

In patients with reduced oral food intake, enteral nutrition (EN) therapy, alongside oral nutritional supplements, may be necessary. EN is the preferred method of nutrition therapy over parenteral nutrition (PN) for its lowered incidence of complications.

Parenteral nutritional is beneficial for patients with short bowel syndrome with severe malabsorption that cannot be managed with EN. It also recommended for patients with obstructive disease where feeding tube placement has failed or cannot be placed past the obstruction while awaiting more definitive intervention (such as surgery). It could also be considered short-term for individuals experiencing symptomatic flare ups.


Written by

Dennis Gibson, MD, FACP, CEDS

Dennis Gibson, MD, FACP, CEDS serves as the Clinical Operations Director at ACUTE. Dr. Gibson joined ACUTE in 2017 and has since dedicated his clinical efforts to the life-saving medical care of…

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