Malnutrition Across GI Conditions

Written by: Rosanna Lee, RD

Updated: July 9th, 2025

Our incredible gastrointestinal (GI) tract is like the unsung hero of our body! It’s responsible for the magical journey of digestion, absorption, and excretion. It’s quite a performer, running the show from “gum to bum” – that’s from your mouth all the way down to your anus, making sure everything runs smoothly.

Now, sometimes our GI tract faces challenges. In certain GI disorders, it might encounter a few roadblocks that can lead to malnutrition. These roadblocks can be due to structural hiccups, like physical damage to the gut, or sometimes, functional causes where the tract doesn’t operate properly. Poor management of inflammatory bowel disease (i.e., Crohn’s disease and ulcerative colitis), celiac disease, gastroparesis, and diverticulitis can result in malnutrition – when your body receives an inadequate supply of nutrients and can lead to deficiencies. In this article we walk you through each of these GI conditions and discuss how they relate to malnutrition.

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Inflammatory Bowel Disease

With inflammatory bowel diseases (IBD) like Crohn’s disease and ulcerative colitis (UC), it is reported that between 20-85% of individuals develop malnutrition because these disorders are chronic (life-long) and have the potential to relapse_¹. This relapse is characterized by chronic inflammation of the GI tract and if untreated, can cause permanent damage.

Crohn’s disease can impact any area of the GI tract, but most commonly affects the end of the small intestine, right before the start of the large intestine².

In UC, inflammation occurs in the large intestine and/or the rectum².

The difference between the two is that in Crohn’s, the inflammation may reach through multiple layers of the walls of the GI tract, whereas in UC, the inflammation is only found in the innermost layer of the colon lining². Crohn’s disease may be characterized by patchy areas of inflammation whereas UC may be more continuous³.

Damage to these areas of the GI tract can cause malabsorption, making it difficult for your body to take in proteins, fats, carbohydrates/sugars, vitamins, and minerals. The severity of malabsorption is determined by how much and where the small intestine is impacted, as this is where the majority of nutrient absorption takes place. If significant parts of the small intestine are inflamed or resected, the greater the influence on nutritional status. If it impacts the final third of the small intestine (called the ileum), the absorption of fat-soluble vitamins like A, D, E, and K, and water-soluble vitamin B12 would likely be affected⁴.

Crohn’s Disease

Individuals with UC may present with fewer or less severe nutritional deficiencies. However, GI issues like diarrhea and/or blood loss can cause weight loss and anemia. Typically, malnutrition is more commonly associated with Crohn’s disease than UC ⁵. For individuals who have had repeated cycles of inflammation and healing along the intestinal lining, scar tissue can build up and cause a stricture. Strictures narrows the passage where digested food travels and may lead to a blockage. High-fibre foods can get stuck in the narrowed areas and cause pain, bloating, nausea, and the inability to pass stool ⁵.

Thus, some individuals may be recommended to adhere to a low fibre/low residue or liquid diet to lessen symptom severity and allow food to pass comfortably through the narrowed area⁶. Medications may also be used to reduce inflammation. Surgery is another option to help remove or repair the stricture.

Symptoms across both GI conditions may present similarly. Severe diarrhea can cause dehydration and electrolyte losses (sodium, potassium, magnesium, phosphorus, and zinc) and can lead to weight loss from malabsorption. Abdominal pain and nausea may reduce your appetite to eat, making it challenging to take in adequate calories and nutrients. The development of ulcers in the intestines may lead to rectal bleeding, which can also lead to iron deficiency or anemia⁵.

Limiting intake to lesson symptoms of diarrhea or bowel movements also increases risk of malnutrition and unintentional weight loss. Certain medications used to treat inflammation in IBD may alter your nutritional status (i.e., methotrexate and sulfasalazine) by decreasing folic acid absorption⁵. Taking a folic acid supplement may be necessary to replace the extra loss of folate.

IBD

Although the exact pathogenesis of IBD is not known, it is now recognized that IBD is a result of a weakened immune system². Its cause has been linked to an incorrect immune response to an environmental trigger(s) (such as bacteria, dietary factors, or a virus) and/or genetic predisposition². Although IBD is not entirely linked to diet, the food we eat plays a crucial role in IBD management and can help achieve remission, lessen symptoms, and optimize nutritional status. Consider minimizing intake of trigger foods that cause unwanted GI symptoms and inflammation⁷.

A low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet may be recommended by your dietitian. This diet cuts out a specific group of carbohydrates that may be poorly absorbed by the GI tract. These may be foods that contain fructose, lactose, sugar alcohols (sorbitol and mannitol), fructans, and galacto-oligosaccharides⁸. Although this diet was originally developed for those who have irritable bowel syndrome, a functional digestive disorder, it has also gained attention for symptom management in IBD. The low FODMAP diet helps reduce symptoms and better understand triggers through elimination, reintroduction, and adaptive phases, and is not meant for long-term use ⁸.

IBD may also be managed by other diets that focus on reducing severity of inflammation by regulating gut bacterial balance with certain foods (i.e., anti-inflammatory diet or IBD-AID, autoimmune protocol diet or AIP, Crohn’s Disease Exclusion Diet)⁸. Risk of malnutrition is high with restrictive diets, so it is highly recommended to seek help from a registered dietitian.

Celiac Disease

Celiac disease (CD) is an autoimmune disease that affects your small intestine and prevents nutrients from being absorbed. Eating products with gluten causes an immune response, damaging the small intestine. Gluten is a protein found in wheat, barley, rye, and triticale (a cross between wheat and rye)⁹.

On a microscopic level, the presence of gluten triggers your immune system to damage villi, which are small, finger-like projections that line your small intestines. The primary role of villi is to transport food nutrients from the inside of the small intestine into the blood⁹. If the villi are destroyed, then nutrients cannot be absorbed and the risk of malnutrition increases¹⁰. Iron deficiency anemia, vitamin B12 deficiency, folate deficiency anemia, and osteoporosis are some of the commonly seen malabsorption conditions¹¹.

Iron, vitamin D, and zinc deficiency may present more often in newly diagnosed celiac patients or in untreated individuals with celiac disease¹¹. It is best to monitor patients for their calcium, iron, magnesium, folate, vitamin B6, vitamin B12, vitamin A, vitamin D, vitamin E, vitamin K, zinc, and copper. Complications of celiac disease may extend to include joint pain, seizures, thinning bones, and cancer.⁹ Following a lifelong gluten-free diet is currently the best practice for those living with celiac disease¹².

Gluten-free Diet

A gluten-free diet means avoiding most grains, pastas, cereals, and processed foods. To ensure adherence to this diet, it is important to read ingredient lists on foods. Food labels may not explicitly list gluten as an ingredient, so it is valuable to know ingredients that also contain gluten. Examples of this include: einkorn, spelt, wheat bran, wheat starch, wheat germ, cracked wheat, kamut, and hydrolyzed wheat protein⁹. Emulsifiers such as dextrin, mono- and di-glycerides, seasonings, and caramel colours may contain gluten⁹.

Always check food labels including beer, bouillon cubes, candy, brown rice syrup, chips, cold cuts, deli meats, fries, gravy, imitation fish, matzo, rice mixes sauces, seasonings, soups, and sauces. Have your pharmacist check to ensure your medications do not contain gluten as it may sometimes be used as an additive in medications. Gluten may also be found in herbal supplements, vitamins, probiotics, and in other natural health products. Gluten can also be in topical items like lip balms, lipsticks, and toothpaste.

Gastroparesis

Gastroparesis is a disorder that is characterized by delayed gastric emptying. The movement of food from your stomach to your small intestine is slowed or stopped even without a blockage in the GI tract⁴. Although there may be many possible causes of gastroparesis, diabetes is one of the most common chronic diseases known to cause this issue⁴. Other possible causes of gastroparesis may include any damage to the vagus nerve hypothyroidism, scleroderma, some autoimmune disorders, nervous system disorders (i.e., Parkinson’s disease, multiple sclerosis), and, or viral infections in the stomach⁴.

Certain medications may also cause delayed gastric emptying or affect the movement of food, giving a sensation that feels like gastroparesis. Therefore, it is best to have your medications reviewed by a pharmacist. Signs and symptoms of gastroparesis may include early satiety, prolonged satiety, nausea, vomiting, bloating, belching, upper abdominal pain, heart burn, reflux, and poor appetite⁴.

Gastroparesis can be managed with dietary interventions to prevent the onset of malnutrition and dehydration. You may be asked to consume foods lower in fat and fibre, eat smaller and more frequent meals, chew your food thoroughly, consume well-cooked soft foods, avoid carbonated drinks/ alcohol, and drink plenty of fluids containing electrolytes and glucose (i.e., oral rehydration solutions, sports drinks, naturally sweetened low-fibre fruit/vegetable juices, low-fat broths/clear soups)⁴.

Multivitamins may also be recommended to meet any gaps in micronutrient intake. In cases where oral intake cannot be tolerated, tube feeding, parenteral or intravenous (IV) nutrition may be provided to support nutritional needs.

Diverticulitis

Diverticulitis is a disease that happens when small pockets in the inside of your large intestine, called diverticula, become inflammed¹³. Inflammation from a tear in the colon lining or from an infection can cause severe pain, distended abdomen, a palpable colon, nausea and vomiting, rectal bleeding, fever, constipation, and sometimes diarrhea¹³.

Inflammation may impair the absorption of electrolytes like sodium, potassium, and chloride. Inadequate electrolyte absorption can impact one’s fluid balance, the body’s pH level, and whether nutrients are moved into the cells and wastes out of the cells¹⁴. It may also impair the colon’s ability to produce B and K vitamins via fermentation by colonic bacteria.

Short-chain fatty acid (SCFA) production may be challenged in the case of diverticulitis since fibre fermentation in the colon can also be impaired¹⁵. SCFAs are used in your intestines for energy, used to reduce inflammation, to absorb minerals, and aid in metabolism among some of its key functions¹⁵. Medications can be used to treat infection and inflammation.

GI rest is often recommended as well to heal the gut. For good gut maintenance, your diet should include adequate fibre so that stools can bulk up to transit easily out through the colon. Fibre helps to reduce incidences of diverticulitis flares. Current fibre recommendations are for females to consume 25 grams of fibre and for males consume 38 grams of fibre daily¹⁶. Contrary to previous recommendations, recent research on fibre and diverticulosis and diverticulitis have found that foods like popcorn, nuts, seeds, and fruits/vegetables with seeds do not cause a problem¹³. However, you may want to avoid these foods if you find they trigger your symptoms.

Managing Malnutrition

Moderate to severe malnutrition may require the use of invasive feeding procedures like tube-feeding or IV nutrition support ^5,17. These procedures provide quick delivery of essential nutrients the body requires for survival, while allowing the gut to rest and heal. Those with the capacity to take foods orally may want to focus on calorically and nutrient-dense foods to restore macro- and micro-nutrient imbalances and weight restoration if significant weight loss has occurred.

Testing and Nutrition

Bloodwork can be used to monitor for refeeding syndrome, and vitamin and mineral deficiencies that require additional supplementation on top of the existing diet¹⁸. IV therapy and/or oral rehydration solutions may be considered if fluid and electrolyte imbalances persist. If appetite is limited, consideration for smaller, more frequent meals or snacks can be included. Nutrition supplements may also be used if meal intake is poor.

A registered dietitian can provide individualized guidance to help you optimize your nutrition while managing your GI symptoms.